Improved depth info for dives without samples

This calculates a mean depth for the dive with a fixed ascent/descent
rate and an assumption that all of the bottom time is at the maximum
depth.  It's not much, but it allows some derived values such as SAC to
make more sense.

The depth profile for such dives is now also generated with the same
assumptions instead of putting the samples at fixed percentages of the
dive duration.

Signed-off-by: Mikko Rasa <tdb@tdb.fi>

2 files changed, 10 insertions, 2 deletions

diff --git a/dive.c b/dive.c
index 9f57aed58..36ee8e78c 100644
--- a/dive.c
+++ b/dive.c
@@ -451,7 +451,12 @@ struct dive *fixup_dive(struct dive *dive)
 		}
 	}
 	if (end < 0)
+	{
+		/* Assume an ascent/descent rate of 9 m/min */
+		int asc_desc_time = dive->maxdepth.mm*60/9000;
+		dive->meandepth.mm = dive->maxdepth.mm*(dive->duration.seconds-asc_desc_time)/dive->duration.seconds;
 		return dive;
+	}
 
 	update_duration(&dive->duration, end - start);
 	if (start != end)
diff --git a/profile.c b/profile.c
index 137ed6f88..614822809 100644
--- a/profile.c
+++ b/profile.c
@@ -1354,12 +1354,15 @@ void plot(struct graphics_context *gc, cairo_rectangle_int_t *drawing_area, stru
 	int nr = dive->samples;
 
 	if (!nr) {
+		/* The dive has no samples, so create a few fake ones.  This assumes an
+		ascent/descent rate of 9 m/min, which is just below the limit for FAST. */
 		int duration = dive->duration.seconds;
 		int maxdepth = dive->maxdepth.mm;
+		int asc_desc_time = dive->maxdepth.mm*60/9000;
 		sample = fake;
-		fake[1].time.seconds = duration * 0.05;
+		fake[1].time.seconds = asc_desc_time;
 		fake[1].depth.mm = maxdepth;
-		fake[2].time.seconds = duration * 0.95;
+		fake[2].time.seconds = duration - asc_desc_time;
 		fake[2].depth.mm = maxdepth;
 		fake[3].time.seconds = duration * 1.00;
 		nr = 4;