1st case: Spawn a MQ4A Greyhawk and make it take off. Go to UAV Terminal and command it to loiter over a montaineous/hilly terrain (I very often use 2000m altitude and 1500m loiter radius), be on gunner seat and try to aim to a specific position when it is flying over the mountains.
2nd case: Spawn an AR-2 darter and make it take off. Go to UAV Terminal and command it to go somewhere and specify the altitude (I very often use 500m altitude). The more irregular the terrain between the UAV and the destination, the more evident will be how it loses time "correcting", and even getting stuck.