[time-nuts] GPS position averaging

Bob Camp kb8tq at n1k.org
Mon Dec 15 18:46:08 EST 2014


> 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?

I would *guess* that the position reported by the GPS would be the better alternative. The distances (errors) involved are often fairly small. Proving which one is correct may not be easy.  Obviously, the ideal case is the one where there is no error. If the error exists it says that the firmware has some sort of bug. 

Of course *my* code never ever has bugs … :)


> Angus
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