Michael Rigby-Jones wrote :

> >
> >Aren't most sold GPS devices today actualy D-GPS devices ?
> >
> >Jan-Erik.
> 
> 
> I thought that differential GPS required two GPS receivers, 
> one fixed at a known location and the other mobile receiver.
> 
> Regards
> 
> Mike

Yes, but you don't have to own both yourself.

In Sweden that state runs "fixed" GPS'es that resends
the diff-info and many/some GPS receivers sold in Sweden
has an built in recevier for this correction info, so they
are true DGPS devices. There are also option receivers
for this correction signal that can be attached to a
non-DGPS receiver, if I'm not wrong.

The correction signal is also sent over the RDS (Radio
Data System) on the FM band all over Sweden.

Anyway, I've also read that DGPS isn't realy needed
anymore since the "error" in the GPS signal has been
removed.

Jan-Erik.



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