My experience with pre waas gps was an accuracy of about 100' radius of error, or about 30m. With waas, that went down by a factor of about 10. This was with a 12 channel receiver, so you could get a lot of satellites, but non waas is not all that bad. I was able to find Ellicot's Rock with an old Magellan pre waas before Clinton turned SA off, and that's a 12" diameter rock on the vertical bank of the West Fork of the Chatooga river on the NC/GA state line, set there by a surveyor in the late 1700's/early 1800's.

Not responsible for advice not taken...