[time-nuts] GPS position averaging

Bob Camp kb8tq at n1k.org
Mon Dec 15 19:51:54 EST 2014


Hi

Actually there may be a Time Nuts relevant reason for wanting to know the true / correct / survey location. 

If your desire is to know UTC to ns or something like that, an indicated position error *probably* relates directly to a time error. Being able to correct the position error may allow you to better estimate the UTC time error. 

Bob

> On Dec 15, 2014, at 6:39 PM, Angus <not.again at btinternet.com> wrote:
> 
> On Mon, 15 Dec 2014 17:55:20 -0500, you wrote:
> 
>> Hi
>> 
>> Simple answer - there is no simple answer.
>> 
>> You will get significantly better results by intelligently processing the data than by a giant “average everything in sight” approach. 
>> 
>> Also consider that various GPS modules seem to have offsets in their nav solution. The NIST papers on various GPSDO’s show this pretty clearly. Simply having a “correct” solution may not help as much as you might think.
>> 
>> Of course if you want a truly correct solution, your local surveyor is indeed your best friend. He probably has a GPS gizmo that with about a half hour or sitting there, tell you where you are to under an inch. Who knows how much that will cost. It probably depends on how interested you can get him in coming over and looking at your toys. 
> 
> But is it the closest to the 'true' position that you really want, or
> the best estimate of where the particular GPS you are testing thinks
> it is?
> 
> Angus
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