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VK1ET : More Decoding of DF-17 ground reports

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Extend the DF-17 CPR decoding to use User Lat/Lon for ground positions.

Also start implementing a bFlags structure variable to indicate which
fields in the mm and a data structures contain valid values.
This commit is contained in:
Malcolm Robb 2013-05-09 15:06:07 +01:00
parent cc464b0a34
commit a3d62f96b7
1 changed files with 38 additions and 14 deletions
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52
dump1090.c
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@ -105,6 +105,10 @@
#define MODES_USER_LATLON_VALID (1<<0)
#define MODES_ACFLAGS_LATLON_VALID (1<<0) // Aircraft Lat/Lon is known
#define MODES_ACFLAGS_AOG (1<<9) // Aircraft is On the Ground
#define MODES_ACFLAGS_LATLON_REL_OK (1<<15) // Indicates it's OK to do a relative CPR
#define MODES_SBS_LAT_LONG_FRESH (1<<0)
#define MODES_DEBUG_DEMOD (1<<0)
@ -147,7 +151,7 @@ struct aircraft {
char flight[16]; // Flight number
unsigned char signalLevel[8]; // Last 8 Signal Amplitudes
int altitude; // Altitude
int speed; // Velocity computed from EW and NS components
int speed; // Velocity
int track; // Angle of flight
time_t seen; // Time at which the last packet was received
time_t seenLatLon; // Time at which the last lat long was calculated
@ -165,6 +169,7 @@ struct aircraft {
int even_cprlat;
int even_cprlon;
double lat, lon; // Coordinated obtained from CPR encoded data
int bFlags; // Flags related to valid fields in this structure
int sbsflags;
uint64_t odd_cprtime, even_cprtime;
struct aircraft *next; // Next aircraft in our linked list
@ -304,7 +309,9 @@ struct modesMessage {
int modeA; // 13 bits identity (Squawk).
// Fields used by multiple message types.
int altitude, unit;
int altitude;
int unit;
int bFlags; // Flags related to fields in this structure
};
void interactiveShowData(void);
@ -2424,8 +2431,16 @@ void decodeCPR(struct aircraft *a, int fflag, int surface) {
double rlat0 = AirDlat0 * (cprModFunction(j,60) + lat0 / 131072);
double rlat1 = AirDlat1 * (cprModFunction(j,59) + lat1 / 131072);
if (rlat0 >= 270) rlat0 -= 360;
if (rlat1 >= 270) rlat1 -= 360;
if (surface) {
// If we're on the ground, make sure we have our receiver base station Lat/Lon
if (0 == (Modes.bUserFlags & MODES_USER_LATLON_VALID))
{return;}
rlat0 += floor(Modes.fUserLat / 90.0) * 90.0; // Move from 1st quadrant to our quadrant
rlat1 += floor(Modes.fUserLat / 90.0) * 90.0;
} else {
if (rlat0 >= 270) rlat0 -= 360;
if (rlat1 >= 270) rlat1 -= 360;
}
// Check that both are in the same latitude zone, or abort.
if (cprNLFunction(rlat0) != cprNLFunction(rlat1)) return;
@ -2444,10 +2459,16 @@ void decodeCPR(struct aircraft *a, int fflag, int surface) {
a->lon = cprDlonFunction(rlat0, 0, surface) * (cprModFunction(m, ni)+lon0/131072);
a->lat = rlat0;
}
if (a->lon > 180) a->lon -= 360;
if (surface) {
a->lon += floor(Modes.fUserLon / 90.0) * 90.0; // Move from 1st quadrant to our quadrant
} else if (a->lon > 180) {
a->lon -= 360;
}
a->seenLatLon = a->seen;
a->timestampLatLon = a->timestamp;
a->bFlags |= (MODES_ACFLAGS_LATLON_VALID | MODES_ACFLAGS_LATLON_REL_OK);
a->sbsflags |= MODES_SBS_LAT_LONG_FRESH;
}
@ -2469,13 +2490,15 @@ int decodeCPRrelative(struct aircraft *a, int fflag, int surface, double latr, d
double rlon, rlat;
int j,m;
// If not passed a lat/long, we must be using aircraft relative
if ( (latr == 0) && (lonr == 0) ) {
if (a->bFlags & MODES_ACFLAGS_LATLON_REL_OK) { // Ok to try aircraft relative first
latr = a->lat;
lonr = a->lon;
}
if ( (latr == 0) && (lonr == 0) )
} else if (Modes.bUserFlags & MODES_USER_LATLON_VALID) { // Try ground station relative next
latr = Modes.fUserLat;
lonr = Modes.fUserLon;
} else {
return (-1); // Exit with error - can't do relative if we don't have ref.
}
if (fflag) { // odd
AirDlat = (surface ? 90.0 : 360.0) / 59.0;
@ -2495,8 +2518,8 @@ int decodeCPRrelative(struct aircraft *a, int fflag, int surface, double latr, d
// Check to see that answer is reasonable - ie no more than 1/2 cell away
if (fabs(rlat - a->lat) > (AirDlat/2)) {
a->lat = a->lon = 0; // This will cause a quick exit next time if no global has been done
return (-1); // Time to give up - Latitude error
a->bFlags &= ~MODES_ACFLAGS_LATLON_REL_OK; // This will cause a quick exit next time if no global has been done
return (-1); // Time to give up - Latitude error
}
// Compute the Longitude Index "m"
@ -2508,8 +2531,8 @@ int decodeCPRrelative(struct aircraft *a, int fflag, int surface, double latr, d
// Check to see that answer is reasonable - ie no more than 1/2 cell away
if (fabs(rlon - a->lon) > (AirDlon/2)) {
a->lat = a->lon = 0; // This will cause a quick exit next time if no global has been done
return (-1); // Time to give up - Longitude error
a->bFlags &= ~MODES_ACFLAGS_LATLON_REL_OK; // This will cause a quick exit next time if no global has been done
return (-1); // Time to give up - Longitude error
}
a->lat = rlat;
@ -2517,6 +2540,7 @@ int decodeCPRrelative(struct aircraft *a, int fflag, int surface, double latr, d
a->seenLatLon = a->seen;
a->timestampLatLon = a->timestamp;
a->bFlags |= (MODES_ACFLAGS_LATLON_VALID | MODES_ACFLAGS_LATLON_REL_OK);
a->sbsflags |= MODES_SBS_LAT_LONG_FRESH;
return (0);
@ -3167,7 +3191,7 @@ char *aircraftsToJson(int *len) {
speed = (int) (speed * 1.852);
}
if (a->lat != 0 && a->lon != 0) {
if (a->bFlags & MODES_ACFLAGS_LATLON_VALID) {
l = snprintf(p,buflen,
"{\"hex\":\"%06x\", \"flight\":\"%s\", \"lat\":%f, "
"\"lon\":%f, \"altitude\":%d, \"track\":%d, "