[aprssig] TAPR Differential GPS Reference Station

Robert Bruninga bruninga at usna.edu
Wed Apr 22 08:39:47 EDT 2009

> It would be appreciated if anyone else knows 
> how any of the client applications massaged 
> or used any of this data, they could 
> chime in here.

The client really doesn't have to do anything with it except
strip off the packet header and pass the DGPS data as is out the
NEMA serial port to the GPS.  The GPS the corrected its position
to the accuracy of the DGPS and reported same back via the NMEA
serial port to the APRS application.

But again, as noted, Tom Clark W3IO, first borrowed a $50,000
DGPS receiver and put it on the air in the Maryland area and we
experimented with it.  APRSdos and Kenwood would pass this to
attached GPS's for the better positioning.  But again, the DGPS
had to be transmitting so often (15 seconds) to have any real
value, that the cost to the channel loading was just too high.
Besides, then the USA turned off selective availablity and it
was not needed.  Now you can buy your own DGPS or WAAS
augmentation receiver for a few hundred bucks and add it to your
own system without having to send it over the APRS channel.

Bob, Wb4APR

> Steve Dimse wrote:
> >
> > On Apr 21, 2009, at 2:16 PM, Boyd Prestwood K5YKG wrote:
> >
> >> However it was my understanding that the site from which
the Ref 
> >> Station transmitted had to be surveyed for "exact"
> >
> > The TAC-2 software performed a 24 hour integration of 
> position, this 
> > was found to produce a very accurate position. Surveys were
> > necessary. Otherwise, my recollections match with yours.
> >
> > Steve K4HG
> >
> >
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