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Fix quadrant selection for global CPR surface position decoding.

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This commit is contained in:
Oliver Jowett 2015-01-12 16:26:05 +00:00
parent e1d2af42bb
commit bebc00c257
1 changed files with 12 additions and 3 deletions
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15
mode_s.c
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@ -2528,8 +2528,13 @@ int decodeCPR(struct aircraft *a, int fflag, int surface) {
// No local reference, give up
return (-1);
}
rlat0 += floor(surface_rlat / 90.0) * 90.0; // Move from 1st quadrant to our quadrant
rlat1 += floor(surface_rlat / 90.0) * 90.0;
// Pick the quadrant that's closest to the reference location -
// this is not necessarily the same quadrant that contains the
// reference location. Note there are only two valid quadrants
// here (northern/southern hemisphere)
if ( (rlat0 - surface_rlat) > 45 ) rlat0 -= 90;
if ( (rlat1 - surface_rlat) > 45 ) rlat1 -= 90;
} else {
if (rlat0 >= 270) rlat0 -= 360;
if (rlat1 >= 270) rlat1 -= 360;
@ -2559,7 +2564,11 @@ int decodeCPR(struct aircraft *a, int fflag, int surface) {
}
if (surface) {
a->lon += floor(surface_rlon / 90.0) * 90.0; // Move from 1st quadrant to our quadrant
// Pick the quadrant that's closest to the reference location -
// this is not necessarily the same quadrant that contains the
// reference location.
a->lon += floor( (surface_rlon - a->lon + 45) / 90 ) * 90; // if we are >45 degrees away, move towards the reference position
a->lon -= floor( (a->lon + 180) / 360 ) * 360; // normalize to (-180..+180)
} else if (a->lon > 180) {
a->lon -= 360;
}