GR and GPS

[RyanJ]

Hi guys!

 

I came upon an interesting idea, unfortunately I don't know how to calculate it.

 

I was wondering how far out would the GPS satellites be for a car traveling say 100 miles if GR was not factored into their programming? How much out would the distances be?

[insane_alien]

its not just a matter of distance, a object stationary to the surface of the earth without the GR calculations would appear to be moving at a few miles an hour (to the east i think) so the distance its out also depends on the time since the network started.

[swansont]

Hi guys!

 

I came upon an interesting idea, unfortunately I don't know how to calculate it.

 

I was wondering how far out would the GPS satellites be for a car traveling say 100 miles if GR was not factored into their programming? How much out would the distances be?

 

The GR correction is about 45 microseconds a day, which is a 13.5 km error. i.e. about half a km every hour in your positioning. Put another way, a nanosecond for every two seconds elapsed, so the error grows at half a foot per second. Current error is about 30 feet — you double this in just one minute.

 

(the kinematic correction is about 7 microseconds with the opposite sign)

http://en.wikipedia.org/wiki/File:Orbit_times.png

[RyanJ]

That's an impressive margin of error with GR neglected. I didn't think it would be quite that much. Thanks for the information all