[radar] Add --filter_time to reduce mis-decode

Add --filter_time for removing airplanes after the the specified time.
This is down to 2 seconds in the ICAO document, but I see 10 seconds as
being pretty good for reducing the amount of mis-decodes greatly.

This was previosuly 60 seconds, which was giving very bad lat/long if a
long period of time was between both messages odd/even.

See #21

apps/README.md

@@ -36,17 +36,19 @@ USAGE:
     radar [OPTIONS] --lat <LAT> --long <LONG>
 
 OPTIONS:
-        --cities <CITIES>...    Vector of cities [(name, lat, long),..]
-        --disable-lat-long      Disable output of latitude and longitude on display
-        --gpsd                  Enable automatic updating of lat/lon from gpsd
-        --gpsd-ip <GPSD_IP>     Ip address of gpsd [default: localhost]
-    -h, --help                  Print help information
-        --host <HOST>           [default: localhost]
-        --lat <LAT>             Antenna location latitude
-        --long <LONG>           Antenna location longitude
-        --port <PORT>           [default: 30002]
-        --scale <SCALE>         Zoom level of Radar and Coverage [default: 1.2]
-    -V, --version               Print version information
+        --cities <CITIES>...           Vector of cities [(name, lat, long),..]
+        --disable-lat-long             Disable output of latitude and longitude on display
+        --filter-time <FILTER_TIME>    Seconds since last message from airplane, triggers removal of
+                                       airplane after time is up [default: 10]
+        --gpsd                         Enable automatic updating of lat/lon from gpsd
+        --gpsd-ip <GPSD_IP>            Ip address of gpsd [default: localhost]
+    -h, --help                         Print help information
+        --host <HOST>                  [default: localhost]
+        --lat <LAT>                    Antenna location latitude
+        --long <LONG>                  Antenna location longitude
+        --port <PORT>                  [default: 30002]
+        --scale <SCALE>                Zoom level of Radar and Coverage [default: 1.2]
+    -V, --version                      Print version information
 ```
 
 ### Key Bindings

apps/src/lib.rs

@@ -36,15 +36,12 @@ impl Default for AirplaneState {
 pub struct AirplaneCoor {
     /// [odd, even]
     pub altitudes: [Option<Altitude>; 2],
-    /// last time of frame Rx
-    pub last_time: SystemTime,
 }
 
 impl Default for AirplaneCoor {
     fn default() -> Self {
         Self {
             altitudes: [None, None],
-            last_time: SystemTime::now(),
         }
     }
 }
@@ -96,18 +93,15 @@ impl Airplanes {
     /// Add `Altitude` from adsb frame
     pub fn add_altitude(&mut self, icao: ICAO, altitude: &Altitude) {
         let state = self.0.entry(icao).or_insert_with(AirplaneState::default);
-        let now = SystemTime::now();
         match altitude.odd_flag {
             CPRFormat::Odd => {
                 state.coords = AirplaneCoor {
                     altitudes: [state.coords.altitudes[0], Some(*altitude)],
-                    last_time: now,
                 };
             },
             CPRFormat::Even => {
                 state.coords = AirplaneCoor {
                     altitudes: [Some(*altitude), state.coords.altitudes[1]],
-                    last_time: now,
                 };
             },
         }
@@ -149,8 +143,9 @@ impl Airplanes {
     }
 
     /// Remove airplane after not active for a time
-    pub fn prune(&mut self) {
-        self.0
-            .retain(|_, v| v.last_time.elapsed().unwrap() < std::time::Duration::from_secs(60));
+    pub fn prune(&mut self, filter_time: u64) {
+        self.0.retain(|_, v| {
+            v.last_time.elapsed().unwrap() < std::time::Duration::from_secs(filter_time)
+        });
     }
 }

apps/src/radar.rs

@@ -109,6 +109,9 @@ struct Opts {
     /// Ip address of gpsd
     #[clap(long, default_value = "localhost")]
     gpsd_ip: String,
+    /// Seconds since last message from airplane, triggers removal of airplane after time is up
+    #[clap(long, default_value = "10")]
+    filter_time: u64,
 }
 
 #[derive(Copy, Clone)]
@@ -197,6 +200,7 @@ fn main() {
     let mut quit = None;
     let original_scale = opts.scale;
     let mut airplanes_state = TableState::default();
+    let filter_time = opts.filter_time;
 
     let mut settings = Settings {
         scale: opts.scale,
@@ -277,7 +281,7 @@ fn main() {
 
         input.clear();
         // remove airplanes that timed-out
-        adsb_airplanes.prune();
+        adsb_airplanes.prune(filter_time);
 
         // tui drawing
         terminal