An intriguing story about undersampling

Wow, that's pretty interesting as well.   I'd actually not heard of
this before.

How much difference does accounting for this make in the accuracy of
typical receivers?

On Wed, 08 Jun 2005 15:01:01 +0100, Iwo Mergler
<Iwo.Mergler@soton.sc.philips.com> wrote:

>> So I believe it's speed of light delays that are used, not the Doppler
>> effect.
>
>It's both. Speed of light delays for position, as you described. 
>The Doppler shift is used for velocity calculation.
>
>The (general) relativistic effect is an increase in frequency, 
>equivalent to all satellites drifting slowly towards you.
>
>It's due to the fact that time passes slower inside the gravity well.
> 
>> My guess is that relativistic corrections are needed to keep the atomic
>> clocks in sync due to time dilation caused by the orbital velocity.
>> After all, relativistic time dilation was verified in experiments with
>> atomic clocks aboard aircraft, and the satellites are a lot faster.
>> 
>> Scott
>
>I'm not sure if special relativity applies in this case. The result is
>the opposite, the clocks on the SVs seem to go faster, not slower.
>
>Kind regards,
>
>Iwo

Eric Jacobsen
Minister of Algorithms, Intel Corp.
My opinions may not be Intel's opinions.
http://www.ericjacobsen.org

Eric Jacobsen wrote:
> Wow, that's pretty interesting as well.   I'd actually not heard of
> this before.

> How much difference does accounting for this make in the accuracy of
> typical receivers?

(snip regarding special and general relativity and then GPS system.)

The first google hit,

http://www.phys.lsu.edu/mog/mog9/node9.html

seems to have a pretty good explanation.

-- glen

On Wed, 08 Jun 2005 15:13:05 -0700, glen herrmannsfeldt
<gah@ugcs.caltech.edu> wrote:

>Eric Jacobsen wrote:
>> Wow, that's pretty interesting as well.   I'd actually not heard of
>> this before.
>
>> How much difference does accounting for this make in the accuracy of
>> typical receivers?
>
>(snip regarding special and general relativity and then GPS system.)
>
>The first google hit,
>
>http://www.phys.lsu.edu/mog/mog9/node9.html
>
>seems to have a pretty good explanation.
>
>-- glen

There are some details where they lost me, but generally very
informative!


Eric Jacobsen
Minister of Algorithms, Intel Corp.
My opinions may not be Intel's opinions.
http://www.ericjacobsen.org

Eric Jacobsen wrote:

> Wow, that's pretty interesting as well.   I'd actually not heard of
> this before.
> 
> How much difference does accounting for this make in the accuracy of
> typical receivers?
> 

Less than 40us per day. Not a huge problem.

Regards,

Iwo