diff --git a/.gitignore b/.gitignore
index 68d6eaa..453dfd0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -58,3 +58,9 @@ target/
 
 # PyCharm
 .idea/
+
+# Environments
+.env
+.venv
+env/
+venv/
diff --git a/README.rst b/README.rst
index 0df40d2..ec7d2ed 100644
--- a/README.rst
+++ b/README.rst
@@ -165,6 +165,7 @@ Core functions for ADS-B decoding
   pms.adsb.position(msg_even, msg_odd, t_even, t_odd, lat_ref=None, lon_ref=None)
   pms.adsb.airborne_position(msg_even, msg_odd, t_even, t_odd)
   pms.adsb.surface_position(msg_even, msg_odd, t_even, t_odd, lat_ref, lon_ref)
+  pms.adsb.surface_velocity(msg)
 
   pms.adsb.position_with_ref(msg, lat_ref, lon_ref)
   pms.adsb.airborne_position_with_ref(msg, lat_ref, lon_ref)
@@ -175,7 +176,6 @@ Core functions for ADS-B decoding
   # Typecode: 19
   pms.adsb.velocity(msg)          # Handles both surface & airborne messages
   pms.adsb.speed_heading(msg)     # Handles both surface & airborne messages
-  pms.adsb.surface_velocity(msg)
   pms.adsb.airborne_velocity(msg)
 
 
diff --git a/pyModeS/decoder/bds/bds06.py b/pyModeS/decoder/bds/bds06.py
index 998522d..ae7e330 100644
--- a/pyModeS/decoder/bds/bds06.py
+++ b/pyModeS/decoder/bds/bds06.py
@@ -89,6 +89,9 @@ def surface_position(msg0, msg1, t0, t1, lat_ref, lon_ref):
     # four possible longitude solutions
     lons = [lon, lon + 90.0, lon + 180.0, lon + 270.0]
 
+    # make sure lons are between -180 and 180
+    lons = [(l + 180) % 360 - 180 for l in lons]
+
     # the closest solution to receiver is the correct one
     dls = [abs(lon_ref - l) for l in lons]
     imin = min(range(4), key=dls.__getitem__)
diff --git a/tests/test_bds_inference.py b/tests/test_bds_inference.py
index 7d5168c..5ef67f0 100644
--- a/tests/test_bds_inference.py
+++ b/tests/test_bds_inference.py
@@ -19,3 +19,18 @@ def test_bds_is50or60():
     assert bds.is50or60("A0001838201584F23468207CDFA5", 0, 0, 0) == None
     assert bds.is50or60("A0000000FFDA9517000464000000", 182, 237, 1250) == "BDS50"
     assert bds.is50or60("A0000000919A5927E23444000000", 413, 54, 18700) == "BDS60"
+
+
+def test_surface_position():
+    msg0 = "8FE48C033A9FA184B934E744C6FD"
+    msg1 = "8FE48C033A9FA68F7C3D39B1C2F0"
+
+    t0 = 1565608663102
+    t1 = 1565608666214
+
+    lat_ref = -23.4265448
+    lon_ref = -46.4816258
+
+    lat, lon = bds.bds06.surface_position(msg0, msg1, t0, t1, lat_ref, lon_ref)
+
+    assert abs(lon_ref - lon) < 0.05