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| author |  Doug Junkins <junkins@foghead.com> | 2019-04-30 06:53:31 -0700 |
|---|---|---|
| committer |  bstoeger <32835590+bstoeger@users.noreply.github.com> | 2019-04-30 23:32:50 +0200 |
| commit | 14a763a6a0148a42fad06717bd2532181a54c626 (patch) | |
| tree | d8b71f0c9a2d33d40d60aeccb44e12111abcb2e0 /core/divesite.c | |
| parent | 154792ffd1c217e5c1c9774b5593a753ae553601 (diff) | |
| download | subsurface-14a763a6a0148a42fad06717bd2532181a54c626.tar.gz | |
Bugfix for algorithm in get_distance()
Fixed bug in the Haversine function in get_distance() based on algorithm
at https://www.movable-type.co.uk/scripts/latlong.html and added bounds
to the 'a' term to avoid floating point errors for antipodal points.
Signed-off-by: Doug Junkins <junkins@foghead.com>
Diffstat (limited to 'core/divesite.c')
| -rw-r--r-- | core/divesite.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/core/divesite.c b/core/divesite.c index b5ce99a8d..45601537c 100644 --- a/core/divesite.c +++ b/core/divesite.c @@ -77,15 +77,18 @@ struct dive_site *get_dive_site_by_gps_and_name(char *name, const location_t *lo // Calculate the distance in meters between two coordinates. unsigned int get_distance(const location_t *loc1, const location_t *loc2) { + double lat1_r = udeg_to_radians(loc1->lat.udeg); double lat2_r = udeg_to_radians(loc2->lat.udeg); double lat_d_r = udeg_to_radians(loc2->lat.udeg - loc1->lat.udeg); double lon_d_r = udeg_to_radians(loc2->lon.udeg - loc1->lon.udeg); double a = sin(lat_d_r/2) * sin(lat_d_r/2) + - cos(lat2_r) * cos(lat2_r) * sin(lon_d_r/2) * sin(lon_d_r/2); + cos(lat1_r) * cos(lat2_r) * sin(lon_d_r/2) * sin(lon_d_r/2); + if (a < 0.0) a = 0.0; + if (a > 1.0) a = 1.0; double c = 2 * atan2(sqrt(a), sqrt(1.0 - a)); - // Earth radious in metres + // Earth radius in metres return lrint(6371000 * c); } |