Improve global position updating

gradle.properties

@@ -1,5 +1,5 @@
 GROUP=aero.t2s
-VERSION_NAME=0.2.5-SNAPSHOT
+VERSION_NAME=0.2.6-SNAPSHOT
 
 POM_ARTIFACT_ID=mode-s
 POM_NAME=Mode-S/ADS-B (1090Mhz)

src/main/java/aero/t2s/modes/CprPosition.java

@@ -1,10 +1,12 @@
 package aero.t2s.modes;
 
+import java.time.Instant;
+
 public class CprPosition {
  private double lat;
  private double lon;
  private boolean valid;
- private int time;
+ private long time;
 
  public CprPosition() {
  this.lat = 0.0;
@@ -14,9 +16,11 @@ public CprPosition() {
  public CprPosition(double lat, double lon) {
  setLatLon(lat ,lon);
  }
+
  public void setLatLon(double lat, double lon) {
  this.lat = lat;
  this.lon = lon;
+ this.time = Instant.now().toEpochMilli();
  this.valid = true;
  }
 
@@ -36,15 +40,19 @@ public double getLon() {
  return lon;
  }
 
- public void setTime(int time) {
+ public void setTime(long time) {
  this.time = time;
  }
 
- public int getTime() {
+ public long getTime() {
  return time;
  }
 
  public boolean isValid() {
  return valid;
  }
+
+ public boolean isExpired() {
+ return time < Instant.now().minusSeconds(10).toEpochMilli();
+ }
 }

src/main/java/aero/t2s/modes/ModeSHandler.java

@@ -1,6 +1,7 @@
 package aero.t2s.modes;
 
 import aero.t2s.modes.decoder.df.DownlinkFormat;
+import aero.t2s.modes.decoder.df.df17.AirbornePosition;
 
 import java.util.function.Consumer;
 
@@ -42,10 +43,10 @@ protected short[] toData(final String input) throws EmptyMessageException, ModeA
  }
 
  public void start() {
-
+ AirbornePosition.start();
  }
 
  public void stop() {
-
+ AirbornePosition.stop();
  }
 }

src/main/java/aero/t2s/modes/Track.java

@@ -9,9 +9,6 @@ public class Track {
  private String icao;
  private String callsign;
  private Altitude altitude = new Altitude();
- private boolean cprEvenValid = false;
- private CprPosition cprEven = new CprPosition();
- private CprPosition cprOdd = new CprPosition();
  private double lat;
  private double lon;
  private boolean positionAvailable = false;
@@ -199,22 +196,6 @@ public double getLon() {
  return lon;
  }
 
- public CprPosition getCprEven() {
- return cprEven;
- }
-
- public void setCprEven(CprPosition cprEven) {
- this.cprEven = cprEven;
- }
-
- public CprPosition getCprOdd() {
- return cprOdd;
- }
-
- public void setCprOdd(CprPosition cprOdd) {
- this.cprOdd = cprOdd;
- }
-
  public Version getVersion() {
  return version;
  }

src/main/java/aero/t2s/modes/decoder/Decoder.java

@@ -50,7 +50,7 @@ public DownlinkFormat decode(short[] data) throws UnknownDownlinkFormatException
  df = new DF16(data);
  break;
  case 17:
- df = new DF17(data, originLat, originLon);
+ df = new DF17(data);
  break;
  case 18:
  df = new DF18(data);

src/main/java/aero/t2s/modes/decoder/df/DF17.java

@@ -4,15 +4,10 @@
 import aero.t2s.modes.decoder.df.df17.*;
 
 public class DF17 extends DownlinkFormat {
- private final double originLat;
- private final double originLon;
-
  private ExtendedSquitter extendedSquitter;
 
- public DF17(short[] data, double originLat, double originLon) {
+ public DF17(short[] data) {
  super(data, IcaoAddress.FROM_MESSAGE);
- this.originLat = originLat;
- this.originLon = originLon;
  }
 
  @Override
@@ -34,7 +29,7 @@ public DF17 decode() {
  case 20:
  case 21:
  case 22:
- extendedSquitter = new AirbornePosition(data, originLat, originLon);
+ extendedSquitter = new AirbornePosition(data, getIcao());
  break;
  case 1:
  case 2:

src/main/java/aero/t2s/modes/decoder/df/df17/AirbornePosition.java

@@ -3,14 +3,15 @@
 import aero.t2s.modes.Track;
 import aero.t2s.modes.CprPosition;
 import aero.t2s.modes.constants.*;
+import aero.t2s.modes.decoder.Common;
 import aero.t2s.modes.registers.Register05;
 import aero.t2s.modes.registers.Register05V0;
 import aero.t2s.modes.registers.Register05V2;
 
-public class AirbornePosition extends ExtendedSquitter {
- private final double originLat;
- private final double originLon;
+import java.util.*;
 
+public class AirbornePosition extends ExtendedSquitter {
+ private final String address;
  private SurveillanceStatus surveillanceStatus;
  private int singleAntennaFlag;
 
@@ -19,16 +20,14 @@ public class AirbornePosition extends ExtendedSquitter {
 
  private boolean positionAvailable;
 
- private CprPosition cprEven = new CprPosition();
- private CprPosition cprOdd = new CprPosition();
-
  private double lat;
  private double lon;
+ private static Map<String, PositionUpdate> cache = new HashMap<>();
+ private static Timer cacheCleanup;
 
- public AirbornePosition(short[] data, final double originLat, final double originLon) {
+ public AirbornePosition(short[] data, String address) {
  super(data);
- this.originLat = originLat;
- this.originLon = originLon;
+ this.address = address;
  }
 
