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CPR decoding fixed.

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antirez 2013-01-11 11:17:46 +01:00
parent f3a705f57e
commit b10c8dab35
1 changed files with 10 additions and 6 deletions
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16
dump1090.c
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@ -1400,7 +1400,7 @@ double cprDlonFunction(int i, int isodd) {
* seconds.
*/
void decodeCPR(struct aircraft *a) {
const double AirDlat0 = 6;
const double AirDlat0 = 360.0 / 60;
const double AirDlat1 = 360.0 / 59;
double lat0 = a->even_cprlat;
double lat1 = a->odd_cprlat;
@ -1408,10 +1408,13 @@ void decodeCPR(struct aircraft *a) {
double lon1 = a->odd_cprlon;
/* Compute the Latitude Index "j" */
int j = ((59*lat0 - 60*lat1) / 131072) + 0.5;
int j = floor(((59*lat0 - 60*lat1) / 131072) + 0.5);
double rlat0 = AirDlat0 * (cprModFunction(j,60) + lat0 / 131072);
double rlat1 = AirDlat1 * (cprModFunction(j,59) + lat1 / 131072);
if (rlat0 >= 90 && rlat0 <= 270) rlat0 -= 360;
if (rlat1 >= 90 && rlat1 <= 270) rlat1 -= 360;
/* Check that both are in the same latitude zone, or abort. */
if (cprNLFunction(rlat0) != cprNLFunction(rlat1)) return;
@ -1419,18 +1422,19 @@ void decodeCPR(struct aircraft *a) {
if (a->even_cprtime > a->odd_cprtime) {
/* Use even packet. */
int ni = cprNFunction(rlat0,0);
int m = (((lon0 * (cprNLFunction(rlat0)-1)) -
(lon1 * cprNLFunction(rlat0))) / 131072) + 0.5;
int m = floor((((lon0 * (cprNLFunction(rlat0)-1)) -
(lon1 * cprNLFunction(rlat0))) / 131072) + 0.5);
a->lon = cprDlonFunction(rlat0,0) * (cprModFunction(m,ni)+lon0/131072);
a->lat = rlat0;
} else {
/* Use odd packet. */
int ni = cprNFunction(rlat1,1);
int m = (((lon0 * (cprNLFunction(rlat1)-1)) -
(lon1 * cprNLFunction(rlat1))) / 131072) + 0.5;
int m = floor((((lon0 * (cprNLFunction(rlat1)-1)) -
(lon1 * cprNLFunction(rlat1))) / 131072.0) + 0.5);
a->lon = cprDlonFunction(rlat1,1) * (cprModFunction(m,ni)+lon1/131072);
a->lat = rlat1;
}
if (a->lon > 180) a->lon -= 360;
}
/* Receive new messages and populate the interactive mode with more info. */