User Lat/Lon setting

Based on initial code supplied by VK1ET

Allow the user to specify their receivers (technically their aerials)
physical location. This is required for decoding ground positions, and
also for uploading aircraft data to various sharer sites.

The position can be hardwired by setting the MODES_USER_LATITUDE_DFLT
and MODES_USER_LONGITUDE_DFLT constants before compilation, or entered
at runtime via the new command line switches --lat and --lon.   Either
way, the values are checked for validity before use.

dump1090.c

@@ -56,7 +56,9 @@
 // MinorVer changes when additional features are added, but not for bug fixes (range 00-99)
 // DayDate & Year changes for all changes, including for bug fixes. It represent the release date of the update
 //
-#define MODES_DUMP1090_VERSION     "1.04.0805.13"
+#define MODES_DUMP1090_VERSION     "1.04.0905.13"
+#define MODES_USER_LATITUDE_DFLT   (0.0)
+#define MODES_USER_LONGITUDE_DFLT  (0.0)
 
 #define MODES_DEFAULT_RATE         2000000
 #define MODES_DEFAULT_FREQ         1090000000
@@ -101,6 +103,8 @@
 #define MODES_UNIT_FEET 0
 #define MODES_UNIT_METERS 1
 
+#define MODES_USER_LATLON_VALID (1<<0)
+
 #define MODES_SBS_LAT_LONG_FRESH (1<<0)
 
 #define MODES_DEBUG_DEMOD (1<<0)
@@ -230,6 +234,11 @@ struct {
     int mlat;                       /* Use Beast ascii format for raw data output, i.e. @...; iso *...; */
     int interactive_rtl1090;        /* flight table in interactive mode is formatted like RTL1090 */
 
+    // User details
+    double fUserLat;                // Users receiver/antenna lat/lon needed for initial surface location
+    double fUserLon;                // Users receiver/antenna lat/lon needed for initial surface location
+    int    bUserFlags;              // Flags relating to the user details
+
     /* Interactive mode */
     struct aircraft *aircrafts;
     uint64_t interactive_last_update;  /* Last screen update in milliseconds */
@@ -342,6 +351,8 @@ void modesInitConfig(void) {
     Modes.net_http_port       = MODES_NET_HTTP_PORT;
     Modes.interactive_rows    = MODES_INTERACTIVE_ROWS;
     Modes.interactive_ttl     = MODES_INTERACTIVE_TTL;
+    Modes.fUserLat            = MODES_USER_LATITUDE_DFLT;
+    Modes.fUserLon            = MODES_USER_LONGITUDE_DFLT;
 }
 
 void modesInit(void) {
@@ -366,6 +377,25 @@ void modesInit(void) {
     memset(Modes.data,       127, MODES_ASYNC_BUF_SIZE);
     memset(Modes.magnitude,  0,   MODES_ASYNC_BUF_SIZE+MODES_PREAMBLE_SIZE+MODES_LONG_MSG_SIZE);
 
+    // Validate the users Lat/Lon home location inputs
+    if ( (Modes.fUserLat >   90.0)  // Latitude must be -90 to +90
+      || (Modes.fUserLat <  -90.0)  // and 
+      || (Modes.fUserLon >  360.0)  // Longitude must be -180 to +360
+      || (Modes.fUserLon < -180.0) ) {
+        Modes.fUserLat = Modes.fUserLon = 0.0;
+    } else if (Modes.fUserLon > 180.0) { // If Longitude is +180 to +360, make it -180 to 0
+        Modes.fUserLon -= 360.0;
+    }
+    // If both Lat and Lon are 0.0 then the users location is either invalid/not-set, or (s)he's in the 
+    // Atlantic ocean off the west coast of Africa. This is unlikely to be correct. 
+    // Set the user LatLon valid flag only if either Lat or Lon are non zero. Note the Greenwich meridian 
+    // is at 0.0 Lon,so we must check for either fLat or fLon being non zero not both. 
+    // Testing the flag at runtime will be much quicker than ((fLon != 0.0) || (fLat != 0.0))
+    Modes.bUserFlags &= ~MODES_USER_LATLON_VALID;
+    if ((Modes.fUserLat != 0.0) || (Modes.fUserLon != 0.0)) {
+        Modes.bUserFlags |= MODES_USER_LATLON_VALID;
+    }
+
     // Limit the maximum requested raw output size to less than one Ethernet Block 
     if (Modes.net_output_raw_size > (MODES_RAWOUT_BUF_FLUSH))
       {Modes.net_output_raw_size = MODES_RAWOUT_BUF_FLUSH;}
@@ -1859,7 +1889,7 @@ void detectModeS(uint16_t *m, uint32_t mlen) {
             if (Modes.mode_ac) 
                 {
                 struct modesMessage mm;
-                int ModeA = detectModeA(pPreamble, &mm); 
+                int ModeA = detectModeA(pPreamble, &mm);
 
                 if (ModeA) // We have found a valid ModeA/C in the data                    
                     {
@@ -3377,6 +3407,8 @@ void showHelp(void) {
 "--net-ri-port <port>     TCP raw input listen port  (default: 30001)\n"
 "--net-http-port <port>   HTTP server port (default: 8080)\n"
 "--net-sbs-port <port>    TCP BaseStation output listen port (default: 30003)\n"
+"--lat <latitude>         Reference/receiver latitide for surface posn (opt)\n"
+"--lon <longitude>        Reference/receiver longitude for surface posn (opt)\n"
 "--fix                    Enable single-bits error correction using CRC\n"
 "--no-fix                 Disable single-bits error correction using CRC\n"
 "--no-crc-check           Disable messages with broken CRC (discouraged)\n"
@@ -3490,10 +3522,14 @@ int main(int argc, char **argv) {
             Modes.fix_errors = 1;
         } else if (!strcmp(argv[j],"--interactive")) {
             Modes.interactive = 1;
-        } else if (!strcmp(argv[j],"--interactive-rows")) {
+        } else if (!strcmp(argv[j],"--interactive-rows") && more) {
             Modes.interactive_rows = atoi(argv[++j]);
-        } else if (!strcmp(argv[j],"--interactive-ttl")) {
+        } else if (!strcmp(argv[j],"--interactive-ttl") && more) {
             Modes.interactive_ttl = atoi(argv[++j]);
+        } else if (!strcmp(argv[j],"--lat") && more) {
+            Modes.fUserLat = atof(argv[++j]);
+        } else if (!strcmp(argv[j],"--lon") && more) {
+            Modes.fUserLon = atof(argv[++j]);
         } else if (!strcmp(argv[j],"--debug") && more) {
             char *f = argv[++j];
             while(*f) {