A navigation target could not be used (ERR NAVIGATION)

What ArduPilot says:

• ERR NAVIGATION (Subsys 22)

Code 2: a destination could not be set because the ground height it needs was missing (a Guided target or RTL's first leg, with heights above terrain); in RTL the copter then lands. Code 4: Circle was given a centre with a height above terrain and has no terrain data, so it circles around where it is. Code 5: a Guided target, a “fly to here” from the ground station or a companion computer, lies outside the fence and was refused; the aircraft carries on with what it was doing. Codes 3 and 6 belong to RTL and are explained with its messages.

What to do, most likely first

1. Code 5: the point chosen on the map is beyond the fence, or above its ceiling.

   CheckCompare the target's distance from home and its height with FENCE_RADIUS and FENCE_ALT_MAX.

   FixChoose a target inside the fence, or set the fence before the flight to the area you mean to use.

2. Codes 2 and 4: the command uses a height above terrain and there is no terrain data or rangefinder reading for it.

   CheckA terrain message or “ERR TERRAIN-2” is in the log near it.

   FixSend targets with heights relative to home, or make the terrain source dependable: see “Failsafe: Terrain data missing”.

Parameters to look at

Where to do it:Failsafe ExplainerFailsafe Explainer