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[aprssig] differential corrections available to public(insome places)

Gerry Creager N5JXS gerry.creager at tamu.edu
Tue Mar 15 04:23:29 UTC 2005


Rich Garcia wrote:
> Initially that is what was tested and as Gerry stated back then we needed
> DGPS stations at 60 or so mile intervals
> for optimum coverage and accuracy. The other issue was 15 or so second
> updates were necessary and here for the 60
> mile range that would mean 3 or so hops that a) Adds time delays and b)
> saturates the channel (maybe not fully) but
> quite a bit when you think of one packet generating 2 others every 15
> seconds plus the traffic. Gerry...what would
> it be like now, how far would the correction be valid for ?

The multiple hops don't tend to screw up the corrections accuracy.  If 
the correction arrives late, it's ignored.  Channel saturation is a 
bigger feature.  That said, if it can't be sent with a max of 2 hops, 
it's probably out of date when received.  Big tower, no digi's lots o' 
power.  You know... what we tell folks not to do.

Current algorithms should allow a more dispersed network.  I'm not 
comfortable generalizing beyond that:  Too many different GPS systems of 
varying ages, software/firmware releases, and manufacturers.

... deletia follows...

-- 
Gerry Creager -- gerry.creager at tamu.edu
Texas Mesonet -- AATLT, Texas A&M University	
Cell: 979.229.5301 Office: 979.458.4020 FAX: 979.847.8578
Page: 979.228.0173
Office: 903A Eller Bldg, TAMU, College Station, TX 77843




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