Failsafe BUG: Terrain Data Missing - Even when using rangefinder in Copter 4.3


Arducopter 4.3.X does not arm due a “Terrain Data Missing” error caused by a bug not present until 4.2.X. We use this function for over 3 years with no problems. Switching back to V4.2.X all works fine. All our missions use waypoints with “Terrrain” altitude type.

This error is happening with working rangefinder (radar) and TERRAIN_ENABLE,0. The Rangefinder has a working height of 20m, so “Data Missing” should happen only after I pass 20m. Please correct the code. We do not load terrain data since we fly very low (crop sprayers) and we need radar information to follow terrain.

Thank you

The error message only appears after sending a mission using terrain as the frame of reference. We keep getting: “PreArm: Terrain Disabled”. We are not using the terrain database, but a rangefinder to follow the terrain. WPNAV_RFND_USE is set to 1.

The rangefinder behavior is very strange as well. It spikes 100 m and then it appears to work well. But the prearm message doesn’t go away.

We are still able to fly in loiter mode, and send missions using the relative frame of reference. The same radar and the same driver works great in V4.2.3.

Link to log: