Add stats for total aircraft tracks and tracks that have only a single message.

README-json.md

@@ -109,4 +109,9 @@ Each period has the following subkeys:
    * local_ok: local (relative) positions successfully found
    * local_skipped: local (relative) positions not used because we did not have the right data (e.g. position was ambiguous given the receiver range)
    * filtered: number of CPR messages ignored because they matched one of the heuristics for faulty transponder output
+ * tracks: statistics on aircraft tracks. Each track represents a unique aircraft and persists for up to 5 minutes after the last message
+   from the aircraft is heard. If messages from the same aircraft are subsequently heard after the 5 minute period, this will be counted
+   as a new track.
+   * all: total tracks created
+   * single_message: tracks consisting of only a single message. These are usually due to message decoding errors that produce a bad aircraft address.
  * messages: total number of messages accepted by dump1090 from any source

net_io.c

@@ -887,6 +887,8 @@ static char * appendStatsJson(char *p,
                       ",\"local_skipped\":%u"
                       ",\"filtered\":%u}"
                       ",\"cpu\":{\"demod\":%llu,\"reader\":%llu,\"background\":%llu}"
+                      ",\"tracks\":{\"all\":%u"
+                      ",\"single_message\":%u}"
                       ",\"messages\":%u}",
                       st->cpr_global_ok,
                       st->cpr_global_bad,
@@ -897,6 +899,8 @@ static char * appendStatsJson(char *p,
                       (unsigned long long)demod_cpu_millis,
                       (unsigned long long)reader_cpu_millis,
                       (unsigned long long)background_cpu_millis,
+                      st->unique_aircraft,
+                      st->single_message_aircraft,
                       st->messages_total);
     }
 

stats.c

@@ -132,6 +132,9 @@ void display_stats(struct stats *st) {
            st->cpr_local_skipped,
            st->cpr_filtered);
 
+    printf("%u unique aircraft tracks\n", st->unique_aircraft);
+    printf("%u aircraft tracks where only one message was seen\n", st->single_message_aircraft);
+
     if (Modes.net && Modes.net_http_port)
         printf("%d HTTP requests\n", st->http_requests);
 
@@ -150,6 +153,7 @@ void display_stats(struct stats *st) {
                (unsigned long long) background_cpu_millis);
     }
 
+
     fflush(stdout);
 }
 
@@ -224,5 +228,9 @@ void add_stats(const struct stats *st1, const struct stats *st2, struct stats *t
     target->cpr_local_ok = st1->cpr_local_ok + st2->cpr_local_ok;
     target->cpr_local_skipped = st1->cpr_local_skipped + st2->cpr_local_skipped;
     target->cpr_filtered = st1->cpr_filtered + st2->cpr_filtered;
+
+    // aircraft
+    target->unique_aircraft = st1->unique_aircraft + st2->unique_aircraft;
+    target->single_message_aircraft = st1->single_message_aircraft + st2->single_message_aircraft;
 }
 

stats.h

@@ -105,6 +105,12 @@ struct stats {
     unsigned int cpr_local_ok;
     unsigned int cpr_local_skipped;
     unsigned int cpr_filtered;
+
+    // aircraft:
+    // total "new" aircraft (i.e. not seen in the last 30 or 300s)
+    unsigned int unique_aircraft;
+    // we saw only a single message
+    unsigned int single_message_aircraft;
 };    
 
 void add_stats(const struct stats *st1, const struct stats *st2, struct stats *target);

track.c

@@ -84,6 +84,8 @@ struct aircraft *trackCreateAircraft(struct modesMessage *mm) {
     // Copy the first message so we can emit it later when a second message arrives.
     a->first_message = *mm;
 
+    Modes.stats_current.unique_aircraft++;
+
     return (a);
 }
 
@@ -490,6 +492,11 @@ static void trackRemoveStaleAircraft(time_t now)
     while(a) {
         if ((now - a->seen) > TRACK_AIRCRAFT_TTL ||
             (a->messages == 1 && (now - a->seen) > TRACK_AIRCRAFT_ONEHIT_TTL)) {
+            // Count aircraft where we saw only one message before reaping them.
+            // These are likely to be due to messages with bad addresses.
+            if (a->messages == 1)
+                Modes.stats_current.single_message_aircraft++;
+
             // Remove the element from the linked list, with care
             // if we are removing the first element
             if (!prev) {