diff --git a/dive.c b/dive.c
index 4bae24526..019b1d0a4 100644
--- a/dive.c
+++ b/dive.c
@@ -2218,3 +2218,23 @@ void set_userid(char *rUserId)
 		strcpy(prefs.userid, rUserId);
 }
 #undef MAX_USERID_SIZE
+
+int average_depth(struct diveplan *dive)
+{
+	int integral = 0;
+	int last_time = 0;
+	int last_depth = 0;
+	struct divedatapoint *dp = dive->dp;
+
+	while (dp) {
+		if (dp->time) {
+			/* Ignore gas indication samples */
+			integral += (dp->depth + last_depth) * (dp->time - last_time) / 2;
+			last_time = dp->time;
+			last_depth = dp->depth;
+		}
+		dp = dp->next;
+	}
+
+	return integral / last_time;
+}
diff --git a/dive.h b/dive.h
index 13606f39e..b4e21a58a 100644
--- a/dive.h
+++ b/dive.h
@@ -915,6 +915,7 @@ extern depth_t string_to_depth(const char *str);
 extern pressure_t string_to_pressure(const char *str);
 extern volume_t string_to_volume(const char *str, pressure_t workp);
 extern fraction_t string_to_fraction(const char *str);
+extern int average_depth(struct diveplan *dive);
 
 #include "pref.h"
 
diff --git a/planner.c b/planner.c
index 5c0bbecbc..980b221b0 100644
--- a/planner.c
+++ b/planner.c
@@ -576,10 +576,20 @@ static void add_plan_to_notes(struct diveplan *diveplan, struct dive *dive)
 }
 #endif
 
-int ascend_velocity(int depth)
+int ascend_velocity(int depth, int avg_depth, int bottom_time)
 {
 	/* We need to make this configurable */
-	return 10000/60;
+
+	/* As an example (and possibly reasonable default) this is the Tech 1 provedure according
+	 * to http://www.globalunderwaterexplorers.org/files/Standards_and_Procedures/SOP_Manual_Ver2.0.2.pdf */
+
+	if (depth <= 6000)
+		return 1000 / 60;
+
+	if (depth * 4 > avg_depth *3)
+		return 9000 / 60;
+	else
+		return 6000 / 60;
 }
 
 void plan(struct diveplan *diveplan, char **cached_datap, struct dive **divep, bool add_deco)
@@ -599,6 +609,7 @@ void plan(struct diveplan *diveplan, char **cached_datap, struct dive **divep, b
 	bool stopping = false;
 	bool clear_to_ascend;
 	int clock, previous_point_time;
+	int avg_depth, bottom_time;
 
 	set_gf(diveplan->gflow, diveplan->gfhigh, default_prefs.gf_low_at_maxdepth);
 	if (!diveplan->surface_pressure)
@@ -622,6 +633,7 @@ void plan(struct diveplan *diveplan, char **cached_datap, struct dive **divep, b
 		current_cylinder = 0;
 	}
 	depth = dive->dc.sample[dive->dc.samples - 1].depth.mm;
+	avg_depth = average_depth(diveplan);
 
 	/* if all we wanted was the dive just get us back to the surface */
 	if (!add_deco) {
@@ -655,7 +667,7 @@ void plan(struct diveplan *diveplan, char **cached_datap, struct dive **divep, b
 	stopidx += gaschangenr;
 
 	/* Keep time during the ascend */
-	clock = previous_point_time = dive->dc.sample[dive->dc.samples - 1].time.seconds;
+	bottom_time = clock = previous_point_time = dive->dc.sample[dive->dc.samples - 1].time.seconds;
 	gi = gaschangenr - 1;
 
 	while (1) {
@@ -663,7 +675,7 @@ void plan(struct diveplan *diveplan, char **cached_datap, struct dive **divep, b
 		do {
 			/* Ascend to next stop depth */
 			assert(deco_allowed_depth(tissue_tolerance, diveplan->surface_pressure / 1000.0, dive, 1) < depth);
-			int deltad = ascend_velocity(depth) * TIMESTEP;
+			int deltad = ascend_velocity(depth, avg_depth, bottom_time) * TIMESTEP;
 			if (depth - deltad < stoplevels[stopidx])
 				deltad = depth - stoplevels[stopidx];
 
@@ -702,7 +714,7 @@ void plan(struct diveplan *diveplan, char **cached_datap, struct dive **divep, b
 			/* Check if ascending to next stop is clear, go back and wait if we hit the ceiling on the way */
 			clear_to_ascend = true;
 			while (trial_depth > stoplevels[stopidx]) {
-				int deltad = ascend_velocity(trial_depth) * TIMESTEP;
+				int deltad = ascend_velocity(trial_depth, avg_depth, bottom_time) * TIMESTEP;
 				tissue_tolerance = add_segment(depth_to_mbar(trial_depth, dive) / 1000.0, &dive->cylinder[current_cylinder].gasmix, TIMESTEP, po2, dive);
 				if (deco_allowed_depth(tissue_tolerance, diveplan->surface_pressure / 1000.0, dive, 1) > trial_depth - deltad){
 					/* We should have stopped */