[time-nuts] Computing GPS Distance Error in Time

Bill Dailey docdailey at gmail.com
Mon Nov 4 12:30:49 EST 2013


The pps on that unit is good.  Compares favorably to the ublox6T. I can't say how favorably.  

I am working on quantifying its pps as compared to my 2 fury units and the ublox 6T.  

Awaiting a 8 antenna splitter, and dso.  

Have another trick up my sleeve but need a Linux kernel hacker.  I don't want to go down another rabbit hole if I can avoid it.

Bill

Sent from mobile

> On Nov 4, 2013, at 11:07 AM, Chris Albertson <albertson.chris at gmail.com> wrote:
> 
>> On Mon, Nov 4, 2013 at 3:51 AM, Bob Camp <lists at rtty.us> wrote:
>> 
>> ..... I can guess it's a vector difference between each two successive
>> points converted to ns,
> 
> 
> That vector difference has to include altitude.   Then as you say, convert
> distance to time via the speed of light.  But I think this is only the
> upper bound of the error, it could be much less because there are multiple
> satellites in view.   That 3 ns per meter rule of thumb is very
> conservative.
> 
> But on the other hand,...   On your specific make and model of GPS they
> could have simply dropped precision on the time, thinking that "0.01
> second is good enough" and allowed some approximations.   You can't assume
> the calculation is perfect.  You'd have to measure.  Is there a spec for
> timing error?
> -- 
> 
> Chris Albertson
> Redondo Beach, California
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