Trim the dive to exclude surface time at beginning and end

We don't change any of the samples, we just don't plot (or consider for
dive time / mean calculations) the samples at the beginning or end of the
dive that are less than a certain threshold under water. Right now that's
an arbitrary 75cm which seems to Do The Right Thing(tm) for the dives I
tried this with - but I'm happy to look at other values if this causes
problems for people with dive computers I do not have access to.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/dive.h b/dive.h
index ff5b37a18..8a79de0b2 100644
--- a/dive.h
+++ b/dive.h
@@ -261,6 +261,7 @@ struct dive {
 	tripflag_t tripflag;
 	dive_trip_t *divetrip;
 	int selected;
+	int start, end;
 	timestamp_t when;
 	char *location;
 	char *notes;
@@ -296,6 +297,8 @@ static inline int depth_to_mbar(int depth, struct dive *dive)
 	return depth / 10.0 * specific_weight + surface_pressure + 0.5;
 }
 
+#define SURFACE_THRESHOLD 750 /* somewhat arbitrary: only below 75cm is it really diving */
+
 /* this is a global spot for a temporary dive structure that we use to
  * be able to edit a dive without unintended side effects */
 extern struct dive edit_dive;