diff --git a/message_definitions/v1.0/ardupilotmega.xml b/message_definitions/v1.0/ardupilotmega.xml
index c58cc0f627..6501a7d0df 100644
--- a/message_definitions/v1.0/ardupilotmega.xml
+++ b/message_definitions/v1.0/ardupilotmega.xml
@@ -340,6 +340,16 @@
Longitude
Altitude, not used. Should be sent as NaN. May be supported in a future version of this message.
+
+ Provide a value for height above ground level. This can be used for things like fixed wing and VTOL landing.
+ Height above ground level.
+ estimated one standard deviation accuracy of the measurement. Set to NaN if not known.
+ Timeout for this data. The flight controller should only consider this data valid within the timeout window.
+ Empty
+ Empty
+ Empty
+ Empty
+