Adam said:

>Better resolution would be nice for other uses, but not necesary.  So I'm
>planning on having one sit at my car (fixed location) with a data logger, and
>another on my bike.  I'll run the two sets of data through the computer later
>and normalize the bike data according to the car data.  That should eliminate
>most of the problem with SA.  Relative mapping is all that's necessary, I don't
>need to know the absolute locations of the trails.
>
>I live in the great lakes region, so I could use the dgps signals sent around
>300kHz, but the receivers (both do it yourself and ready made) are more
>expensive than the surplus gps receivers, and only gives about 5M resolution.
>


  Adam:

  Be aware that this system only works well when both receivers have
  acquired the same set of satellites. Even if they are right next to
  each other this is not guaranteed.

  Reg Neale