Thanks for the update. I was operating with old info. At one time, the US military obfuscated GPS data to make it impossible to get position information withing less than 30'. Though I knew they had stopped doing that, I didn't realize GPS had become that accurate. I'd guess there has been some newer technology developed since then as well.GPS is very precise, provided you allow for the differences. Also, with differential GPS, position can be determined within a few centimetres.