[aprssig] RE: GBAS

Gerry Creager gerry.creager at tamu.edu
Sun Feb 10 18:48:48 CST 2008

I remember those days.  For awhile I sent it out here in College 
Station, TX, too.  Few folks took advantage of it, though.

And if you go back in history, when I used APRS for a cow-tracking 
research program, I sent differential corrections to the cows, and to 
several fixed sites around the pasture, allowing me to correct the cows' 
positions to sub-bovine accuracy.  Check the archives for Cows In Space...


Robert Kirk wrote:
> At 05:20 AM 2/10/2008, you wrote:
>> What would be cool is if APRS supported an error correction uplink 
>> capability
>> You would need a DGPS capable input GPS
> Tom Clark W3IWI did just that 10 or more years ago in the Washington DC 
> area, long before WAAS & GBAS, and while selective availability was 
> still in effect.
> He had access to precision GPS corrections (from his job at NASA)  and 
> broadcast a  one line dgps message about once a minute over the regular 
> APRS frequency. The message would go thru your TNC into your GPS and 
> correct your position to WAAS class accuracy.  It worked like a charm, 
> well before the Coast Guard's ill-fated DGPS program. I could pilot my 
> boat with impunity.
> It was experimental and didn't last long for a number of reasons (One 
> 19th century curmudgeon, WB..something or other, for instance, didn't 
> like the once a minute transmissions clobbering his bandwidth :-), but 
> it was a real trailblazer.
> Bob Kirk
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Gerry Creager -- gerry.creager at tamu.edu
Texas Mesonet -- AATLT, Texas A&M University	
Cell: 979.229.5301 Office: 979.458.4020 FAX: 979.862.3983
Office: 1700 Research Parkway Ste 160, TAMU, College Station, TX 77843

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