USER MANUAL

Manual authors: Willem Ferguson, Jacco van Koll, Dirk Hohndel, Reinout Hoornweg, Linus Torvalds, Miika Turkia, Amit Chaudhuri, Jan Schubert, Salvador Cuñat

Version 4.2, August 2014

Welcome as a user of Subsurface, an advanced dive logging program with extensive infrastructure to describe, organise, interpret and print scuba and free dives. Subsurface offers many advantages over other similar software solutions:

Do you use two different dive computer brands, each with its own proprietary software for downloading dive logs? Do you dive with rebreathers as well as open circuit? Do you use a Reefnet Sensus time-depth recorder in conjunction with a dive computer? Subsurface offers a standard interface for downloading dive logs from all these different pieces of equipment and to store and analyse the dive logs within a unified system.
Do you use more than one operating system? Subsurface is fully compatible with Mac, Linux and Windows, allowing you to access your dive log on each of your operating systems with a single application.
Do you use Linux or Mac and your dive computer has only Windows-based software for downloading dive information (e.g. Mares)? Subsurface provides a way of storing and analysing your dive logs on other operating systems.

Subsurface binaries are available for Windows PCs (Win XP or later), Intel based Macs (OS/X) and many Linux distributions. Subsurface can be built for many more hardware platforms and software environments where Qt and libdivecomputer are available.

The scope of this document is the use of the Subsurface program. To install the software, consult the Downloads page on the Subsurface web site. Please discuss issues with this program by sending an email to our mailing list and report bugs at our bugtracker. For instructions on how to build the software and (if needed) its dependencies please consult the INSTALL file included with the source code.

Audience: Recreational Scuba Divers, Free Divers, Tec Divers, Professional Divers

Table of Contents

1. Start Using the Program

The Subsurface window is usually divided into four panels with a Main Menu (File Import Log View Filter Help) at the top of the window (for Windows and Linux) or the top of the screen (for Mac and Ubuntu Unity). The four panels are:

The Dive List to the bottom left containing a list of all the dives in the user’s dive log. A dive can be selected and highlighted on the dive list by clicking on it. In most situations the up/down keys can be used to switch between dives. The Dive List is an important tool for manipulating a dive log.
The Dive Map to the bottom right, showing the user’s dive sites on a world map and centred on the site of the last dive selected in the Dive List.
The Dive Info to the top left, giving more detailed information on the dive selected in the Dive List, including some statistics for the selected dive or for all highlighted dive(s).
The Dive Profile to the top right, showing a graphical dive profile of the selected dive in the Dive List.

The dividers between panels can be dragged in order to change the size of any of the panels. Subsurface remembers the position of the dividers, so the next time Subsurface starts it uses the positions of the dividers from when the program was last used.

If a dive is selected in the Dive List, the dive location, detailed information and profile of the selected dive are shown in the respective panels. On the other hand, if one highlights more than one dive the last highlighted dive is the selected dive, but summary data of all highlighted dives are shown in the Stats tab of the Dive Info panel (maximum, minimum and average depths, durations, water temperatures and SAC; total time and number of dives selected).

The user can determine which of the four panels are displayed by selecting the View option on the main menu. This feature gives the user several choices of display:

All: show all four of the panels as in the screenshot above.

Divelist: Show only the Dive List.

Profile: Show only the Dive Profile of the selected dive.

Info: Show only the Dive Notes about the last selected dive and statistics for all highlighted dives.

Globe: Show only the world map, centred on the last selected dive.

Like many other functions that can be accessed via the Main Menu, these options can be triggered using keyboard shortcuts. The shortcuts for a particular system are shown with an underline in the main menu entries. Since different Operating Systems and the user chosen language may cause Subsurface to use different shortcut keys they are not listed here in the user manual.

When the program is started for the first time, it shows no information at all. This is because the program doesn’t have any dive information available. In the following sections, the procedures to create a new logbook will be described.

2. Creating a new logbook

Select File → New Logbook from the main menu. All existing dive data are cleared so that new information can be added. If there are unsaved data in an open logbook, the user is asked whether the open logbook should be saved before a new logbook is created.

3. How to store dive information in the user’s logbook

There are several ways in which dive information can be added to a logbook:

Enter dive information by hand. This is typically useful if the diver did not use a dive computer and dives were recorded in a written logbook.
Import dive information directly from a dive computer if it is supported by Subsurface. The latest list of dive computers supported by Subsurface can be found at: Supported dive computers.
Import dive information from another data base or file format. This is discussed in more detail below.

3.1. Entering dive information by hand

This is usually the approach for dives without a dive computer. The basic record of information within Subsurface is a dive. The most important information in a simple dive logbook usually includes dive type, date, time, duration, depth, the names of your dive buddy and of the dive master or dive guide, and some remarks about the dive. Subsurface can store much more information than this for each dive. In order to add a dive to a dive log, select Log → Add Dive from the Main Menu. The program then shows three panels to enter information for a dive: two tabs in the Dive Info panel (Dive Notes and Equipment), as well as the Dive Profile panel that displays a graphical profile of each dive. These panels are respectively marked A, B and C in the figure below. Each of these tabs will now be explained for data entry.

3.1.1. Dive Notes

This panel contains the date, time and place information for a particular dive, environmental conditions, co-divers and buddies, as well as some descriptive information. The message in a blue box at the top of the panel indicates that the dive is being edited. If one clicks on the Dive Notes tab, the following fields are visible:

The Time field reflects the date and the time of the dive. By clicking the date, a calendar is displayed from which one can choose the correct date. Press ESC to escape from the calendar. The time values (hour and minutes) can also be edited directly by clicking on each of them in the text box and by overtyping the information displayed.

Air and water temperatures: the air and water temperatures during the dive can be typed directly on the fields to the right of the Start time. Temperature units are not needed, as they will be automatically supplied by Subsurface. Only the numerical value must be typed by the user (The units selected in the Preferences will determine whether metric or imperial units are used).

Location: Here the name of the dive site can be entered, e.g. "Tihany, Lake Balaton, Hungary". Auto completion of location names will make this easier if one frequently dives at the same sites.

Coordinates: The geographic coordinates of the dive site should be entered here. These can come from three sources:

One can find the coordinates on the world map in the bottom right hand part of the Subsurface window. The map displays a green bar indicating "No location data - Move the map and double-click to set the dive location". Upon a double-click at the appropriate place, the green bar disappears and the coordinates are stored.
The coordinates can be obtained from the Subsurface Companion app if the user has an Android device with GPS and if the coordinates of the dive site were stored using that device. Click here for more information

The coordinates can be entered by hand if they are known, using one of four formats with latitude followed by longitude:

ISO 6709 Annex D format e.g. 30°13'28.9"N 30°49'1.5"E
Degrees and decimal minutes, e.g. N30° 13.49760' , E30° 49.30788'
Degrees minutes seconds, e.g. N30° 13' 29.8" , E30° 49' 1.5"
Decimal degrees, e.g. 30.22496 , 30.821798

Southern hemisphere latitudes are given with a S, e.g. S30°, or with a negative value, e.g. -30.22496. Similarly western longitudes are given with a W, e.g. W07°, or with a negative value, e.g. -7.34323.

Please note that GPS coordinates of a dive site are linked to the Location name - so adding coordinates to dives that do not have a location description will cause unexpected behaviour (Subsurface will think that all of these dives have the same location and try to keep their GPS coordinates the same).

Divemaster: The name of the dive master or dive guide for this dive can be entered here. Again, this field offers auto completion based on the list of dive masters in the current logbook.

Buddy: In this field one can enter the name(s) of the buddy / buddies (separated by commas) who accompanied the user on the dive. Auto completion is offered based on the list of buddies in the current logbook.

Suit: The type of diving suit used for the dive can be entered here. As with the other items, auto completion of the suit description is available. Some dry-suit users may choose to use this field to record what combination of suit and thermal protection undersuit was used.

Rating: One can provide a subjective overall rating of the dive on a 5-point scale by clicking the appropriate star on the rating scale.

Visibility: Similarly, one can provide a rating of visibility during the dive on a 5-point scale by clicking the appropriate star.

Tags: Tags that describe the type of dive performed may be entered here (separated by commas). Examples of common tags are boat, drift, training, cave etc. Subsurface has many built-in tags. Auto completion is once again offered. For instance, if cav was typed, then the tags cave and cavern are shown for the user to choose from.

Notes: Any additional information can be typed here.

The Save and Cancel buttons are used to save all the information for tabs in the info panel and in the dive profile panel, so there’s no need to use them until ALL other information has been added. Here is an example of a completed Dive Notes panel:

3.1.2. Equipment

The Equipment tab allows the user to enter information about the type of cylinder and gas used, as well as the weights used for a dive. The message in a blue box at the top of the panel:

indicates that the dive is being edited. This is a highly interactive part of Subsurface and the information on cylinders and gases (entered here) affects the behaviour of the dive profile (top right-hand panel).

Cylinders: The cylinder information is entered through a dialogue that looks like this:

The + button at the top right allows the user to add more cylinders for this dive. The dark dustbin icon on the left allows one to delete information for a particular cylinder.

Start by selecting a cylinder type on the left-hand side of the table. To select a cylinder, click in the Type box. This brings up a button that can be used to display a dropdown list of cylinders:

FIGURE:The cylinder drop-down list button

The drop-down list can be used to select the cylinder type used for the dive or the user may start typing in the box which shows the available options for the entered characters. The Size of the cylinder as well as its working pressure (WorkPress) will automatically be shown in the dialogue. If a cylinder is not shown in the dropdown list, type the name and description of that cylinder into the Type field.

Next, indicate the starting pressure and the ending pressure of the gas used during the dive. The unit of pressure (metric/imperial) corresponds to the setting in the Preferences.

Finally, type in the gas mixture used in the O2% field. If air was used, a value of 21% can be entered on this field, or it might be left blank. If nitrox or trimix were used, their percentages of oxygen and/or helium must be specified. Any inappropriate fields should be left empty. After typing the information for the cylinder, press ENTER on the keyboard or click outside the cell that contains the cursor. Information for any additional cylinders can be added by using the + button at the top right hand. Following is an example of a complete description for a dive made using two cylinders (air and EAN50):

FIGURE: a completed cylinder dive information table

Weights: Information about the weight system used during a dive can be entered using a dialogue very similar to that for the cylinder information. If the user clicks the + button on the top right of the weights dialogue, the table looks like this:

If one then clicks on the Type field, a drop-down list becomes accessible through a down-arrow:

FIGURE: Weights type drop-down list button

The drop-down list can then be used to select the type of weight system or the user may start typing in the box which shows the available options for the entered characters. In the Weight field, the weight used during the dive must be typed. After typing the information for the weight system the user must either press ENTER on the keyboard or click outside the cell that contains the cursor. It is possible to enter information for more than one weight system by adding an additional system using the + button on the top right hand. Weight systems can be deleted using the dustbin icon on the left hand. Here is an example of information for a dive with two types of weights: integrated and a weight belt:

FIGURE: A completed weights information table

There’s NO need to click the Save button before the dive profile has been completed.

3.1.3. Creating a Dive Profile

The Dive Profile (a graphical representation of the depth of the dive as a function of time) is indicated in the panel on the top right hand of the Subsurface window. When a dive is manually added to a logbook, Subsurface presents a default dive profile that needs to be modified to best represent the dive being described:

Modifying the dive profile: When the cursor is moved around the dive profile, its position is indicated by two coloured lines (red and green) as shown below. The depth and time that the cursor represents are indicated at the top of the black information box (@ and D). The units (metric/imperial) on the axes are determined by the Preference settings. The dive profile itself comprises several line segments demarcated by waypoints (white dots on the profile, as shown above). The default dive depth is 15 m. If the dive depth was 21 m then the user needs to drag the appropriate waypoints downwards to represent 21 m. To add a waypoint, double-click on any line segment. To move an additional waypoint, drag it. To remove this waypoint, right-click on it and choose "Remove this point" from the context menu. The user needs to drag the waypoints to represent an accurate time duration for the dive. Below is a dive profile that represents a dive to 21 m for 31 min, followed by a 5 minute safety stop at 5 m.

Specifying the gas composition: The gas composition used is clearly indicated along the line segments of the dive profile. This defaults to the first gas mixture specified in the Equipment tab, which was air in the case of the profile illustrated above. The gas mixtures of segments of the dive profile can be edited. This is done by right-clicking on the particular waypoint and selecting the appropriate gas from the context menu. Changing the gas for a waypoint affects the gas shown in the segment to the left of that waypoint. Note that only the gases defined in the Equipment tab appear in the context menu.

