Interesting. Predictable error. Some gps units will average over multiple measurements but it takes time. Time means vulnerability if a weapon system.
As I said, each time I set a flag, I put the GPS down there to read and average at lest 1,000 points. Even so, I wound up with an approximately 50 ft radius circle.
The landowner for whom I'm doing an archaeological survey just retired from the Army. He said their field units (with algorithms to subtract out the encoded jitter) were good to <1 meter CEP...