There are two NDB’ s, one 20 NM inland, and the other 50 NM inland from the coast. Assuming that the error caused by coastal refraction is the same for both propagations, the extent of the error in a position line plotted by an aircraft that is over water will be:
the same from both beacons when the aircraft is on a relative bearing of 180° and 360° .
greater from the beacon that is 20 NM inland.
the same from both beacons when the aircraft is on a relative bearing of 090° and 270° .
greater from the beacon that is. 50 NM inland.