Below is the profile of a dive to 20 m for 30 min and with a switch from air to EAN50 at the end of the duration at 20m. In this case the first cylinder in the Equipment tab contained air and the second cylinder contained EAN50.

3.1.4. Saving the hand-entered dive information

The information entered in the Dive Notes tab, the Equipment tab as well as the Dive Profile can now be saved in the user’s logbook by using the two buttons on the top right hand of the Dive Notes tab. If the Save button is clicked, the dive data are saved in the current logbook. If the Cancel button is clicked, the newly entered dive data are discarded. When exiting Subsurface, the user will be prompted once more to save the logbook with the new dive(s).

3.2. Importing new dive information from a Dive Computer

3.2.1. Connecting and importing data from a dive computer.

The use of dive computers allows the collection of a large amount of information about each dive, e.g. a detailed record of depth, duration, rates of ascent/descent and of gas partial pressures. Subsurface can capture this information and present it as part of the dive information, using dive information from a wide range of dive computers. The latest list of supported dive computers can be found at: Supported dive computers.

Several dive computers consume more power when they are in their PC-Communication mode. This could drain the dive computer’s battery. We therefore recommend that the user checks if the dive computer is charged when connected to the USB port of a PC. For example, several Suunto and Mares dive computers do not recharge through the USB connection. Users should refer to the dive computer’s manual if they are unsure whether the dive computer recharges its batteries while connected to the USB port.

To import dive information from a dive computer to a computer with Subsurface, it is necessary that the two pieces of equipment communicate with one another. This involves setting up the communications port (or mount point) of the computer with Subsurface that communicates with the dive computer. In order to set up this communication, one needs to find the appropriate information to instruct Subsurface where and how to import the dive information. Appendix A provides the technical information to help the user achieving this for different operating systems and Appendix B has dive computer specific information.

After this, the dive computer can be hooked up to the user’s PC, which can be achieved by following these steps:

The interface cable should be connected to a free USB port (or the Infra-red or Bluetooth connection set up as described later in this manual)
The dive computer should be placed into PC Communication mode. (Users should refer to the manual of their specific dive computer)
In Subsurface, from the Main Menu, the user must select Import → Import From Dive Computer. Dialogue A in the figure below appears:

Dive computers tend to keep a certain number of dives in their memory, even though these dives have already been imported to Subsurface. For that reason Subsurface only imports dives that have not been uploaded before. This makes the download process faster on most dive computers and also saves battery power of the dive computer (at least for those not charging while connected via USB). If, for some reason, the user wishes to import ALL dives from the dive computer, even though some may already be in the logbook, then check the check box labelled Force download of all dives.

The dialogue has two drop-down lists, Vendor and Dive Computer. On the vendor drop-down list select the make of the computer, e.g. Suunto, Oceanic, Uwatec, Mares. On the Dive Computer drop-down list, the model name of the dive computer must be selected, e.g. D4 (Suunto), Veo200 (Oceanic), or Puck (Mares).
The Device or Mount Point drop-down list contains the USB or Bluetooth port name that Subsurface needs in order to communicate with the dive computer. The appropriate port name must be selected. Consult Appendix A and Appendix B for technical details on how to find the appropriate port information for a particular dive computer and, in some cases, how to do the correct settings to the operating system of the computer on which Subsurface is running.
If all the dives on the dive computer need to be downloaded, check the checkbox Force download of all dives. Normally, Subsurface only downloads dives after the date-time of the last dive in the Dive List panel. If one or more of your dives in Subsurface have been accidentally deleted or if there are older dives that still need to be downloaded from the dive computer, this checkbox needs to be activated. Some dive computers (e.g. Mares Puck) do not provide a contents list to Subsurface before the download in order to select only new dives. Consequently, for these dive computers, all dives are downloaded irrespective of the status of this check box.
If the checkbox Always prefer downloaded dives has been checked and, during download, dives with identical date-times exist on the dive computer and on the Subsurface Dive List panel, the record in the Subsurface divelog will be overwritten by the record from the dive computer
Do not check the checkboxes labelled Save libdivecomputer logfile and Save libdivecomputer dumpfile. These are only used as diagnostic tools when problems with downloads are experienced (see below).
The OK button must then be clicked. Dialogue B in the figure above appears.
With communication established, one can see how the data are retrieved from the dive computer. Depending on the make of the dive computer and/or number of recorded dives, this could take some time. The user should be patient. The Download dialogue shows a progress bar at the bottom of the dialogue (for some dive computers the progress information could be inaccurate as we cannot determine how much downloadable data there is until all data have been downloaded). When the download of the dive information is complete, all the imported dives appear in the Dive List, sorted by date and time. Disconnect and switch off the dive computer to conserve its battery power. If a particular dive is selected, the Dive Profile panel shows an informative graph of dive depth against time for that particular dive.
If there is a problem in communicating with the dive computer, an error message will be shown, similar to this text: "Unable to open /dev/ttyUSB0 Mares (Puck Pro)". Refer to the text in the box below.

PROBLEMS WITH DATA DOWNLOAD FROM A DIVE COMPUTER?

Check the following:

Is the dive computer still in PC-communication or Upload mode?
Is the battery of the dive computer fully charged? If not then the battery must be charged or replaced.
Is the connecting cable faulty? Does the cable work perfectly using other software? Has it worked before, or is this the first time the cable is being used?
Consult Appendix A and make sure that the correct Mount Point was specified (see above).
On Unix-like operating systems, does the user have write permission to the USB port? If not, consult Appendix A

If the Subsurface computer does not recognise the USB adaptor by showing an appropriate device name next to the Mount Point, then there is a possibility that the cable or USB adaptor is faulty. A faulty cable is the most common cause of communication failure between dive computer and Subsurface computer. It is also possible that the Subsurface computer cannot interpret the data. Perform a download for diagnostic purposes with the following two check boxes checked in the download dialogue discussed above:

Save libdivecomputer logfile
Save libdivecomputer dumpfile

Important: These check boxes are only used when problems are encountered during the download process: under normal circumstances they should not be checked. When checking these boxes, the user is prompted to select a folder to save the information to. The default folder is the one in which the Subsurface dive log is kept.

Important: After downloading with the above checkboxes checked, no dives are added to the Dive List but two files are created in the folder selected above:

subsurface.log
subsurface.bin

These files should be send to the Subsurface mail list: subsurface@hohndel.org with a request for the files to be analysed. Provide the dive computer make and model as well as contextual information about the dives recorded on the dive computer.

3.2.2. Changing the name of a dive computer

It may be necessary to distinguish between different dive computers used to upload dive logs to Subsurface. For instance if one’s partner’s dive computer is the same make and model as one’s own and dive logs are uploaded from both dive computers to the same Subsurface computer, then one would perhaps like to call one dc "Alice’s Suunto D4" and the other one "Bob’s Suunto D4". Alternatively, perhaps a technical diver dives with two or more dive computers of the same model, the logs of both (or all) being uploaded. In this case it might be prudent to call one of them "Suunto D4 (1)" and another one "Suunto D4 (2)". This is easily done in Subsurface. On the Main Menu, select Log → Edit device names. A dialog opens, indicating the current Model, ID and Nickname of the dive computers used for upload. Edit the Nickname field for the appropriate dive computer. After saving the Nickname, the dive logs show the nickname for that particular device instead of the model name, allowing easy identification of devices.

3.2.3. Updating the dive information imported from the dive computer.

The information from the dive computer is not complete and more details must be added in order to have a fuller record of the dives. To do this, the Dive Notes and the Equipment tabs on the top left hand of the Subsurface window should be used.

3.2.4. Dive Notes

The date and time of the dive, gas mixture and (often) water temperature is shown as obtained from the dive computer, but the user needs to add some additional information by hand in order to have a more complete dive record. If the contents of this tab is changed or edited in any way, the message in a blue box at the top of the panel indicates that the dive is being edited. If the user clicks on the Dive Notes tab, the following fields are visible:

The Time field reflects the date and time of the dive. By clicking the date, a calendar is displayed from which one can choose the correct date. Press ESC to close the calendar. The time values (hour and minutes) can also be edited directly by clicking on each of them in the text box and by overtyping the information displayed.

Air/water temperatures: Air and water temperatures during the dive are shown in these fields to the right of the Start time. Many dive computers supply water temperature information and this field may therefore not require further editing. If editing is required, only a value is required, the units of temperature will be automatically supplied by Subsurface (according to the Preferences, metric or imperial units will be used).

Location: In this field one should type in text that describes the site where the dive was performed, e.g. "Tihany, Lake Balaton, Hungary". Auto completion of location names will make this easier when a user frequently dives at the same sites.

Coordinates: The geographic coordinates of the dive site should be entered here. These can come from three sources:

The user can find the coordinates on the world map in the bottom right hand part of the Subsurface window. The map displays a green bar indicating "Move the map and double-click to set the dive location". Double-click at the appropriate place, the green bar disappears and the coordinates are stored.
The user can obtain the coordinates from the Subsurface Companion app if an Android device with GPS was used and the if the coordinates of the dive site were stored using that device. Click here for more information

The coordinates can be entered by hand if they are known, using one of four formats with latitude followed by longitude:

ISO 6709 Annex D format e.g. 30°13'28.9"N 30°49'1.5"E
Degrees and decimal minutes, e.g. N30° 13.49760' , E30° 49.30788'
Degrees minutes seconds, e.g. N30° 13' 29.8" , E30° 49' 1.5"
Decimal degrees, e.g. 30.22496 , 30.821798

Southern hemisphere latitudes are given with a S, e.g. S30°, or with a negative value, e.g. -30.22496. Similarly, western longitudes are given with a W, e.g. W07°, or with a negative value, e.g. -7.34323.

Divemaster: The name of the dive master or dive guide for this dive should be entered in this field which offers auto completion based on the list of dive masters in the current logbook.

Buddy: In this field, one enters the name(s) of the buddy / buddies (separated with commas) who accompanied him/her on the dive. Auto completion based on the list of buddies in the current logbook is offered.

Suit: Here the type of diving suit used for the dive can be entered. Auto completion of the suit description is available. Some dry-suit users may choose to use this field to record what combination of suit and thermal protection undersuit was used.

Rating: One can provide a subjective overall rating of the dive on a 5-point scale by clicking the appropriate star on the rating scale.

Visibility: Similarly, one can provide a rating of visibility during the dive on a 5-point scale by clicking the appropriate star.

Tags: Tags that describe the type of dive performed can be entered here (separated by commas). Examples of common tags are boat, drift, training, cave, etc. Subsurface has many built-in tags. If the user starts typing a tag, the program will list the tags that correspond to the typing. For instance, if the user typed cav, then the tags cave and cavern are shown for the user to choose from.

Notes: Any additional information for the dive can be entered here.

3.2.5. Equipment

The Equipment tab allows one to enter information about the type of cylinder and gas used as well as the weights used for the dive. The message in a blue box at the top of the panel:

indicates that the dive is being edited. This is a highly interactive part of Subsurface and the information on cylinders and gases (entered here) determines the behaviour of the dive profile (top right-hand panel).

Cylinders: The cylinder information is entered through a dialogue that looks like this:

In most cases Subsurface obtains the gas used from the dive computer and automatically inserts the gas composition(% oxygen) in the table. The + button at the top right allows the user to add more cylinders for this dive. The dark dustbin icon on the left allows the deletion of information for a cylinder.

The user should start by selecting a cylinder type on the left-hand side of the table. To select a cylinder, the cylinder type box should be clicked. This brings up a list button that can be used to display a dropdown list of cylinders:

The drop-down list can then be used to select the cylinder type that was used for this dive or the user may start typing in the box which shows the available options for the entered characters. The Size of the cylinder as well as its working pressure (WorkPress) will automatically be shown in the dialogue.

Next one must indicate the starting pressure and the ending pressure of the specified gas during the dive. The unit of pressure (metric/imperial) corresponds to the settings chosen in the Preferences.

