[time-nuts] Strange GPS behaviour

Bob Camp lists at rtty.us
Sun Dec 30 02:56:46 UTC 2012


Hi

The interesting thing is that you sometimes can get a position hold receiver to report it's estimated location…. Not so much on current product, but on some of the old stuff.

Bob

On Dec 29, 2012, at 9:51 PM, Jim Lux <jimlux at earthlink.net> wrote:

> On 12/29/12 6:34 PM, Bob Camp wrote:
>> Hi
>> 
>> The gotcha is that often the "navigation" and "timing" receivers are identical in terms of hardware. There is no upgraded hardware in the timing device.
>> 
>> When you put a receiver into position hold, you are telling it "I don't care about the location solution". It reduces the weight of that part of the filter. Yes, that's only one way to look at it and there are other ways to look at it.
> 
> 
> or, another conceptual model is: I'm fixed, I know where the transmitting satellite is, and can calculate range and doppler a priori, so anything else must be local clock variation and propagation.  And you can average out the propagation among multiple satellites (or use one satellite as your timing reference)..
> 
> Particularly if you are post processing and have precise ephemeris data for the satellites....
> 
> 
> 
> 
> 
> 
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