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[aprssig] Position Ambituity in APRS!

Scott Miller scott at opentrac.org
Tue Jan 8 17:21:24 UTC 2008


For what it's worth, OpenTRAC has a positional ambiguity represented as 
a 16-bit integer in meters - enough for a radius of up to 65 km.  Though 
in looking at the spec, I think it needs to be more clearly defined what 
the 'estimated error radius' is.

One of these days I'll have time to work on it some more.  I'm getting 
there - as of yesterday, I'm no longer officially employed full time for 
the first time since... well, since I got my first full-time job.  Not 
that it affects the number of hours I work each week, but now I get to 
spend a few more of those hours on APRS and radio stuff!

Scott
N1VG

Steve Dimse wrote:
> 
> On Jan 8, 2008, at 6:55 AM, Steve Dimse wrote:
> 
>>  For ambiguities that do not cross the poles or equator (the only case 
>> allowed by the protocol), the border away from the equator is shorter 
>> than border towards the equator, making it a trapezoid.
> 
> To be correct, this statement should be
> 
> For ambiguities that do not reach or cross the poles or cross the 
> equator, the border away from the equator is shorter than border towards 
> the equator, making it a trapezoid.
> 
> Minor difference, but I think the protocol does allow ambiguity to reach 
> (but not cross) the poles, and the linear projection of this would be a 
> triangle.
> 
> Steve K4HG
> 
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