Finally, the user must provide the gas mixture used. If air was used, the value of 21% can be entered or this field can be left blank. If nitrox or trimix were used, their percentages of oxygen and/or helium should be entered. Any inappropriate fields should be left empty. After typing the information for the cylinder, either press ENTER on the keyboard or click outside the cell that contains the cursor. Information for any additional cylinders can be added by using the
button at the top right hand. Following is an example of a complete description for a dive using two cylinders (air and EAN50):

Weights: Information about the weight system used can be entered using a dialogue very similar to that of the cylinder information. If one clicks the + button on the top right of the weights dialogue, the table looks like this:

By clicking on the Type field, a drop-down list becomes accessible through a down-arrow:

The drop-down list can then be used to select the type of weight system used during the dive or the user may start typing in the box which shows the available options for the entered characters. In the Weight field, type in the amount of weight used during the dive. After specifying the weight system, the user can either press ENTER on the keyboard or click outside the cell with the cursor. It is possible to enter information for more than one weight system by adding an additional system using the + button on the top right hand. Weight systems can be deleted using the dustbin icon on the left hand. Here is an example of information for a dive with two types of weights: integrated as well as a weight belt:

3.2.6. Adding Bookmarks to a dive

Many divers wish to annotate their dives with text that indicate particular events during the dive, e.g. "Saw dolphins", or "Released surface bouy". This is easily done:

Right-click at the appropriate point on the dive profile. This brings up the dive profile context menu. Select Add bookmark. A red flag is placed on the dive profile at the point that was initially selected (see A below).
Right-click on the red flag. This brings up the context menu (see B below). Select Edit name.
A text box is shown. Type the explanatory text for the bookmark (see C below). Select OK. This saves the text associated with the bookmark.
If one hovers using the mouse over the red bookmark, the appropriate text is shown at the bottom of the information box (see D below).

3.2.7. Saving the updated dive information

The information entered in the Dive Notes tab and the Equipment tab can be saved by using the two buttons on the top right hand of the Dive Notes tab. If the Save button is clicked, the dive data are saved. If the Cancel button is clicked, then the newly entered dive data are deleted, although the dive profile obtained from the dive computer will be retained. When the user exits Subsurface there is a final prompt to confirm that the new data should be saved.

3.3. Importing dive information from other digital data sources or other data formats

If a user has been diving for some time, it is possible that several dives were logged using other dive log software. This information does not need retyping because these dive logs can probably be imported into Subsurface. Subsurface will import dive logs from a range of other dive log software. While some software is supported natively, for others the user has to export the logbook(s) to an intermediate format so that they can then be imported by Subsurface. Currently, Subsurface supports importing CSV log files from several sources. APD LogViewer, XP5 and Sensus files are preconfigured, but because the import is flexible, users can configure their own imports. Manually kept log files (e.g. in spreadsheet) can also be imported by configuring the CSV import. Subsurface can also import UDDF and UDCF files used by some divelog software and some dive computers, like the Heinrichs & Weikamp DR5. Finally, for some divelog software like Mares Dive Organiser it is currently suggested to import the logbooks first into a webservice like divelogs.de and then import them from there with Subsurface, as divelogs.de supports a few additional logbook formats that Subsurface currently cannot parse.

When importing dives, Subsurface tries to detect multiple records for the same dive and merges the information as best as it can. If there are no time zone issues (or other reasons that would cause the beginning time of the dives to be significantly different) Subsurface will not create duplicate entries.

3.3.1. Using the universal import dialogue

Importing dives from other software is performed through a universal interface that is activated by selecting Import from the Main Menu, then clicking on Import Log Files. This brings up the dialogue A below.

Towards the bottom right is a dropdown selector with a default label of Dive Log Files which gives access to the different types of direct imports available, as in dialogue B, above. Currently these are:

XML-formatted dive logs (Divinglog 5.0, MacDive and several other dive log systems)
UDDF-formatted dive logs (e.g. Kenozoooid)
UDCF-formatted dive logs
JDiveLog
Suunto Dive Manager (DM3 and DM4)
CSV (text-based and spreadsheet-based) dive logs.

Selecting the appropriate file in the file list of the dialogue opens the imported dive log in the Subsurface Dive List. Some other formats, not accessible through the Import dialogue are also supported, as explained below.

3.3.2. Importing from Mares Dive Organiser V2.1

Since Mares utilise proprietary Windows software not compatible with multi-platform applications, these dive logs cannot be directly imported into Subsurface. Mares dive logs need to be imported using a three-step process, using www.divelogs.de as a mechanism to extract the dive log information.

The dive log data from Mares Dive Organiser need to be exported to the user’s desktop, using a .sdf file name extension. Refer to Appendix C for more information.
Data should then be imported into www.divelogs.de. One needs to create a user account in www.divelogs.de, log into that web site, then select Import Logbook → Dive Organiser from the menu on the left hand side. The instructions must be carefully followed to transfer the dive information (in .sdf format) from the Dive Organiser data base to www.divelogs.de.
Finally, import the dives from divelogs.de to Subsurface, using the instructions below.

3.3.3. Importing dives from divelogs.de

The import of dive information from divelogs.de is simple, using a single dialogue box. The Import→Import form Divelogs.de option should be selected from the Main Menu. This brings up a dialogue box (see figure on left [A] below). Enter a user-ID and password for divelogs.de into the appropriate fields and then select the Download button. Download from divelogs.de starts immediately, displaying a progress bar in the dialogue box. At the end of the download, the success status is indicated (see figure on the right [B], below). The Apply button should then be selected, after which the imported dives appear in the Subsurface Dive List panel.

3.3.4. Importing dives in CSV format

Sometimes dive computers export dive information as files with comma-separated values (.CSV). For example, the APD Inspiration and Evolution closed circuit rebreather (CCR) systems export dive information in a CSV formatted file that normally contains information for a single dive only. These files can easily be imported into Subsurface. CSV files are normally organised into a single line that provides the headers of the data columns, followed by the data, one record per line. CSV files can be opened with a normal text editor. Following is a highly simplified and shortened example of a CSV file from an APD rebreather:

        Dive Time (s)   Depth (m)       pO₂ - Setpoint (Bar)  pO₂ - C1 Cell
1 (Bar) Ambient temp. (Celsius)
        0       0.0     0.70    0.81    13.1
        0       1.2     0.70    0.71    13.1
        0       0.0     0.70    0.71    13.1
        0       1.2     0.70    0.71    13.2
        0       1.2     0.70    0.71    13.1
        10      1.6     0.70    0.72    12.7
        20      1.6     0.70    0.71    12.6
        30      1.7     0.70    0.71    12.6
        40      1.8     0.70    0.68    12.5
        50      1.6     0.70    0.68    12.5
        60      2.4     0.70    0.69    12.5
        70      3.5     0.70    0.69    12.4
        80      4.2     0.70    0.72    12.5
        90      4.0     0.70    0.71    12.4

Note that each title may comprise more than one word; for instance Dive Time (s) in the above data example. Before being able to import the data to Subsurface one first needs to know:

Which character separates the different columns within a single line of data? This field separator should be either a comma (,) or a TAB character. This can be determined by opening the file with a text editor. If it is comma-delimited, then the comma characters between the values are clearly visible. If no commas are evident and the numbers are aligned in columns, the file is probably TAB-delimited (i.e. it uses a TAB as a field separator, as in the above example).
Which data columns need to be imported into Subsurface? The Dive Time and Depth columns are always required. Open the file using a text editor and note the titles of the columns to be imported and their column positions. For instance for the above example:
```
Time:           column 1
Depth:          column 2
Temperature:    column 5
pO₂:          column 4
```

Armed with this information, importing the data into Subsurface is straightforward. Select Import→Import Log Files from the main menu. In the resulting file selection menu, select CSV files, after which a common configuration dialog appears for all the files with a CSV extension:

There are pre-configured definitions for some dive computers, e.g. the APD rebreathers. If the user’s dive computer is on this list, it should be selected using the dropdown box labeled Pre-configured imports. Select the button at the bottom right to indicate whether the dive data are in metric of imperial units. Finally OK should be clicked and the dive will be imported and listed in the Dive List tab of Subsurface.

If the dive computer is not on the pre-configured list, the user must select the Field Separator (TAB or comma) for the particular CSV file, using the appropriate dropdown list. and indicate which columns in the CSV file contain which data variables. For each data column used for import, the user must check the appropriate check box and indicate in which column these data are found. For instance, the image above corresponds to the dialogue that would apply to the CSV data set described above the image. After completing the column specification, select the OK button and the dive will be imported and listed in the Dive List tab of Subsurface.

3.3.5. Importing dives from manually kept CSV file

If one keeps dive logs in a spreadsheet, there is an option to import those dives as well. Spreadsheet data, exported as a CSV file, can be imported to Subsurface. When importing manually kept log files, the information needed is quite different as we are importing only metadata, not profile samples.

Similarly to importing dives in CSV format (see above), one needs to know the internal format of the CSV data to import.

Which character separates the different columns within a single line of data? This should be either a comma (,), semicolon (;) or a TAB character, and could be determined by opening the file with a text editor. If it is comma-delimited, then the comma characters between the values are clearly visible. If no commas are evident and the data are in clear columns, the file is probably TAB-delimited (i.e. it uses a TAB as a field separator, as in the above example). A recommended field separator for the export is tab, as commas might be part of the field values themselves. Therefore the use of an appropriate field separator in very important.
Which columns need to be imported into Subsurface? We do not currently have any mandatory input fields, but some, e.g. dive duration are crucial for the log file to make any sense. Possible options can be seen in the image below and one should include all the fields available in both your log file and in the Subsurface import.
Units used for depth, weight and temperature. We consider depth to be either feet or meters, weight kilograms or pounds and temperature either Celsius or Fahrenheit. However, the users can select Metric or Imperial in the Preferences tab of Subsurface. No mixture of unit systems is allowed for the different fields.

Importing manually kept CSV log files is quite straight forward, but there might be many fields and counting the field numbers is error prone. Therefore validation of the data to be imported is critical.

To import the dives, select Import→Import Log Files from the menu bar. If the CSV option in the dropdown list is selected and the file list includes file names ending with .CSV, one can select the Manual dives tab that will bring up the following configuration dialog:

FIGURE: Download dialog for Manual CSV logs

The input fields can be configured as appropriate, and when everything is done the OK button should be selected to perform the import. New dives should appear in the Dive List area of Subsurface.

3.4. Importing GPS coordinates with the Subsurface Companion App for mobile phones

Using the Subsurface Companion App on an Android device with a GPS, the coordinates for the diving location can be automatically passed to the Subsurface dive log. The Companion App stores the dive locations on a dedicated Internet-based file server. Subsurface, in turn, can collect the localities from the file server.

To do this:

3.4.1. Create a Companion App account

Register on the Subsurface companion web page. A confirmation email with instructions and a personal DIVERID will be sent, a long number that gives access to the file server and Companion App capabilities.
Download the app from Google Play Store or from F-Droid.

3.4.2. Using the Subsurface companion app on a smartphone

On first use the app has three options:

Create a new account. Equivalent to registering in Subsurface companion page using an Internet browser. One can request a DIVERID using this option, but this is supplied via email and followed up by interaction with the Subsurface companion web page in order to activate the account.
Retrieve an account. If users forgot their DIVERID they will receive an email to recover the number.
Use an existing account. Users are prompted for their DIVERID. The app saves this DIVERID and does not ask for it again unless one uses the Disconnect menu option (see below).

In the Subsurface main program, the DIVERID should also be entered on the Default Preferences panel, obtained by selecting File→Preferences→Defaults from the main menu in Subsurface itself. This facilitates synchronisation between Subsurface and the Companion App.

Creating new dive locations

Now one is ready to get a dive position and send it to the server. The Android display will look like the left hand image (A) below, but without any dives.

Touch the "+" icon on the top right to add a new dive site, a menu will be showed with 3 options:

Current: A prompt for a place name (or a request to activate the GPS if it is turned off) will be displayed, after which the current location is saved.
Use Map: This option allows the user to fix a position by searching a world map. A world map is shown (see B below) on which one should indicate the desired position with a long press on the touch sensitive screen (if the marked location is erroneous, simply indicate a new location) and select the check symbol in the upper right. A dialog is shown allowing to enter the name of the dive location and the date-time of the dive (see C below). In order to import this dive location in Subsurface it’s advisable to set the time to agree with the time of that dive on the dive computer.

FIGURE: Companion App, add location using map

Import local GPX file: The android device searches for .gpx files and located archives will be shown. The selected .gpx file is opened and the stored locations shown. Now one needs to select the appropriate locations, then select the tab in the upper right, after which the locations will be sent to the web service and added to the list on the Android device.

Dive lists of dive locations

The main screen shows a list of dive locations, each with a name, date and time (see A below). Some locations may have an arrow-up icon over the selection box to the left indicating that they require upload to the server. One can select individual dive locations from the list. A selected location has a check mark in the selection box on the left. Group operations (such as Delete or Send) are performed on several locations that are selected.

