diff --git a/msg/vehicle_local_position.msg b/msg/vehicle_local_position.msg
index 6f42547e43..9b8bbca3e0 100644
--- a/msg/vehicle_local_position.msg
+++ b/msg/vehicle_local_position.msg
@@ -1,4 +1,5 @@
 # Fused local position in NED.
+# The coordinate system origin is the vehicle position at the time when the EKF2-module was started.
 
 uint64 timestamp			# time since system start (microseconds)
 uint64 timestamp_sample                 # the timestamp of the raw data (microseconds)