What I love about this forum is that, apart from the occasional verbal sparring match that doesn't seem to go anywhere, is that I learn a lot from it. It is very good to learn how there are DGPS systems that could do this.
My only question though is why do you have such fine tolerances mickjobill? as it seems to me to be some techie saying I want this exact thing when a bit of latitude would not change the angles very much and give pretty much the same picture.