feat: extract_mcap — /navigation/altitude (Kogger) -> HDF5 altitude_m + seafloor_depth_m

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/test_extract_mcap.py

@@ -22,3 +22,41 @@ def test_write_auv_mcap_group():
             assert list(f["auv_mcap/t_ns"][:]) == list(t)
     finally:
         os.unlink(path)
+
+
+def test_write_auv_mcap_group_with_altitude():
+    from extract.extract_mcap import write_auv_mcap_group
+    t     = np.array([1000, 2000, 3000], dtype=np.int64)
+    lat   = np.array([43.1, 43.2, 43.3])
+    lon   = np.array([5.6, 5.61, 5.62])
+    depth = np.array([5.0, 5.5, 6.0])
+    alt   = np.array([1.2, 1.3, 1.1])
+
+    with tempfile.NamedTemporaryFile(suffix=".h5", delete=False) as tmp:
+        path = tmp.name
+    try:
+        write_auv_mcap_group(path, t, lat, lon, depth, alt)
+        with h5py.File(path, "r") as f:
+            assert "altitude_m" in f["auv_mcap"]
+            assert "seafloor_depth_m" in f["auv_mcap"]
+            assert np.allclose(f["auv_mcap/altitude_m"][:], alt)
+            assert np.allclose(f["auv_mcap/seafloor_depth_m"][:], depth + alt)
+    finally:
+        os.unlink(path)
+
+
+def test_write_auv_mcap_group_without_altitude():
+    from extract.extract_mcap import write_auv_mcap_group
+    t     = np.array([1000, 2000], dtype=np.int64)
+    lat   = np.zeros(2)
+    lon   = np.zeros(2)
+    depth = np.array([3.0, 4.0])
+
+    with tempfile.NamedTemporaryFile(suffix=".h5", delete=False) as tmp:
+        path = tmp.name
+    try:
+        write_auv_mcap_group(path, t, lat, lon, depth, altitude_m=None)
+        with h5py.File(path, "r") as f:
+            assert "altitude_m" not in f["auv_mcap"]
+    finally:
+        os.unlink(path)