The biggest thing around is the ground.... remember 3 feet above the ground or pavement surface fairly well gets you out of most ground effect. Doing range checks with the aircraft on the surface / ground for the most part is a waste of time. The effects of being close to the ground can sometimes increase or decrease the measured distances a surprising amount. Approx 3 feet above the ground neutralizes most ground effect but at the same time doesn't increase the range like 10 or 15 feet above the ground would.
Lee H. DeMary
AMA 36099