  @Override
@@ -59,14 +58,38 @@ public AirbornePosition decode() {
  cprLon = cprLon | (data[9] << 8);
  cprLon = cprLon | data[10];
 
+
+ if (!cache.containsKey(address)) {
+ if (!isCprEven) {
+ return this;
+ }
+
+ synchronized (cache) {
+ cache.putIfAbsent(address, new PositionUpdate(
+ new CprPosition(cprLat / (double)(1 << 17), cprLon / (double)(1 << 17))
+ ));
+ }
+ }
+
+ PositionUpdate positionUpdate;
+ synchronized (cache) {
+ positionUpdate = cache.get(address);
+ }
  if (isCprEven) {
- this.cprEven.setLatLon(cprLat/(double)(1 << 17), cprLon/(double)(1 << 17));
+ positionUpdate.setEven(new CprPosition(cprLat / (double) (1 << 17), cprLon / (double) (1 << 17)));
+ } else {
+ positionUpdate.setOdd(new CprPosition(cprLat, cprLon));
  }
- else {
- this.cprOdd.setLatLon(cprLat, cprLon);
+
+ if (positionUpdate.isComplete()) {
+ calculateGlobal(positionUpdate.even, positionUpdate.odd);
+ } else if (positionUpdate.isPreviousPositionAvailable() && positionUpdate.isPreviousPositionAvailable()) {
+ calculateLocal(positionUpdate.odd, true, positionUpdate.previousLat, positionUpdate.previousLon);
  }
 
- calculatePosition(isCprEven);
+ if (positionAvailable) {
+ positionUpdate.setPreviousPosition(this.lat, this.lon);
+ }
 
  return this;
  }
@@ -77,9 +100,9 @@ public void apply(Track track) {
  track.setSpi(surveillanceStatus == SurveillanceStatus.SPI);
  track.setTempAlert(surveillanceStatus == SurveillanceStatus.TEMPORARY_ALERT);
  track.setEmergency(surveillanceStatus == SurveillanceStatus.PERMANENT_ALERT);
- track.setCprEven(cprEven);
- track.setCprOdd(cprOdd);
- track.setLatLon(lat, lon);
+ if (positionAvailable) {
+  track.setLatLon(lat, lon);
+ }
 
  if (versionChanged(track)) {
  switch (track.getVersion()) {
@@ -130,14 +153,6 @@ public BarometricAltitudeIntegrityCode getNICbaro() {
  }
  }
 
- public double getOriginLat() {
- return originLat;
- }
-
- public double getOriginLon() {
- return originLon;
- }
-
  public SurveillanceStatus getSurveillanceStatus() {
  return surveillanceStatus;
  }
@@ -215,25 +230,6 @@ private AltitudeSource determineAltitudeSource() {
  return AltitudeSource.GNSS_HAE;
  }
 
- private void calculatePosition(boolean isEven) {
- if (!positionAvailable) {
- //TODO Could be other cases where we need to do global calculation, such as too much time elapsed since last position update
- calculateGlobal(cprEven, cprOdd);
- positionAvailable = true;
- }
- else {
- if (isEven) {
- if (cprOdd.isValid()) {
- calculateLocal(cprEven, false, this.lat, this.lon);
- }
- } else {
- if (cprEven.isValid()) {
- calculateLocal(cprOdd, true, this.lat, this.lon);
- }
- }
- }
- }
-
  private void calculateLocal(CprPosition cpr, boolean isOdd, double previousLat, double previousLon) {
 
  double dlat = isOdd ? 360.0 / 59.0 : 360.0 / 60.0;
@@ -298,6 +294,7 @@ private void calculateGlobal(CprPosition cprEven, CprPosition cprOdd) {
  //TODO Should be a sanity-check here to make sure the calculated position isn't outside receiver origin range,
  this.lat = lat;
  this.lon = lon;
+ this.positionAvailable = true;
  }
  private double cprN(double lat, double isOdd) {
  double nl = NL(lat) - isOdd;
@@ -323,4 +320,66 @@ private int calculateAltitude(short[] data, int typeCode) {
 
  return (n * qBit) - 1000;
  }
+
+ public static void start() {
+ AirbornePosition.cache.clear();
+ AirbornePosition.cacheCleanup.schedule(new TimerTask() {
+ @Override
+ public void run() {
+ List<String> expired = new LinkedList<>();
+
+ synchronized (cache) {
+ cache.entrySet().stream().filter(entry -> entry.getValue().isExpired()).forEach(entry -> expired.add(entry.getKey()));
+ expired.forEach(cache::remove);
+ }
+ }
+ }, 0, 10_000);
+ }
+
+ public static void stop() {
+ AirbornePosition.cacheCleanup.cancel();
+ AirbornePosition.cacheCleanup = null;
+
+ AirbornePosition.cache.clear();
+ }
+
+ class PositionUpdate {
+ private CprPosition even;
+ private CprPosition odd;
+
+
+ private boolean previousPositionAvailable = false;
+ private double previousLat;
+ private double previousLon;
+
+ public PositionUpdate(CprPosition even) {
+ this.even = even;
+ }
+
+ public void setEven(CprPosition even) {
+ this.even = even;
+ this.odd = null;
+ }
+
+ public void setOdd(CprPosition odd) {
+ this.odd = odd;
+ }
+
+ public void setPreviousPosition(double lat, double lon) {
+ this.previousLat = lat;
+ this.previousLon = lon;
+ }
+
+ public boolean isPreviousPositionAvailable() {
+ return this.previousPositionAvailable;
+ }
+
+ public boolean isComplete() {
+ return even != null && odd != null;
+ }
+
+ public boolean isExpired() {
+ return even.isExpired() || odd.isExpired();
+ }
+ }
 }