[aprssig] Differential GPS?

Robert Bruninga bruninga at usna.edu
Mon Apr 20 20:08:35 EDT 2009

Does anyone do differential GPS in APRS?

There is a provision in APRS that will allows someone to connect
a TNC to a GPS differrential receiver and then transmit those
corrections to a mobile on the APRS channel.  We experimented
with it in the early days, but I just don't see that it is
something we need to continue to support.

Reason being that we found  you needed frequent DGPS
transmissions to have any value, and the APRS channel could not
handle a DGPS transmission every 15 seconds just for one or two
people to use it.  Yet, if you reduced the DGPS rate to say once
a minute, then the DGPS data was so stagnant, that there was
little value added.

Of course it was a benefit back when selective availablility was
on, but now that the US government leaves it off, we don't need
DGPS (integrated into APRS).  Also, back then the DGPS receier
cost maybe $50,000.  Now, I think anyone can buy one at the boat
store?  And if he needs it, he feeds it directly into his own

Can we remove the DGPS-on-APRS-channel function it to save code?


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