Fix Altitude decoding

terminal2 · Oct 12, 2022 · c6daacd · c6daacd
1 parent c54c450
commit c6daacd
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Showing 3 changed files with 4 additions and 3 deletions.
diff --git a/src/main/java/aero/t2s/modes/decoder/AltitudeEncoding.java b/src/main/java/aero/t2s/modes/decoder/AltitudeEncoding.java
@@ -23,7 +23,8 @@ public static Altitude decode(int encoded) {
  }
 
  private static Altitude decodeFeet(int encoded) {
- int n = ((encoded & 0b1111110000000) >>> 2) | (encoded & 0b11111);
+ // Remove bits 7 & 8 and stitch the binary message together.
+ int n = ((encoded & 0b1111110000000) >>> 2) + ((encoded & 0b100000) >>> 1) + (encoded & 0b1111);
 
  int altitude = (25 * n) - 1000;
 

diff --git a/src/test/java/aero/t2s/modes/decoder/df/DF0Test.java b/src/test/java/aero/t2s/modes/decoder/df/DF0Test.java
@@ -51,7 +51,7 @@ void it_decodes_altitude()
  {
  df0 = new DF0(BinaryHelper.stringToByteArray("02E1951DE7596A")).decode();
 
- assertEquals(33325, df0.getAltitude().getAltitude(), 0.1);
+ assertEquals(32925, df0.getAltitude().getAltitude(), 0.1);
  assertEquals(25, df0.getAltitude().getStep());
  assertFalse(df0.getAltitude().isMetric());
  }

diff --git a/src/test/java/aero/t2s/modes/decoder/df/DfRealMessageTest.java b/src/test/java/aero/t2s/modes/decoder/df/DfRealMessageTest.java
@@ -73,7 +73,7 @@ public void test_df20_bds60_800736() throws UnknownDownlinkFormatException {
  assertInstanceOf(DF20.class, df);
  DF20 df20 = (DF20) df;
  assertEquals("800736", df.getIcao());
- assertEquals(41375, df20.getAltitude().getAltitude());
+ assertEquals(40975, df20.getAltitude().getAltitude());
 
  assertTrue(df20.isValid());
  assertInstanceOf(Bds60.class, df20.getBds());