The fence margin or a circle's radius is wrong

What ArduPilot says:

• Invalid FENCE_MARGIN value
• Circle FENCE_MARGIN is less than FENCE_RADIUS
• Invalid FENCE_MARGIN_XY value
• Invalid Circle FENCE_RADIUS value
• Circle FENCE_MARGIN is greater than FENCE_RADIUS
• Polygon fence margin is less than inclusion circle radius

FENCE_MARGIN (2 m by default) is how far inside the fence ArduPilot tries to stay. It must not be negative, and no circle may be smaller than it: neither FENCE_RADIUS (the circle around home, 300 m by default) nor an inclusion circle drawn in the ground station. FENCE_RADIUS is checked even when the circle is not selected in FENCE_TYPE. In this version the two “… is less than …” messages are worded backwards: they appear when the radius is smaller than the margin.

What to do, most likely first

1. FENCE_RADIUS is smaller than the margin, often 0 because the circle is not used.

   CheckCompare FENCE_RADIUS with FENCE_MARGIN.

   FixGive FENCE_RADIUS a real value (the documented range is 30 to 10000 m), even if the circle is not selected in FENCE_TYPE: the check runs regardless.

2. An inclusion circle drawn in the ground station has a radius smaller than the margin.

   CheckRead the fence back in the Plan screen and look at the radius of each circle.

   FixDraw the circle larger, or delete it, and write the fence to the aircraft again.

3. The margin was typed as a negative number.

   FixSet FENCE_MARGIN to a positive distance in metres; 2 is the default.

Parameters to look at

Where to do it:Failsafe Explainer