Dive locations in this list can be viewed in two ways: a list of locations or a map indicating the dive locations. The display mode (List or Map) is changed by selecting Dives at the top left of the screen (see A below) and then selecting the display mode. The display mode can be changed either from the list of locations or from the map (see B below). If one selects a location (on the list or on the map), an editing panel opens (see C below) where the dive description or other details may be changed.

When one clicks on a dive (not selecting the check box), the name given to it, date/time and GPS coordinates will be shown, with two options at the top of the screen:

Edit (pencil): Change the text name or other characteristics of the dive location.
Maps: Display a map showing the dive location.

After editing and saving a dive location (see C above), one needs to upload it to the web service, as explained below.

Uploading dive locations

There are several ways to send locations to the server. The easiest is by simply selecting the locations (See A below) and then touching the right arrow at the top right of the screen.

Users must be careful, as the trash icon on the right means exactly what it should; it deletes the selected dive location(s).

FIGURE: Screen shots (A-B) of companion app

After a dive trip using the Companion App, all dive locations are ready to be downloaded to a Subsurface dive log (see below).

Settings on the Companion app

Selecting the Settings menu option results in the right hand image above (B).

Server and account

Web-service URL. This is predefined (http://api.hohndel.org/)
User ID. The DIVERID obtained by registering as described above. The easiest way to obtain it is simply to copy and paste from the confirmation email but, of course, users can also type this information.

Synchronisation

Synchronize on startup. If selected, dive locations in the Android device and those on the web service synchronise each time the app is started.
Upload new dives. If selected, each time the user adds a dive location it is automatically sent to the server.

Background service

Instead of entering a unique dive location, users can leave the service running in the background of their Android device, allowing the continuous collection of GPS locations.

The settings below define the behaviour of the service:

Min duration. In minutes. The app will try to get a location every X minutes until stopped by the user.
Min distance. In meters. Minimum distance between two locations.
Name template. The name the app will use when saving the locations.

How does the background service work? Assuming the user sets 5 minutes and 50 meters in the settings above, the app will start by recording a location at the current location, followed by another one at every 5 minutes or every time one moves 50m from previous location. If subsequent locations are within a radius of 50 meters from the previous one, a new location is not saved. If the user is not moving, only one location is saved, but if the user is moving, a trace of the route is obtained by saving a location every 50 meters.

Other

Mailing List. The mail box for Subsurface. Users can send an email to the Subsurface mailing list.
Subsurface website. A link to the URL of Subsurface web
Version. Displays the current version of the Companion App.

Search

Search the saved dive locations by name or by date and time.

Start service

Initiates the background service following the previously defined settings.

Disconnect

This is a badly named option that disconnects the app from the server by resetting the user ID in the app, showing the first screen where an account can be created, retrieve the ID for an existing account or use the users own ID. The disconnect option is useful if a user’s Android device was used to download the dive locations of another registered diver.

Send all locations

This option sends all locations stored in the Android device to the server.

3.4.3. Downloading dive locations to the Subsurface divelog

Download dive(s) from a dive computer or enter them manually into Subsurface before obtaining the GPS coordinates from the server. The download dialog can be reached via Ctrl+G or from the Subsurface Main Menu Import → Import GPS data from Subsurface Service, resulting in the image on the left (A), below. On first use the DIVERID text box is blank. Provide a DIVERID, then select the Download button to initiate the download process, after which the screen on the right (B) below appears:

FIGURE: Downloading Companion app GPS data

Note that the Apply button is now active. By clicking on it, users can update the locations of the newly entered or uploaded dives in Subsurface which applies the coordinates and names entered on the app for all the new dives that match the date-times of the uploaded GPS localities. If one has entered the name of the dive location in Subsurface before downloading the GPS coordinates, this name will take precedence over downloaded one.

Since Subsurface matches GPS locations from the Android device and dive information from the dive computer based on date-time data, automatic assignment of GPS data to dives is dependent on agreement of the date-time information between these two devices. Although Subsurface has a wide range tolerance, it may be unable to identify the appropriate dive if there is a large difference between the time in the dive computer and that of the Android device, resulting in no updates.

Similar date-times may not always be possible and there may be many reasons for this (e.g. time zones), or Subsurface may be unable to decide which is the correct position for a dive (e.g. on repetitive dives while running background service there may be several locations that would be included in the time range that fit not only the first dive, but one or more subsequent dives as well). A workaround for this situation to manually edit the date-time of a dive in the Subsurface Dive List before downloading the GPS data and then to change the date-time back again after downloading GPS data.

TIPS:

Background service, being a very powerful tool, may fill the location list with many unnecessary locations not corresponding to the exact dive point but reflecting the boat’s route. Currently these locations are difficult to delete from the server. In some situations it is therefore prudent to clean up the list on the Android device before sending the dive points to the web server by simply deleting the inappropriate locations. This might be necessary, for instance, if one wants to keep the location list clear to see dives in the web service map display (see above).
It may also make sense to give informative names to the locations sent to the web server, or at least to use an informative name in the Name Template setting while running the background service, especially on a dive trip with many dives and dive locations.

3.5. Adding photographs to dives

Many (if not most) divers take a camera with them and take photographs during a dive. One would like to associate each photograph with a specific dive. Subsurface allows one to load photos into a dive. Photos are superimposed on the dive profile, from where they can be viewed.

3.5.1. Loading photos and getting synchronisation between dive computer and camera

Left-lick on a dive or on a group of dives on the dive list. Then right-click on this dive or group of dives and choose the option Load Images:

The system file browser appears. Select the folder and photographs that need to be loaded into Subsurface and click the Open button.

This brings one to the time synchronisation dialog, shown below. The critical problem is that the time synchronisation is not perfect between the dive computer used during a dive, and the camera used during that same dive. These two devices often differ by several minutes. If Subsurface can achieve synchronisation, then the exact times of photographs can be used to position photographs on the dive profile.

Subsurface achieves this synchronisation in two ways:

Manually: If the user wrote down the exact camera time at the start of a dive, the difference in time between the two devices can be determined. Actually, as long as the device settings for time has not been changed in either device, one could write down the times of both devices after the dive or even at the end of the day. One can then manually set the time difference in the Time shift dialog. Towards the top of the dialog is a time setting tool immediately under the heading Shift times of image(s) by, evident in figure A below. If the camera time is 7 minutes later than that of the dive computer, set the time setting tool to a value of 00:07. Select either the earlier or later radio button. In the above example, the earlier option is appropriate, since the photos need to be shifted 7 minutes earlier (camera is 7 minutes ahead of dive computer). Ignore any "AM" or "PM" suffix in that tool. Click the OK button and synchronisation is achieved.

By photograph: There is a very slick way of achieving synchronisation. If one takes a photograph of the face of the dive computer showing the time, then Subsurface can obtain the exact time the photograph was taken, using the metadata that the camera stores within each photo. In order to do this, use the bottom half of the Time shift_ dialog. If one uses the bottom part, the top part of the dialog is ignored. Click on the horizontal bar entitled "Select image of divecomputer showing time. This brings up a file browser with which one can select the photograph of the dive computer. Select the photograph using the file browser and click on OK. This photograph of the dive computer appears in the bottom panel of the Shift times dialog. Now Subsurface knows exactly when the photograph has been taken. Now set the date-time dialog to the left of the photo so that this tool reflects the date and time of the dive computer in the photo. When the date-time tool has been set, Subsurface knows exactly what the time difference between camera and dive computer is, and synchronisation is achieved. There is a photograph with the face of the dive computer and with the date-time tool set to the date-time on image B above.

If the timestamp of a photograph is long before or after the dive, it is not placed on the dive profile. If the timestamp of the photo is within 30 minutes of the dive, it is shown.

3.5.2. Viewing the photos

In order to view the photos added to a dive, activate the show-photos button in the tool bar to the left of the dive profile:

After the images have been loaded, they also appear in the Photos tab of the Dive Notes panel. They also appear as tiny icons on the dive profile at the appropriate positions reflecting the time each photograph was taken. See below:

If one hovers with the mouse over any of the photo icons, then a thumbnail photo is shown of the appropriate photo. See the image below:

If one clicks on the thumbnail, then a full size photo is shown overlaid onto the Subsurface window. This allows good viewing of the photographs that have been added. See below:

4. Obtaining more information about dives entered into the logbook

4.1. The Dive Info tab (for individual dives)

The Dive Info tab gives some summary information about a particular dive that has been selected in the Dive List. Useful information here includes the surface interval before the dive, the maximum and mean depths of the dive, the gas volume consumed, the surface air consumption (SAC) and the number of oxygen toxicity units (OTU) incurred.

Gas consumption and SAC calculations: Subsurface calculates SAC and Gas consumption taking in account gas incompressibility, particularly at tank pressures above 200 bar, making them more accurate. Users should refer to Appendix D for more information.

4.2. The Stats tab (for groups of dives)

The Stats tab gives summary statistics for more than one dive, assuming that more than one dive has been selected in the Dive List using the standard Ctrl-click or Shift-click of the mouse. If only one dive has been selected, figures pertaining to only that dive are given. This tab shows the number of dives selected, the total amount of dive time in these dives, as well as the minimum, maximum and mean for the dive duration, water temperature and surface air consumption (SAC). It also shows the depth of the shallowest and deepest dives of those selected.

4.3. The Dive Profile

Of all the panels in Subsurface, the Dive Profile contains the most detailed information about each dive. The Dive Profile has a button bar on the left hand side that allows control over several display options. The functions of these buttons are described below. The main item in the Dive Profile is the graph of dive depth as a function of time. In addition to the obvious information of the depth it also shows the ascent and descent rates compared to the recommended speed of going up or down in the water column. This information is given using different colours:

Colour	Descent speed (m/min)	Ascent speed (m/min)
Red	> 30	> 18
Orange	18 - 30	9 - 18
Yellow	9 - 18	4 - 9
Light green	1.5 - 9	1.5 - 4
Dark green	< 1.5	< 1.5

The profile also includes depth readings for the peaks and troughs in the graph. Thus, users should see the depth of the deepest point and other peaks. Mean depth is marked with a horizontal red line.

In some cases the dive profile does not fill the whole area of the Dive Profile panel. Clicking the Scale button in the toolbar on the left of the dive profile frequently increases the size of the dive profile to fill the area of the panel efficiently.

Water temperature is displayed with its own blue line with temperature values placed adjacent to significant changes.

The dive profile can include graphs of the partial pressures of O2, N2, and He during the dive (see figure above) as well as a calculated and dive computer reported deco ceilings (only visible for deep, long, or repetitive dives). Partial pressures of oxygen are indicated in green, those of nitrogen in black, and those of helium in dark red. These partial pressure graphs are shown below the profile data.

Clicking this button allows display of the partial pressure of oxygen during the dive. This is depicted below the dive depth and water temperature graphs.

Clicking this button allows display of the partial pressure of nitrogen during the dive.

Clicking this button allows display of the partial pressure of helium during the dive. This is only of importance to divers using Trimix, Helitrox or similar breathing gasses.

The air consumption graph displays the tank pressure and its change during the dive. The air consumption takes depth into account so that even when manually entering the start and end pressures the graph is not a straight line. Similarly to the depth graph the slope of the tank pressure gives the user information about the momentary SAC rate (Surface Air Consumption) when using an air integrated dive computer. Here the colour coding is not relative to some absolute values but relative to the average normalised air consumption during the dive. So areas that are red or orange indicate times of increased normalized air consumption while dark green reflects times when the diver was using less gas than average.

Clicking on the heart rate button will allow the display of heart rate information during the dive if the dive computer was attached to a heart rate sensor.

It is possible to zoom into the profile graph. This is done either by using the scroll wheel / scroll gesture of your mouse or trackpad. By default Subsurface always shows a profile area large enough for at least 30 minutes and 30m (100ft) – this way short or shallow dives are intuitively recognizable; something that free divers clearly won’t care about.

Measurements of depth or time differences can be achieved by using the ruler button on the left of the dive profile panel. The measurement is done by dragging the red dots to the two points on the dive profile that the user wishes to measure. Information is then given in the horizontal white area underneath the two red dots.

Photographs that have been added to a dive can be shown on the profile by selecting the Show-photo button. The position of a photo on the profile indicates the exact time when this photo was taken. If this button is not active, the photos are hidden.

