----- Original Message -----
From: "Brian Kraut" <engalt@EARTHLINK.NET>


> You can buy a copy of the standard for $80.00 at rtcm.org.  My company is
an RTCM member, but we don't have a copy.

Thanks, but do you know of anywhere I can get it for free? This would work
as a last resort, but the GPS I'm planning to buy only costs $100ish!

> What you are planning is pretty much the same thing any differential
station does so there is no problem with your theory.  The only problem I
see is that the Etrex won't take RTCM-SC104 differential corrections as far
as I know.

Actually, it does. It'll take both RTCM and NMEA input and can output NMEA,
text, or Garmin proprietary.
BTW, I'm not planning to feed the RTCM into the Etrex, but rather into an
OEM GPS. I'd like to use the Trimble LassenSQ module, but I'm not sure that
it supports DGPS corrections in any format.
I could always, as you say, just do the processing offboard the GPS, in a
microcontroller. That way I wouldn't even have to bother with RTCM or any
other strange formatting. I can just make up my own arbitrary format to suit
my needs.
Do you know of a good DGPS tutorial or reference where I can find more
information on calculating and using DOP and position error data, as well as
implementing DGPS corrections offboard the GPS unit? Thanks!

- Robert

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