Check BDS50 on out of range values

terminal2 · Oct 16, 2022 · 0333236 · 0333236
1 parent f87ebbd
commit 0333236
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Showing 2 changed files with 57 additions and 16 deletions.
diff --git a/src/main/java/aero/t2s/modes/decoder/df/bds/Bds50.java b/src/main/java/aero/t2s/modes/decoder/df/bds/Bds50.java
@@ -204,22 +204,13 @@ public Bds50(short[] data) {
  return;
  }
 
- // If known check if roll angle & track angle rate matches expected / value
- // Formula from SkyBrary TurnRate (1) = (TAS / 10) => Roll Angle
- // Which we can rewrite to Roll Angle * 10 * Turn Rate = TAS
- // When TAS is not known we can use GS instead allow for bigger margin
- if (statusTrackAngle && statusRollAngle && trackAngleRate != 0) {
- double expectedTAS = Math.abs(rollAngle * 10d * (trackAngleRate / 3d));
- if (statusTas) {
- if (Math.abs(expectedTAS - tas) > 50) {
- invalidate();
- return;
- }
- } else if (statusGs) {
- if (Math.abs(expectedTAS - gs) > 150) {
- invalidate();
- return;
- }
+ // Check if values are way off th scale.
+ // We can only check large values
+ if ((statusTas || statusGs) && statusTrackAngle && statusRollAngle && Math.abs(trackAngleRate) > 0.25 && Math.abs(rollAngle) > 5) {
+ // We cannot have a rate one turn at 180 knots or greater at less than 30 degrees of bank
+ if ((gs > 180 || tas > 180) && rollAngle < 30 && trackAngleRate > 3) {
+ invalidate();
+ return;
  }
  }
  }

diff --git a/src/test/java/aero/t2s/modes/decoder/df/DfRealMessageTest.java b/src/test/java/aero/t2s/modes/decoder/df/DfRealMessageTest.java
@@ -289,6 +289,56 @@ public void test_df21_bds50_485209() throws UnknownDownlinkFormatException {
  assertEquals(31.8, bds.getTrueTrack(), 0.1);
  }
 
+ @Test
+ public void test_df21_bds50_484FDF() throws UnknownDownlinkFormatException {
+ DownlinkFormat df = testMessage("A800080080502D2A600CA9DF5877");
+
+ assertInstanceOf(DF21.class, df);
+ DF21 df21 = (DF21) df;
+ assertEquals("484FDF", df.getIcao()); // Military / corrupt transponder
+ assertEquals(1000, df21.getModeA());
+
+ assertTrue(df21.isValid());
+ assertInstanceOf(Bds50.class, df21.getBds());
+
+ Bds50 bds = (Bds50) df21.getBds();
+ assertTrue(bds.isStatusGs());
+ assertEquals(338, bds.getGs(), 0.1);
+ assertTrue(bds.isStatusTas());
+ assertEquals(338, bds.getTas(), 0.1);
+ assertTrue(bds.isStatusRollAngle());
+ assertEquals(0.35, bds.getRollAngle(), 0.1);
+ assertTrue(bds.isStatusTrueAngleRate());
+ assertEquals(0, bds.getTrackAngleRate(), 0.1);
+ assertTrue(bds.isStatusTrackAngle());
+ assertEquals(3.8, bds.getTrueTrack(), 0.1);
+ }
+
+ @Test
+ public void test_df20_bds50_48418A() throws UnknownDownlinkFormatException {
+ DownlinkFormat df = testMessage("A0000E978F1FBD316114BDA0FFBF");
+
+ assertInstanceOf(DF20.class, df);
+ DF20 df20 = (DF20) df;
+ assertEquals("48418A", df.getIcao()); // Military / corrupt transponder
+ assertEquals(22375, df20.getAltitude().getAltitude());
+
+ assertTrue(df20.isValid());
+ assertInstanceOf(Bds50.class, df20.getBds());
+
+ Bds50 bds = (Bds50) df20.getBds();
+ assertTrue(bds.isStatusGs());
+ assertEquals(394, bds.getGs(), 0.1);
+ assertTrue(bds.isStatusTas());
+ assertEquals(378, bds.getTas(), 0.1);
+ assertTrue(bds.isStatusRollAngle());
+ assertEquals(21, bds.getRollAngle(), 0.1);
+ assertTrue(bds.isStatusTrueAngleRate());
+ assertEquals(1, bds.getTrackAngleRate(), 0.1);
+ assertTrue(bds.isStatusTrackAngle());
+ assertEquals(354, bds.getTrueTrack(), 0.1);
+ }
+
 
  private DownlinkFormat testMessage(String message) throws UnknownDownlinkFormatException {
  Decoder decoder = new Decoder(new HashMap<>(), 50, 2, ModeSDatabase.createDatabase());