The profile can also include the dive computer reported ceiling (more precisely, the deepest deco stop that the dive computer calculated for each particular moment in time) as a red overlay on the dive profile. Ascent ceilings arise when a direct ascent to the surface increases the risk of a diver suffering from decompression sickness (DCS) and it is necessary to either ascend slower or to perform decompression stop(s) before ascending to the surface. Not all dive computers record this information and make it available for download; for example all of the Suunto dive computers fail to make this very useful data available to divelog software. Subsurface also calculates ceilings independently, shown as a green overlay on the dive profile. Because of the differences in algorithms used and amount of data available (and other factors taken into consideration at the time of the calculation) it is unlikely that ceilings from dive computers and from Subsurface are the same, even if the same algorithm and gradient factors (see below) are used. It is also quite common that Subsurface calculates a ceiling for non-decompression dives when the dive computer stayed in non-deco mode during the whole dive (represented by the dark green section in the profile at the beginning of this section). This is caused by the fact that Subsurface’s calculations describe the deco obligation at each moment during a dive, while dive computers usually take the upcoming ascent into account. During the ascent some excess nitrogen (and possibly helium) are already breathed off so even though the diver technically encountered a ceiling at depth, the dive still does not require an explicit deco stop. This feature allows dive computers to offer longer non-stop bottom times.

If the dive computer itself calculates a ceiling and makes it available to Subsurface during upload of dives, this can be shown as a red area by checking Dive computer reported ceiling button on the Profile Panel.

If the Calculated ceiling button on the Profile Panel is clicked, then a ceiling, calculated by Subsurface, is shown in green if it exists for a particular dive (A in figure below). This setting can be modified in two ways:

If, in addition, the show all tissues button on the Profile Panel is clicked, the ceiling is shown for the tissue compartments following the Bühlmann model (B in figure below).

If, in addition, the 3m increments button on the Profile Panel is clicked, then the ceiling is indicated in 3 m increments (C in figure below).

Gradient Factor settings strongly affect the calculated ceilings and their depths. For more information about Gradient factors, see the section on Gradient Factor Preference settings. The currently used gradient factors (e.g. GF 35/75) are shown above the depth profile if the appropriate toolbar buttons are activated. N.B.: The indicated gradient factors are NOT the gradient factors in use by the dive computer, but those used by Subsurface to calculate deco obligations during the dive. For more information external to this manual see:

4.4. The Dive Profile context menu

The context menu for the Dive Profile is accessed by right-clicking while the mouse cursor is over the Dive Profile panel. The menu allows the creation of Bookmarks or Gas Change Event markers other than the ones that might have been imported from a Dive Computer. Markers are placed against the depth profile line and with the time of the event set by where the mouse cursor was when the right mouse button was initially clicked to bring up the menu. Gas Change events open a further selection of which gas is being switched to, the list based on the available gases defined in the Equipment Tab. By right-clicking while over an existing marker, the menu extends adding options to allow deletion of the marker or to allow all markers of that type to be hidden. Hidden events can be restored to view by selecting Unhide all events from the context menu.

4.5. The Information Box

The Information box displays a large range of information pertaining to the dive profile. Normally the Information Box is located to the top left of the Dive Profile panel. If the mouse points outside of the Dive Profile panel, then only the top line of the Information Box is visible (see left-hand part of figure (A) below). The Information Box can be moved around in the Dive Profile panel by click-dragging it with the mouse so that it is not obstructing important detail. The position of the Information Box is saved and used again during subsequent dive analyses.

The moment the mouse points inside the Dive Profile panel, the information box expands and shows many data items. In this situation, the data reflect the time point along the dive profile indicated by the mouse cursor (see right-hand part of figure (B) above where the Information Box reflects the situation at the position of the cursor [arrow] in that image). Therefore, moving the cursor in the horizontal direction allows the Information Box to show information for any point along the dive profile. In this mode, the Information Box gives extensive statistics about depth, gas and ceiling characteristics of the particular dive. These include: Time period into the dive (indicated by a @), depth, cylinder pressure (P), temperature, ascent/descent rate, surface air consumption (SAC), oxygen partial pressure, maximum operating depth, equivalent air depth (EAD), equivalent narcotic depth (END), equivalent air density depth (EADD), decompression requirements at that instant in time (Deco), time to surface (TTS), the calculated ceiling, as well as the calculated ceiling for several Bühlmann tissue compartments.

The user has control over the display of several statistics, represented as four buttons on the left of the profile panel. These are:

Clicking this button causes the Information Box to display the Maximum Operating Depth (MOD) of the dive, given the gas mixture used. MOD is dependent on the oxygen concentration in the breathing gas. For air (21% oxygen) it is around 57 m. Below the MOD there is a markedly increased risk of exposure to the dangers associated with oxygen toxicity.

Clicking this button causes the Information Box to display the No-deco Limit (NDL) or the Total Time to Surface (TTS). NDL is the time duration that a diver can continue with a dive, given the present depth, that does not require decompression (that is, before an ascent ceiling appears). Once one has exceeded the NDL and decompression is required (that is, there is an ascent ceiling above the diver, then TTS gives the number of minutes required before the diver can surface. TTS includes ascent time as well as decompression time.

Clicking this button causes the Information Box to display the Surface Air Consumption (SAC). SAC is an indication of the surface-normalised respiration rate of a diver. The value of SAC is less than the real respiration rate because a diver at 10m uses breathing gas at a rate roughly double that of the equivalent rate at the surface. SAC gives an indication of breathing gas consumption rate independent of the depth of the dive so that the respiratory rates of different dives can be compared. The units for SAC is litres/min or cub ft/min.

Clicking this button displays the Equivalent Air Depth (EAD) for nitrox dives as well as the Equivalent Narcotic Depth (END) for trimix dives. These are numbers of importance to divers who use breathing gases other than air. Their values are dependent on the composition of the breathing gas. The EAD is the depth of a hypothetical air dive that has the same partial pressure of nitrogen as the current depth of the nitrox dive at hand. A nitrox dive leads to the same decompression obligation as an air dive to the depth equalling the EAD. The END is the depth of a hypothetical air dive that has the same sum of partial pressures of the narcotic gases nitrogen and oxygen as the current trimix dive. A trimix diver can expect the same narcotic effect as a diver breathing air diving at a depth equalling the END.

Figure (B) above shows an information box with a nearly complete set of data.

5. Organising the logbook (Manipulating groups of dives)

5.1. The Dive List context menu

Many actions within Subsurface are dependent on a context menu used mostly to manipulate groups of dives. The context menu is found by selecting a dive or a group of dives and then right-clicking.

The context menu is used in many manipulations described below.

5.1.1. Customising the information showed in the Dive List panel

The default information in the Dive List includes, for each dive, Dive_number, Date, Rating, Dive_depth, Dive_duration and Dive_location. This information can be contolled and changed by right-clicking on the header bar of the Dive List. For instance, a right-click on the Date header brings up a list of items that can be shown in the dive list (see above). Select an item to be shown in the Dive List or to be deleted from the dive list, and the list is immediately updated accordingly. Preferences for information shown in the Dive List is saved and used when Subsurface is re-opened.

5.1.2. Selecting dives from a particular dive site

Many divers have long dive lists and it may be difficult to locate all the dives at a particular site. By pressing Ctl-F on the keyboard, a text box is opened at the top left hand of the Dive List. Type the name of a dive site in this text box and the Dive List is immediately filtered to show only the dives for that site.

5.2. Renumbering the dives

Dives are normally numbered incrementally from non-recent dives (low sequence numbers) to recent dives (having the highest sequence numbers). The numbering of the dives is not always consistent. For instance, when non-recent dives are added to the dive list the numbering does not automatically follow on because of the dives that are more recent in date/time than the newly-added dive with an older date/time. Therefore, one may sometimes need to renumber the dives. This is performed by selecting (from the Main Menu) Log → Renumber. Users are given a choice with respect to the lowest sequence number to be used. Completing this operation results in new sequence numbers (based on date/time) for the dives in the Dive List panel.

5.3. Grouping dives into trips and manipulating trips

For regular divers, the dive list can rapidly become very long. Subsurface can group dives into trips. It performs this by grouping dives that have date/times that are not separated in time by more than two days, thus creating a single heading for each diving trip represented in the dive log. Below is an ungrouped dive list (A, on the left) as well as the corresponding grouped dive list comprising five dive trips (B, on the right):

Grouping into trips allows a rapid way of accessing individual dives without having to scan a long lists of dives. In order to group the dives in a dive list, (from the Main Menu) users must select Log → Autogroup. The Dive List panel now shows only the titles for the trips.

5.3.1. Editing the title and associated information for a particular trip

Normally, in the dive list, minimal information is included in the trip title. More information about a trip can be added by selecting its trip title from the Dive List. This shows a Trip Notes tab in the Dive Notes panel. Here users can add or edit information about the date/time, the trip location and any other general comments about the trip as a whole (e.g. the dive company that was dived with, the general weather and surface conditions during the trip, etc.). After entering this information, users should select Save from the buttons at the top right of the Trip Notes tab. The trip title in the Dive List panel should now reflect some of the edited information.

5.3.2. Viewing the dives during a particular trip

Once the dives have been grouped into trips, users can expand one or more trips by clicking the arrow-head on the left of each trip title. This expands the selected trip, revealing the individual dives performed during the trip.

5.3.3. Collapsing or expanding dive information for different trips

If a user right-clicks after selecting a particular trip in the dive list, the resulting context menu allows several possibilities to expand or collapse dives within trips. This includes expanding all trips, collapsing all trips and collapsing all trips except the selected one.

5.3.4. Merging dives from more than one trip into a single trip

By right-clicking on a selected trip title in the Dive List panel, a context menu shows up that allows the merging of trips by either merging of the selected trip with the trip below or with the trip above.

5.3.5. Splitting a single trip into more than one trip

If a trip includes five dives, the user can split this trip into two trips (trip 1: top 3 dives; trip 2: bottom 2 dives) by selecting and right-clicking the top three dives. The resulting context menu allows the user to create a new trip by choosing the option Create new trip above. The top three dives are then grouped into a separate trip. The figures below shows the selection and context menu on the left (A) and the completed action on the right (B):

5.4. Manipulating single dives

5.4.1. Delete a dive from the dive log

Dives can be permanently deleted from the dive log by selecting and right-clicking them to bring up the context menu, and then selecting Delete dive(s). Typically this would apply to a case where a user wishes to delete workshop calibration dives of the dive computer or dives of extremely short duration.

5.4.2. Unlink a dive from a trip

Users can unlink dives from the trip to which they belong. In order to do this, select and right-click the relevant dives to bring up the context menu. Then select the option Remove dive(s) from trip. The dive(s) now appear immediately above the trip to which they belonged.

5.4.3. Add a dive to the trip immediately above

Selected dives can be moved from the trip to which they belong and placed within the trip immediately above the currently active trip. To do this, select and right-click the dive(s) to bring up the context menu, and then select Add dive(s) to trip immediately above.

5.4.4. Shift the start time of dive(s)

Sometimes it is necessary to adjust the start time of a dive. This may apply to situations where dives are performed in different time zones or when the dive computer has an erroneous time. In order to do this, user must select and right-click the dive(s) to be adjusted. This action brings up the context menu on which the Shift times option should be selected. User must then specify the time (in hours and minutes) by which the dives should be adjusted and click on the option indicating whether the time adjustment should be forwards or backwards.

5.4.5. Merge dives into a single dive

Sometimes a dive is briefly interrupted, e.g. if a diver returns to the surface for a few minutes, resulting in two or more dives being recorded by the dive computer and appearing as different dives in the Dive List panel. Users can merge these dives onto a single dive by selecting the appropriate dives, right-clicking them to bring up the context menu and then selecting Merge selected dives. It may be necessary to edit the dive information in the Dive Notes panel to reflect events or conditions that apply to the merged dive. The figure below shows the depth profile of two such dives that were merged:

6. Exporting the dive log or parts of the dive log

The export function can be reached by selecting File → Export, which brings up the Export dialog. This dialog always gives two options: save ALL dives, or save only the dives selected in Dive List panel of Subsurface. Click the appropriate radio button (see images below).

