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Merge pull request #42 from mutability/prefer-global-cpr

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Prefer to use global CPR decoding where possible.
This commit is contained in:
MalcolmRobb 2014-10-02 21:05:26 +01:00
parent bc496fbcad 661246d347
commit 16a900c667
3 changed files with 24 additions and 22 deletions
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2
dump1090.h
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@ -436,7 +436,7 @@ void decodeModesMessage (struct modesMessage *mm, unsigned char *msg);
void displayModesMessage(struct modesMessage *mm);
void useModesMessage (struct modesMessage *mm);
void computeMagnitudeVector(uint16_t *pData);
void decodeCPR (struct aircraft *a, int fflag, int surface);
int decodeCPR (struct aircraft *a, int fflag, int surface);
int decodeCPRrelative (struct aircraft *a, int fflag, int surface);
void modesInitErrorInfo ();
//

21
interactive.c
View file

@ -343,6 +343,7 @@ struct aircraft *interactiveReceiveData(struct modesMessage *mm) {
// If we've got a new cprlat or cprlon
if (mm->bFlags & MODES_ACFLAGS_LLEITHER_VALID) {
int location_ok = 0;
if (mm->bFlags & MODES_ACFLAGS_LLODD_VALID) {
a->odd_cprlat = mm->raw_latitude;
@ -354,25 +355,25 @@ struct aircraft *interactiveReceiveData(struct modesMessage *mm) {
a->even_cprtime = mstime();
}
if (((mm->bFlags | a->bFlags) & MODES_ACFLAGS_LLEITHER_VALID) == MODES_ACFLAGS_LLBOTH_VALID) {
// If we now have both even and odd, decode the CPR
// Try relative CPR first
if (decodeCPRrelative(a, (mm->bFlags & MODES_ACFLAGS_LLODD_VALID), (mm->bFlags & MODES_ACFLAGS_AOG))) {
// If relative CPR fails then try global if the two data are less than 10 seconds apart
if (abs((int)(a->even_cprtime - a->odd_cprtime)) <= 10000) {
decodeCPR(a, (mm->bFlags & MODES_ACFLAGS_LLODD_VALID), (mm->bFlags & MODES_ACFLAGS_AOG));
// If we have enough recent data, try global CPR
if (((mm->bFlags | a->bFlags) & MODES_ACFLAGS_LLEITHER_VALID) == MODES_ACFLAGS_LLBOTH_VALID && abs((int)(a->even_cprtime - a->odd_cprtime)) <= 10000) {
if (decodeCPR(a, (mm->bFlags & MODES_ACFLAGS_LLODD_VALID), (mm->bFlags & MODES_ACFLAGS_AOG)) == 0) {
location_ok = 1;
}
}
// Otherwise try relative CPR.
if (!location_ok && decodeCPRrelative(a, (mm->bFlags & MODES_ACFLAGS_LLODD_VALID), (mm->bFlags & MODES_ACFLAGS_AOG)) == 0) {
location_ok = 1;
}
//If we sucessfully decoded, back copy the results to mm so that we can print them in list output
if (a->bFlags & MODES_ACFLAGS_LATLON_VALID) {
if (location_ok) {
mm->bFlags |= MODES_ACFLAGS_LATLON_VALID;
mm->fLat = a->lat;
mm->fLon = a->lon;
}
}
}
// Update the aircrafts a->bFlags to reflect the newly received mm->bFlags;
a->bFlags |= mm->bFlags;

13
mode_s.c
View file

@ -2014,11 +2014,8 @@ double cprDlonFunction(double lat, int fflag, int surface) {
//
// A few remarks:
// 1) 131072 is 2^17 since CPR latitude and longitude are encoded in 17 bits.
// 2) We assume that we always received the odd packet as last packet for
// simplicity. This may provide a position that is less fresh of a few
// seconds.
//
void decodeCPR(struct aircraft *a, int fflag, int surface) {
int decodeCPR(struct aircraft *a, int fflag, int surface) {
double AirDlat0 = (surface ? 90.0 : 360.0) / 60.0;
double AirDlat1 = (surface ? 90.0 : 360.0) / 59.0;
double lat0 = a->even_cprlat;
@ -2044,7 +2041,8 @@ void decodeCPR(struct aircraft *a, int fflag, int surface) {
surface_rlat = Modes.fUserLat;
surface_rlon = Modes.fUserLon;
} else {
return;
// 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;
@ -2057,7 +2055,8 @@ void decodeCPR(struct aircraft *a, int fflag, int surface) {
if (rlat0 < -90 || rlat0 > 90 || rlat1 < -90 || rlat1 > 90) return;
// Check that both are in the same latitude zone, or abort.
if (cprNLFunction(rlat0) != cprNLFunction(rlat1)) return;
if (cprNLFunction(rlat0) != cprNLFunction(rlat1))
return (-1);
// Compute ni and the Longitude Index "m"
if (fflag) { // Use odd packet.
@ -2083,6 +2082,8 @@ void decodeCPR(struct aircraft *a, int fflag, int surface) {
a->seenLatLon = a->seen;
a->timestampLatLon = a->timestamp;
a->bFlags |= (MODES_ACFLAGS_LATLON_VALID | MODES_ACFLAGS_LATLON_REL_OK);
return 0;
}
//
//=========================================================================