Originally Posted by
peter9477 How much does it have you "moving around", and where are you (e.g. near buildings?) when you're doing this.
It's the nature of GPS that it doesn't return exactly the same reading every time, and the location calculation has you "move around" a fair bit. Under the right conditions, on average, it will be fairly close (within a 10 meters or better), but any individual reading can be much farther off than that, especially under poor conditions.
I don't know whether Magellan does good averaging or not. If it does not currently, it's something that could be improved with software. Otherwise you're just looking at the nature of GPS in its current form.