A dive log or part of it can be saved in three formats:

Subsurface XML format. This is the native format used by Subsurface.
Universal Dive Data Format (UDDF). Refer to http://uddf.org for more information. UDDF is a generic format that enables communication among many dive computers and computer programs.
Divelogs.de, an Internet-based dive log repository. In order to upload to Divelogs.de, one needs a user-ID as well as a password for Divelogs.de. Log into http://en.divelogs.de and subscribe to this service in order to upload dive log data from Subsurface.
CSV format, that includes the most critical information of the dive profile. Included information of a dive is: dive number, date, time, duration, depth, temperature and pressure.
Worldmap format, an HTML file with a world map upon which each dive and some information about it are indicated. This map is not editable.
HTML format, in which the dive(s) are stored in HTML files, readable with an Internet browser. Most modern web browsers are supported, but Javascript must be enabled. This generated HTML file is not intended to be edited by the users. The HTML dive log contains most of the information and also contains a search option to search the dive log. HTML export is specified on the second tab of the Export dialog (image B above).
General Settings, under the HTML tab, provides the following options:
- Subsurface Numbers: if this option is checked, the dive(s) are exported with the numbers associated with them in Subsurface, Otherwise the dive(s) will be numbered starting from 1.
- Minimum Javascript: This will minimize the Javascript produced with the file, some functionality will be lost.
- Export List only: a list of dives will only be exported and the detailed dive information will not be available.
Under Style Options some style-related options are available like font size and theme.

Export to other formats can be achieved through third party facilities, for instance www.divelogs.de.

7. Keeping a Subsurface dive log in the Cloud

For each diver, dive log information is highly important. Not only is it a record of diving activities for one’s own pleasure, but it is important information required for admission to further training courses or (sometimes) even diving sites. The security of the dive log is therefore critical. In order to have a dive log that is resistant to failure of a home computer hard drive, loss or theft of equipment, the Cloud is an obvious solution. This also has the added benefit that one can access one’s dive log from anywhere in the world without having to carry it with oneself. For this reason, facilities such as divelogs.de and Diving Log offer facilities to store dive log information on the Internet. Although Subsurface does not offer integrated Cloud storage of dive logs, it is simple to achieve this using several of the existing facilities on the Internet.

For instance Dropbox offers a free application that allows files on the Dropbox servers to be seen as a local folder on one’s desktop computer.

Currently there are no costs involved for this service. In this case, one can store one’s dive log on Dropbox in a totally seamless way: a dive log in one’s Dropbox folder can be opened and saved directly by Subsurface and it can be accessed from any place with Internet access. Dropbox (Windows, Mac and Linux) can be installed by accessing the Install Page on the Dropbox website . Alternatively one can use Dropbox as a mechanism to backup one’s dive log. To Store a dive log in the Cloud, select File→Save as from the Subsurface main menu, navigate to the Dropbox folder and select the Save button. To access the dive log in the Cloud, select File→Open Logbook from the Subsurface main menu and navigate to the dive log file in the Dropbox folder and select the Open button. Both options Open and Save are done on the local copy of the dive log saved on one’s computer’s folder Dropbox, so there’s no need of direct internet conexion. If the local copy is modified, e.g. adding a dive, the copy in the Dropbox server in the Cloud will be automatically updated when connecting to the internet.

8. Printing a dive log

Subsurface provides a simple interface to print a whole dive log or only a few selected dives, including dive profiles and other contextual information.

Before printing, two decisions are required:

Should the whole dive log be printed or only part of it? If only part of the dive log is required, then the user must select the required dives from the Dive List panel.
What gas partial pressure information is required on the dive profile? Users should select the appropriate information from the Main Menu: File→Preferences→Graph.

Now the print options should be selected to match the user’s needs. To do this, user should select File→Print from the Main menu. The following dialogue appears (see the image on the left [A], below).

Under Print type users need to select one of three options:

Print the complete Dive List: to do this, Table Print should be selected.
Print the selected dives (dive profiles and all other information) at 6 dives per printed page: to do this, users should select 6 dives per page.
Print the selected dives (dive profiles and all other information) at 2 dives per printed page: to do this, users should select 2 dives per page.
Print the selected dives (dive profiles and all other information) at 1 dive per printed page: to do this, users should select 1 dive per page.

Under Print options users need to select:

Printing only the dives that have been selected from the dive list prior to activating the print dialogue, achieved by checking the box Print only selected dives.
Printing in colour, achieved by checking the box with Print in colour.

The Ordering affects the layout of the page (or part of it) for each dive. The dive profile could be printed at the top of each dive, with the textual information underneath, or it could be printed with the textual information at the top with the dive profile underneath. Users should select the appropriate option in the print dialogue. See the image below which has a layout with text below the dive profile.

Users can Preview the printed page by selecting the Preview button on the dialogue. After preview, changes to the options in the print dialogue can be made, resulting in a layout that fits personal taste.

Next, select the Print button in the dialogue. This activates the regular print dialogue used by the user operating system (image [B] in the middle, above), allowing them to choose a printer and to set its properties (image [C] on the right, above). It is important to set the print resolution of the printer to an appropriate value by changing the printer properties. Finally, one can print the dives. Below is a (rather small) example of the output for one particular page.

Several paid services exist on the Internet (e.g. Google, Amazon) where the same process could be used for the Cloud-based storage of dive logs.

9. Setting user Preferences for Subsurface

There are several settings within Subsurface that the user can specify. These are found when selecting File→Preferences. The settings are performed in five groups: Defaults, Units, Graph, Language and Network. All five sections operate on the same principles: the user must specify the settings that are to be changed, then these changes are saved using the Apply button. After applying all the new settings users can then leave the settings panel by selecting OK.

9.1. Defaults

There are several settings in the Defaults panel:

Lists and tables: Here one can specify the font type and font size of the Dive Table panel. By decreasing the font size of the Dive Table, users can see more dives on a screen.
Dives: For the Default Dive File one need to specify the directory and file name of one’s electronic dive log book. This is a file with filename extension .xml. When launched, Subsurface will automatically load the specified dive log book.
Display invalid: Dives can be marked as invalid (when a user wishes to hide dives that he/she don’t consider valid dives, e.g. pool dives, but still want to keep them in the dive log). This controls whether those dives are displayed in the dive list.
Default cylinder: Here users can specify the default cylinder listed in the Equipment tab of the Dive Notes panel.
Animations: Some actions in showing the dive profile are performed using animations. For instance, the axis values for depth and time change from dive to dive. When viewing a different dive, these changes in axis characteristics do not happen instantaneously, but are animated. The Speed of animations can be controlled by setting this slider with faster animation speed to the left, with a 0 value representing no animation at all.
Subsurface web service: When one subscribes to the Subsurface web service, a very long and hard-to-remember userID is issued. This is the place to save that userID. By checking the option Save User ID locally?, one ensures that a local copy of that userID is saved.
Clear all settings: As indicated in the button below this heading, all settings are cleared and set to default values.

9.2. Units

Here user can choose between metric and imperial units of depth, pressure, volume, temperature and mass. By selecting the Metric or Imperial radio button at the top, users can specify that all units are in the chosen measurement system. Alternatively, if one selects the Personalise radio button, units can be selected independently, with some units in the metric system and others in imperial.

9.3. Graph

This panel allows two type of selections:

Show: Here users can specify the amount of information shown as part of the dive profile:
- Thresholds: Subsurface can display the nitrogen, oxygen and the helium partial pressures during the dive. These are enabled using the toolbar on the left hand side of the Dive Profile panel. For each of these graphs users can specify a threshold value on the right-hand side of the Preferences panel. If any of the graphs go above this threshold level, the graph is highlighted in red, indicating that the threshold has been exceeded.
- Draw dive computer reported ceiling red: This checkbox allows exactly what it says. Not all dive computers report ceiling values. If the dive computer does report it, it may differ from the ceilings calculated by Subsurface. This is because of the different algorithms and gradient factors available for calculating ceilings, as well as the dynamic way that a dive computer can calculate ceilings during a dive.
- Show unused cylinders in Equipment Tab: This checkbox allows display of information about unused cylinders when viewing the Equipment Tab. Conversely, if this box is not checked, and any cylinders entered using the Equipment Tab are not used (e.g. there was no gas switch to such a cylinder), then these cylinders are omitted from that list.
- Show average depth: Activating this checkbox causes Subsurface to draw a red line across the dive profile, indicating the mean depth of the dive.
Misc:
- Gradient Factors:* Here users can set the gradient factors used while diving. GF_Low is the gradient factor at depth and GF_High is used just below the surface. At intermediate depths gradient factors between GF_Low and GF_High are used. Gradient factors add conservatism to the nitrogen exposure during a dive, in a similar way that many dive computers have a conservatism setting. The lower the value of a gradient factor, the more conservative the calculations are with respect to nitrogen loading and the deeper the ascent ceilings are. Gradient factors of 20/60 are considered conservative and values of 60/90 are considered harsh. Checking GFLow at max depth box causes GF_Low to be used at the deepest depth of a dive. If this box is not checked, GF_Low is applied at all depths deeper than the first deco stop. For more information see:
- Understanding M-values by Erik Baker, Immersed Vol. 3, No. 3.
- Gradient factors for dummies, by Kevin Watts

9.4. Language

Choose a language that Subsurface will use.

A checkbox allows one to use the System Default language which in most cases will be the correct setting; with this Subsurface simply runs in the same language / country settings as the underlying OS. If this is for some reason undesirable users can uncheck this checkbox and pick a language / country combination from the list of included localizations. The Filter text box allows one to list similar languages. For instance there are several system variants of English or French. This particular preference requires a restart of Subsurface to take effect.

9.5. Network

This panel facilitates communication between Subsurface and data sources on the Internet.

This is important, for instance, when Subsurface needs to communicate with Internet services such as the Subsurface Companion app or data export/import from Divelogs.de. These Internet requirements are determined by one’s type of connection to the Internet and by the Internet Service Provider (ISP) used. One’s ISP should provide the appropriate information. If a proxy server is used for Internet access, the appropriate information needs to be provided here. The type of proxy needs to be selected from the dropdown list. after which the IP address of the host and the appropriate port number should be provided. If the proxy server uses authentication, the appropriate userID and password also needs to be provided so that Subsurface can automatically pass through the proxy server to access the Internet.

10. The Subsurface dive planner

Dive planning is an advanced feature of Subsurface, accessible by selecting Log → Plan Dive from the main menu. It allows calculation of nitrogen load during a dive by using the Bühlmann ZH-L16 algorithm with the addition of gradient factors as implemented by Erik Baker.

The Subsurface dive planner IS CURRENTLY EXPERIMENTAL and assumes the user is already familiar with the Subsurface user interface. It is explicitly used under the following conditions:

The user is conversant with dive planning and has the necessary training to perform dive planning.
The user plans dives within his/her certification limits.
Dive planning makes large assumptions about the characteristics of the average person and cannot compensate for individual physiology or health or personal history or life style characteristics.
The safety of a dive plan depends heavily on the way in which the planner is used.
The user is familiar with the user interface of Subsurface.
A user who is not absolutely sure about any of the above requirements should not use this feature.

10.1. The Subsurface dive planner screen

Like the Subsurface dive log, the planner screen is divided into several sections (see image below). The setup parameters for a dive are entered into the several sections on the left hand side of the screen. The setup is divided into several sections: Available Gases, Rates, Planning, Gas Options and Dive Notes.

At the top right hand is a green design panel upon which the profile of the dive can be manipulated directly by dragging and clicking as explained below. This feature makes the Subsurface dive planner unique in ease of use.

At the bottom right is a text panel with a heading of Dive Plan Details. This is where the details of the dive plan are provided in a way that can easily be copied to other software. This is also where any warning messages about the dive plan are printed.

10.2. Initiating dive planning

The dive planner comprises two parts: constructing a dive plan and evaluating that dive plan. To perform dive planning, perform these steps:

Clear the existing dive log by creating a new planning log. This is achieved by selecting File → New logbook from the main menu. This way, dive plans are kept separate from the existing dive log of completed dives.
In the top left-hand area of the screen, ensure that the constant dive parameters are appropriate. These are: Start date and time of the dive, Atmospheric Pressure and Altitude above sea level of the dive site. The atmospheric pressure can also be entered as an altitude in metres, assuming an atmospheric pressure of 1.013 bar.
In the table labelled Available Gases, add the information of the cylinders to be used as well as the gas composition within that cylinder. This is done in a similar way as for providing cylinder data for dive logs. Choose the cylinder type by double clicking the cylinder type and using the dropdown list, then specify the work pressure of this cylinder. By leaving the oxygen concentration (O2%) filed empty, the dive gas is assumed to be air. Otherwise enter the oxygen and/or helium concentration in the boxes provided in this dialogue. Add additional cylinders by using the "+" icon to the top righthand of the dialogue.
The dialogue indicating Dive Planner Points is usually not used at this stage of the dive planning.

