[time-nuts] Computing GPS Distance Error in Time

[Chris Albertson]

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