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VK1ET : Additions to check fflags

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Implement changes suggested by John/VK1ET

Changes to cprNFunction to ensure fflag {was 'isodd'} is used as a flag.
Fix to decodeCPRrelative to pass 'surface' flag.
This commit is contained in:
Malcolm Robb 2013-04-26 09:49:53 +01:00
parent 2acb0947f0
commit f77a85e8b8
1 changed files with 6 additions and 6 deletions
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12
dump1090.c
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@ -2338,14 +2338,14 @@ int cprNLFunction(double lat) {
else return 1;
}
int cprNFunction(double lat, int isodd) {
int nl = cprNLFunction(lat) - isodd;
int cprNFunction(double lat, int fflag) {
int nl = cprNLFunction(lat) - (fflag ? 1 : 0);
if (nl < 1) nl = 1;
return nl;
}
double cprDlonFunction(double lat, int isodd, int surface) {
return (surface ? 90.0 : 360.0) / cprNFunction(lat, isodd);
double cprDlonFunction(double lat, int fflag, int surface) {
return (surface ? 90.0 : 360.0) / cprNFunction(lat, fflag);
}
/* This algorithm comes from:
@ -2381,7 +2381,7 @@ void decodeCPR(struct aircraft *a, int fflag, int surface) {
int ni = cprNFunction(rlat1,1);
int m = (int) floor((((lon0 * (cprNLFunction(rlat1)-1)) -
(lon1 * cprNLFunction(rlat1))) / 131072.0) + 0.5);
a->lon = cprDlonFunction(rlat1,1,surface) * (cprModFunction(m,ni)+lon1/131072);
a->lon = cprDlonFunction(rlat1, 1, surface) * (cprModFunction(m, ni)+lon1/131072);
a->lat = rlat1;
} else { // Use even packet.
int ni = cprNFunction(rlat0,0);
@ -2444,7 +2444,7 @@ int decodeCPRrelative(struct aircraft *a, int fflag, int surface, double latr, d
}
// Compute the Longitude Index "m"
AirDlon = cprDlonFunction(rlat, fflag, 0);
AirDlon = cprDlonFunction(rlat, fflag, surface);
m = (int) (floor(lonr/AirDlon) +
trunc(0.5 + cprModFunction((int)lonr, (int)AirDlon)/AirDlon - lon/131072));
rlon = AirDlon * (m + lon/131072);