10.3. Managing nitrogen, oxygen and gas consumption

The planning is performed in three stages:

a) Nitrogen management: This is performed by specifying the rates for descent and ascent, as well as the gradient factors (GFLow and GFHigh) under the headings Rates and Planning to the bottom left of the planning screen. Initially, the GFHigh and GFLow values in the Preferences panel of Subsurface is used. If these are changed within the planner (see Gas Options within the planner), the new values are used without changing the original specifications in the Preferences. Gradient Factor settings strongly affect the calculated ceilings and their depths. A very low GFLow value brings about decompression stops early on during the dive.
- For more information about Gradient factors, see the section on Gradient Factor Preference settings. For more information external to this manual see:
  - Understanding M-values by Erik Baker, Immersed Vol. 3, No. 3.
  - Gradient factors for dummies, by Kevin Watts
  - Deco for Divers, by Mark Powell (2008). Aquapress Southend-on-Sea, UK. ISBN 10: 1-905492-07-3. An excellent non-technical review.
- The ascent rate is critical for nitrogen off-gassing at the end of the dive and is specified for several depth ranges, utilising the average (or mean) depth as a yardstick. The mean depth of the dive plan is indicated on the dive profile in the green panel of the dive planner. Ascent rates at deeper levels are often in the range of 8-12 m/min, while ascent rates near the surface are often in the range of 4-9 m/min. The descent rate is also specified. If the option Drop to first depth is activated, then the descent phase of the planned dive will be at the maximal descent rate specified in the Rates section of the dive setup.
b) Oxygen management: In the Gas Options part of the dive specification, the maximum partial pressure for oxygen needs to be specified for the bottom part of the dive (bottom po2) as well as for the decompression part of the dive (deco po2). The most commonly used values are 1.4 bar for the bottom part of the dive and 1.5 bar for any decompression stages. Normally, a partial pressure of 1.5 bar is not exceeded. PO2 settings and the depth at which switching to a gas takes place can also be edited in the Available Gases dialog. Normally the planner decides on switching to a new gas when, during ascent, the partial pressure of the new gas has decreased to 1.6 bar.
c) Gas management: One needs keep within the limits of the amount of gas contained in the dive cylinder(s), allowing for an appropriate margin for safe return to the surface, possibly sharing with a buddy. Under the Gas Options heading, specify the best (but conservative) estimate of your surface-equivalent air consumption (SAC, also termed RMV) in litres/min (or cft/min, determined by the settings of the Preferences tab of Subsurface. Specify the SAC during the bottom part of the dive (bottom SA) as well as during the decompression or safety stops of the dive (deco SAC). Values of 20-30 l/min are common. For good gas management, a thumbsuck guess is not sufficient and one needs to monitor one’s gas consumption on a regular basis, dependent on different dive conditions and/or equipment. The planner will calculate the total volume of gas used during the dive and will issue a warning if one exceeds the total amount of gas available. Good practice demands that one does not dive to the limit of the gas supply but that an appropriate reserve is kept for unforeseen circumstances. For technical diving, this reserve can be up to 66% of the total available gas.
Now (at last) one can start the detailed time-depth planning of the dive. Subsurface offers a unique graphical interface for performing this part of the planning. The mechanics of doing this is similar to hand-entering a dive profile in the dive log part of Subsurface. Upon activating the planner, a default dive of depth 15 m for 40 min is offered in the green design surface to the top right hand of the screen. The white dots (waypoints) on the profile can be dragged with a mouse. Create more waypoints by double-clicking on the profile line and ensuring that the profile reflects the intended dive. Drag the waypoints to represent the depth and duration of the dive. If any of the management limits (for nitrogen, oxygen or gas) is exceeded, the surface above the dive profile changes from BLUE to RED.
Each waypoint on the dive profile creates a Dive Planner Point in the table on the left of the dive planner panel. Ensure that the Used Gas value in each row of that table corresponds to one of the gas mixtures specified in the table with Available Gases immediately above the Dive Planner Points. Add new waypoints until the main features of the dive have been completed, e.g. the bottom time segment and deep stops (if these are implemented). Leave the remaining waypoints on the ascent to Subsurface. In most cases Subsurface computes additional way points in order to fulfil decompression requirements for that dive.
A waypoint can be moved by selecting that waypoint and by using the arrow keys.
The waypoints listed in the Dive Planner Points dialogue can be edited by hand in order to obtain a precise presentation of the dive plan. In fact, one can create the whole dive profile by editing the Dive Planner Points dialog.
Indicate any changes in gas cylinder used by indicating gas changes as explained in the section hand-creating a dive profile. These changes should reflect the cylinders and gas compositions defined in the table with Available Gases. If two or more gases are used, automatic gas switches will be suggested during the ascent to the surface. However, these changes can be deleted by right-clicking the gas change and by manually creating a gas change by right-clicking on the appropriate waypoint.

Below is an example of a dive plan to 45m using EAN26, followed by an ascent using EAN50 and using the settings as described above.

Once the above has been completed, one can save it by clicking the Save button towards the bottom left of the green design panel. The saved dive plan will appear in the Dive List panel of Subsurface.

10.4. The dive plan details

On the bottom right of the dive planner, under Dive Plan Details, the exact details of the dive plan are provided. These details may be modified by checking any of the options under the Dive Notes section of the dive planner, immediately to the left of the Dive Plan Details. If a Verbatim diveplan is requested, a detailed sentence-level explanation of the dive plan is given. If any of the management specifications have been exceeded during the planning, a warning message is printed underneath the dive plan information.

If the option Display segment duration is checked, then the duration of each depth level is indicated in the Dive Plan Details. This duration INCLUDES the transition time to get to that level. However, if the Display transition in deco option is checked, the transitions are shown separately from the segment durations at a particular level.

10.5. Printing the dive plan

Selecting the Print button in the planner allows printing of the Dive Plan Details for wet notes. Alternatively one can cut and paste the Dive Plan Details for inclusion in a text file or word processing document.

Dive plans have many characteristics in common with dive logs (dive profile, dive notes, etc). After a dive plan has been saved, the dive details and gas calculations are saved in the Dive Notes tab. While a dive plan is being designed, it can be printed using the Print button in the dive planner. This prints the dive details and gas calculations in the Dive Plan Details panel of the dive planner. However, after the plan has been saved, it is represented in a way very similar to a dive log and the gas calculations cannot be accessed in the same way as during the planning process. The only way to print the dive plan is to use the File→Print facility on the main menu in the same way as for dive logs.

10.6. Planning for repetitive dives

Repetitive dives can easily be planned if the dates and start times of the repetitive dive set is specified appropriately in the top left-hand Start Time field. Subsurface calculates the gas loading figures correctly and the effect of the first dive is evaluated on later dives.

If one has just completed a long/deep dive and is planning another dive, then highlight, in the Dive List, the dive that has just been completed and then activate the planner. Depending on the start time of the planned dive, the planner takes into account the gas loading incurred during the completed dive and allows planning within these limitations.

If only a few standard configurations are used (e.g. in GUE), then a template dive can be created conforming to one of the configurations. If one now wishes to plan a dive using this configuration, just highlight the template dive in the Dive List and activate the planner: the planner takes into account the configuration in the highlighted dive.

11. Description of the Subsurface Main Menu items

This section describes the functions and operation of the items in the Main Menu of Subsurface. Several of the items below are links to sections of this manual dealing with the appropriate operations.

11.1. File

New Logbook - Close the currently open dive logbook and clear all dive information.
Open logbook - This opens the file manager in order to select a dive logbook to open.
Save - Save the dive logbook that is currently open.
Save as: - Save the current logbook or the currently selected dives within the present logbook under a different file name.
Close - Close the dive logbook that is currently open.
Export - Export the currently open dive logbook (or the selected dives in the logbook) to one of several formats.
Print - Print the currently open logbook.
Preferences - Set the Subsurface preferences.
Quit - Quit Subsurface.

11.2. Import

Import from dive computer - Import dive information from a dive computer.
Import Log Files - Import dive information from a file in in a Subsurface-compatible format.
Import GPS data from Subsurface Service - Load GPS coordinates from the Subsurface mobile phone app.
Import from Divelogs.de - Import dive information from www.Divelogs.de.

11.3. Log

Add Dive - Manually add a new dive to the Dive List panel.
Plan Dive - This feature allows the planning of dives.
Renumber - Renumber the dives listed in the Dive List panel.
Auto Group - Group the dives in the Dive List panel into dive trips.
Edit Device Names - Edit the names of dive computers to facilitate your logs.

11.4. View

All - View the four main Subsurface panels simmultaneously.
Dive List - View only the Dive List panel.
Profile - View only the Dive Profile panel.
Info - View only the Dive Notes panel.
Globe - View only the World Map panel.
Yearly Statistics - Display summary statistics about dives during this and past years.
Prev DC - Switch to next dive computer.
Next DC - Switch to previous dive computer.
Full Screen - Toggles Full Screen mode.

11.5. Filter

Select Events - This option is not implemented yet.

11.6. Help

About Subsurface - Show a panel with the version number of Subsurface as well as licensing information.
Check for updates - Find out whether a newer version of Subsurface is available on the Subsurface web site.
User Manual - Open a window showing this user manual.

12. APPENDIX A: Operating system specific information for importing dive information from a dive computer.

12.1. Make sure that the OS has the required drivers installed

The operating system of the desktop computer needs the appropriate drivers in order to communicate with the dive computer in whichever way the dive computer prefers (e.g. bluetooth, USB, infra-red).

On Linux users need to have the correct kernel module loaded. Most distributions will do this automatically, so the user does not need to load kernel modules. However, some communication protocols require an additional driver, especially for rarely used technology such as infra-red.
On Windows, the OS should offer to download the correct driver once the user connects the dive computer to the USB port and operating system sees the equipment for the first time.
On a Mac users sometimes have to manually hunt for the correct driver. For example the correct driver for the Mares Puck devices or any other dive computer using a USB-to-serial interface based on the Silicon Labs CP2101 or similar chip can be found as Mac_OSX_VCP_Driver.zip at the Silicon Labs document and software repository.

12.2. How to Find the Device Name for USB devices and set its write permission

When a user connects the dive computer by using a USB connector, usually Subsurface will either propose a drop down list that contains the correct device name (or mount point for the Uemis Zurich), or it will disable the device select drop down if no device name is needed at all. In the rare cases where this doesn’t work, here are some suggestions of ways to find out what the device name is:

On Windows:

Simply try COM1, COM2, etc. The drop down list should contain all connected COM devices.

On MacOS:

The drop down box should find all connected dive computers.

On Linux:

There is a definitive way to find the port:

Disconnect the USB cable from the dive computer
Open a terminal
Type the command: dmesg and press enter
Plug in the USB cable of the dive computer
Type the command: dmesg and press enter

A message similar to this one should appear:

usb 2-1.1: new full speed USB device number 14 using ehci_hcd
usbcore: registered new interface driver usbserial
USB Serial support registered for generic
usbcore: registered new interface driver usbserial_generic
usbserial: USB Serial Driver core
USB Serial support registered for FTDI USB Serial Device
ftdi_sio 2-1.1:1.0: FTDI USB Serial Device converter detected
usb 2-1.1: Detected FT232BM
usb 2-1.1: Number of endpoints 2
usb 2-1.1: Endpoint 1 MaxPacketSize 64
usb 2-1.1: Endpoint 2 MaxPacketSize 64
usb 2-1.1: Setting MaxPacketSize 64
usb 2-1.1: FTDI USB Serial Device converter now attached to ttyUSB3
usbcore: registered new interface driver ftdi_sio
ftdi_sio: v1.6.0:USB FTDI Serial Converters Driver

The third line from the bottom shows that the FTDI USB adapter is detected and connected to ttyUSB3. This information can now be used in the import settings as /dev/ttyUSB3 which directs Subsurface to the correct USB port.

Ensuring that the user has write permission to the USB serial port:

On Unix-like operating systems the USB ports can only be accessed by users who are members of the dialout group. If one is not root, one may not be a member of that group and will not be able to use the USB port. Let us assume one’s username is johnB.

As root, type: usermod -a -G dialout johnB (Ubuntu users: sudo usermod -a -G dialout johnB) This makes johnB a member of the dialout group.
Type: id johnB This lists all the groups that johnB belongs to and verifies that the appropriate group membership has been created. The dialout group should be listed among the different IDs.

