write gpsd_in altitude to receiver.json

json_out.c

@@ -1877,6 +1877,11 @@ struct char_buffer generateReceiverJson() {
  "\"lon\": %.6f",
  Modes.fUserLat, Modes.fUserLon); // exact location
  }
+ if (Modes.fUserAlt > -1e6) {
+ p = safe_snprintf(p, end,
+ ", \"alt_m_amsl\": %.0f",
+ Modes.fUserAlt);
+ }
  }
 
  p = safe_snprintf(p, end, ", \"jaeroTimeout\": %.1f", ((double) Modes.trackExpireJaero) / (60 * SECONDS));

net_io.c

@@ -3589,6 +3589,7 @@ static int handle_gpsd(struct client *c, char *p, int remote, int64_t now, struc
  // filter all messages which don't have lat / lon
  char *latp = strstr(p, "\"lat\":");
  char *lonp = strstr(p, "\"lon\":");
+ char *altp = strstr(p, "\"alt\":");
  if (!latp || !lonp) {
  if (Modes.debug_gps) {
  fprintf(stderr, "gpsdebug: lat / lon not present: ignoring message.\n");
@@ -3600,13 +3601,26 @@ static int handle_gpsd(struct client *c, char *p, int remote, int64_t now, struc
 
  char *saveptr = NULL;
  strtok_r(latp, ",", &saveptr);
+ saveptr = NULL;
  strtok_r(lonp, ",", &saveptr);
 
  double lat = strtod(latp, NULL);
  double lon = strtod(lonp, NULL);
 
+ double alt_m = -2e6;
+ if (altp) {
+ altp += 6;
+ saveptr = NULL;
+ strtok_r(altp, ",", &saveptr);
+ alt_m = strtod(altp, NULL);
+ }
+
  if (Modes.debug_gps) {
- fprintf(stderr, "gpsdebug: parsed lat,lon: %11.6f,%11.6f\n", lat, lon);
+ if (alt_m > -1e6) {
+ fprintf(stderr, "gpsdebug: parsed lat,lon: %11.6f,%11.6f (alt: %.0f m)\n", lat, lon, alt_m);
+ } else {
+ fprintf(stderr, "gpsdebug: parsed lat,lon: %11.6f,%11.6f (no alt)\n", lat, lon);
+ }
  }
  //fprintf(stderr, "%11.6f %11.6f\n", lat, lon);
 
@@ -3630,6 +3644,9 @@ static int handle_gpsd(struct client *c, char *p, int remote, int64_t now, struc
 
  Modes.fUserLat = lat;
  Modes.fUserLon = lon;
+ if (alt_m > -1e6) {
+ Modes.fUserAlt = alt_m;
+ }
  Modes.userLocationValid = 1;
 
  if (Modes.json_dir) {

readsb.c

@@ -166,6 +166,8 @@ static void configSetDefaults(void) {
  Modes.acasFD2 = -1; // set to -1 so it's clear we don't have that fd
  Modes.sbsOverrideSquawk = -1;
 
+ Modes.fUserAlt = -2e6;
+
  Modes.enable_zstd = 1;
 
  Modes.currentTask = "unset";

readsb.h

@@ -743,6 +743,7 @@ struct _Modes
  int32_t net_output_flush_interval_beast_reduce; // Maximum interval (in milliseconds) between outputwrites
  double fUserLat; // Users receiver/antenna lat/lon needed for initial surface location
  double fUserLon; // Users receiver/antenna lat/lon needed for initial surface location
+ double fUserAlt; // receiver altitude AMSL in meters
  double maxRange; // Absolute maximum decoding range, in *metres*
  char *latString;
  char *lonString;