With the appropriate device name (e.g. dev/ttyUSB3) and with write permission to the USB port, the dive computer interface can connect and one should be able to import dives.

12.3. Setting up bluetooth enabled devices

For dive computers communicating through bluetooth like the Heinrichs Weikamp Frog or the Shearwater Predator and Petrel there is a different procedure to get the devices name to communicate with Subsurface. Follow these steps:

For the dive computer, after enabling Bluetooth, ensure it is in Upload mode.

For Bluetooth pairing of the dive computer, refer to the manufacturer’s user guide. When using a Shearwater Predator/Petrel, select Dive Log → Upload Log and wait for the Wait PC message.

Pair the Subsurface computer with the dive computer.

On Windows:

Bluetooth is most likely already enabled. For pairing with the dive computer choose Control Panel→Bluetooth Devices→Add Wireless Device. This should bring up a dialog showing your dive computer (in Bluetooth mode) and allowing pairing. Right click on it and choose Properties→COM Ports to identify the port used for your dive computer. If there are several ports listed, use the one saying "Outgoing" instead of "Incoming".

For downloading to Subsurface, the Subsurface drop-down list should contain this COM port already. If not, enter it manually.

Note: If there are issues afterwards when downloading from the dive computer using other software, remove the existing pairing with the dive computer.

On MacOS:

Click on the Bluetooth symbol in the menu bar and select Set up Bluetooth Device…. The dive computer should then show up in the list of devices. Select it and go through the pairing process. This step should only be needed once for initial setup.

Once the pairing is completed the correct device is shown in the Device or Mount Point drop-down in the Subsurface Import dialog.

On Linux

Ensure Bluetooth is enabled on the Subsurface computer. On most common distributions this should be true out of the box and pairing should be straight forward. For instance, Gnome3 shows a Bluetooth icon in the upper right corner of the desktop where one selects Set up New Device. This should show a dialog where one can select the dive computer (which already should be in Bluetooth mode) and pair it. If a PIN is required, try manually setting 0000.

In the rare cases where the above is not true, then depending on your system, try initd or systemd. This might be different and also involve loading modules specific to your hardware. In case your system is running systemd, manually run systemctl start bluetooth.service to enable it, in case of initd, run something like rc.config start bluetoothd or /etc/init.d/bluetooth start.

One may also use a manual approach by using such commands:

hciconfig shows the Bluetooth devices available on your computer (not dive computer), most likely one will see a hci0, if not try hcitool -a to see inactive devices and run sudo hciconfig hci0 up to bring them up.
hcitool scanning gets a list of bluetooth enabled client devices, look for the dive computer and remember the MAC address are shown there
bluez-simple-agent hci0 10:00:E8:C4:BE:C4 pairs the dive computer with the bluetooth stack of the Subsurface computer, copy/paste the MAC address from the output of hcitool scanning

Unfortunately on Linux binding to a communication device has to be done manually by running:

rfcomm bind /dev/rfcomm0 10:00:E8:C4:BE:C4 binds the dive computer to a communication device in the desktop computer, in case rfcomm is already taken use rfcomm1 or up. IMPORTANT: Copy/paste the MAC address from the output of hcitool scanning, the MAC address shown above will not work.

For downloading dives in Subsurface specify the device name connected to the MAC address in the last step above, e.g. /dev/rfcomm0.

13. APPENDIX B: Dive Computer specific information for importing dive information.

13.1. Import from a Uemis Zurich

Subsurface downloads the information stored on the SDA (the built-in file system of the Uemis) including information about dive spots and equipment. Buddy information is not yet downloadable. Things are very similar to a normal USB-connected dive computer (the Uemis is one of those that recharge when connected to the USB port). The main difference is that one does not enter a device name, but instead the location where the UEMISSDA file system is mounted once connected to the dive computer. On Windows this is a drive letter ( often E: or F:), on a Mac this is /Volumes/UEMISSDA and on Linux systems this differs depending on the distribution. On Fedora it usually is /var/run/media/<your_username>/UEMISSDA. In all cases Subsurface should suggest the correct location in the drop down list.

After selecting the above device name, download the dives from the Uemis Zurich. One technical issue with the Uemis Zurich download implementation (this is a Uemis firmware limitation, not a Subsurface issue) is that one cannot download more than about 40-50 dives without running out of memory on the SDA. This will usually only happen the very first time one downloads dives from the Uemis Zurich. Normally when downloading at the end of a day or even after a dive trip, the capacity is sufficient. If Subsurface displays an error that the dive computer ran out of space the solution is straight forward. Disconnect the SDA, turn it off and on again, and reconnect it. You can now retry (or start a new download session) and the download will continue where it stopped previously. One may have to do this more than once, depending on how many dives are stored on the dive computer.

13.2. Importing dives from the Uwatec Galileo

The Uwatec Galileo dive computers use infra red (IrDA) communication between the dive computer and Subsurface. The Uwatec hardware uses a USB dongle based on the serial infra-red (SIR) protocol and the MSC7780 IrDA controller manufactured by MosChip and marketed by Scubapro and some electronics companies. Under Linux, the kernel already provides for communication using the IrDA protocol. However, the user additionally needs to load a driver for the IrDA interface with the dive computer. The easiest way is to load the irda-tools package from the Linux IrDA Project. After the installation of the irda-tools, the root user can specify a device name from the console as follows: irattach irda0

After executing this command, Subsurface will recognise the Galileo dive computer and download dive information.

Under Windows, a similar situation exists. Drivers for the MCS7780 are available from some Internet web sites e.g. www.drivers-download.com.

For the Apple Mac, IrDA communication via the MCS7780 link is not available for OSX 10.6 or higher.

13.3. Importing dives from Heinrichs Weikamp DR5

When mounted as a USB drive the Heinrichs Weikamp DR5 saves a single UDDF file for every dive. Mark all the dives you’d like to import or open. Note: The DR5 does not seem to store gradient factors nor deco information, so for Subsurface it is not possible to display them. Adjust the gradient factors in the Tec Settings in Subsurface to generate a deco overlay in the Subsurface Dive Profile panel but please note that the deco calculated by Subsurface will most likely differ from the one displayed on the DR5.

13.4. Import from Shearwater Predator using Bluetooth

Using a Shearwater Predator one may be able to pair Bluetooth but then encounter issues when downloading, showing errors like Slip RX: unexp. SLIP END on the Predator. This might also arise when using other dive log software and operating systems other than Linux. We have no detailed idea about the source and how to fix this, but it is reported to be solved sometimes by one of these steps:

use the Bluetooth dongle which came with the Shearwater Predator instead of the built-in one of the Subsurface computer
switch to different Bluetooth drivers for the same hardware
switch off WiFi while using Bluetooth

14. APPENDIX C: Exporting Dive log information from external dive log software.

The import of dive log data from external dive log software is mostly performed using the dialogue found by selecting Import from the Main Menu, then clicking on Import Log Files. This is a single-step process, more information about which can be found here. However, in some cases, a two-step process may be required:

Export the foreign dive log data to format that is accessible from Subsurface.
Import the accessible dive log data into Subsurface.

This appendix provides some information about approaches to export dive log data from foreign dive log software. The procedures below mostly apply to Linux and/or Windows.

14.1. Exporting dives from Suunto Divemanager (DM3 and DM4)

Divemanager 3 (DM3) is an older version of the Suunto software. More recent Suunto dive computers use Divemanager 4 (DM4). The two versions of Divemanager use different methods and different file naming conventions to export dive log data.

Divemanager 3 (DM3):

Start Suunto Divemanager 3 and log in with the name containing the logs
Do not start the import wizard to import dives from the dive computer.
In the navigation tree on the left side of the program-window, select the appropriate dives.
Within the list of dives, select the dives you would like to import later:
- To select certain dives: hold ctrl and click the dive
- To select all dives: Select the first dive, hold down shift and select the last dive
With the dives marked, use the program menu File → Export
The export pop-up will show. Within this pop-up, there is one field called Export Path.
- Click the browse button next to the field Export Path
  - A file-manager like window pops up
  - Navigate to the directory for storing the Divelog.SDE file
  - Optionally change the name of the file for saving
  - Click Save
- Back in the Export pop-up, press the button Export
The dives are now exported to the file Divelog.SDE.

Divemanager 4 (DM4):

To export divelog from Suunto DM4, one needs to locate the DM4 database where the dives are stored. the user can either look for the original database or make a backup of the dives. Both methods are described here.

Locating the Suunto DM4 database:

Start Suunto DM4
Select Help → About
Click Copy after text Copy log folder path to clipboard
Now open Windows Explorer
Paste the address to the path box at the top of the File Explorer
The database is called DM4.db

Backing up Suunto DM4:

Start Suunto DM4
Select File - Create backup
From the file menu select the location and name for the backup, we’ll use DM4 in here with the default extension .bak
Click Save
The dives are now exported to the file DM4.bak

14.2. Exporting from Mares Dive Organiser V2.1

Mares Dive Organiser is a Windows application. The dive log is kept as a Microsoft SQL Compact Edition data base with a .sdf filename extension. The data base includes all Dive Organiser-registered divers on the particular computer and all Mares dive computers used. The safest way to obtain a copy of the dive data base is to export the information to another compatible format which can be imported into Subsurface.

Within Dive Organiser, select Database → Backup from the main menu and back up the data base to the desk top. This creates a zipped file DiveOrganiserxxxxx.dbf.
Rename the file to DiveOrganiserxxxxx.zip. Inside the zipped directory is a file DiveOrganiser.sdf.
Extract the .sdf file from the zipped folder to your Desktop.
The password for accessing the .zip file is mares.

14.3. Exporting dives from DivingLog 5.0

Unfortunately DivingLog XML files give us no indication on the preferences set on one’s system. So in order for Subsurface to be able to successfully import XML files from DivingLog one first needs to ensure that DivingLog is configured to use the Metric system (one can easily change this within Diving Log by selecting File → Preferences → Units and Language by clicking the Metric button). Then do the following:

In Divinglog open the File → Export → XML menu
Select the dives to export
Click on the export button and select the filename

15. APPENDIX D: FAQs.

15.1. Subsurface appears to miscalculate gas consumption and SAC

Question: I dived with a 12.2 l tank, starting with 220 bar and ending with 100 bar, and I calculate a different SAC compared what Subsurface calculates. Is Subsurface miscalculating?

Answer: Not really. What happens is that Subsurface actually calculates gas consumption differently - and better - than you expect. In particular, it takes the incompressibility of the gas into account. Traditionally, Gas consumption and SAC should be: consumption = tank size x (start pressure - end pressure)

and that’s true for an ideal gas, and it’s what you get taught in dive theory. But an "ideal gas" doesn’t actually exist, and real gases actually don’t compress linearly with pressure. Also, you are missing the fact that one atmosphere of pressure isn’t actually one bar. So the real calculation is:

consumption = (amount_of_air_at_beginning - amount_of_air_at_end)

where the amount of air is not just "tank size times pressure in bar". It’s a combination of: "take compressibility into account" (which is a fairly small issue under 220 bar - you’ll see more differences when you do high-pressure tanks with 300bar) and "convert bar to atm" (which is the majority of your discrepancy). Remember: one ATM is ~1.013 bar, so without the compressibility, your gas use is:

12.2*((220-100)/1.013)

which is about 1445, not 1464. So there was 19 l too much in your simple calculation that ignored the difference between 1 bar and one ATM. The compressibility does show up above 200 bar, and takes that 1445 down about eight litres more, so you really did use only about 1437 l of air at surface pressure.

So be happy: your SAC really is better than your calculations indicated. Or be sad: your cylinder contains less air than you thought it did. And as mentioned, the "contains less air than you thought it did" really starts becoming much more noticeable at high pressure. A 400 bar really does not contain twice as much air as a 200 bar one. At lower pressures, air acts pretty much like an ideal gas.

15.2. Some dive profiles have time discrepancies with the recorded samples from my dive computer…

Subsurface ends up ignoring surface time for many things (average depth, divetime, SAC, etc). Question: Why do dive durations in my dive computer differ from that given by Subsurface?

Answer: For example, if you end up doing a weight check (deep enough to trigger the "dive started") but then come back up and wait five minutes for your buddies, your dive computer may say that your dive is 50 minutes long - because you have fifty minutes worth of samples - but subsurface will say it’s 45 minutes - because you were actually diving for 45 minutes. It’s even more noticeable if you do things like divemastering the initial OW dives, when you may stay in the water for a long time, but spend most of it at the surface. And then you don’t want that to count as some kind of long dive”.