[time-nuts] GPS Common View

Bob Camp lists at rtty.us
Thu Jul 8 17:53:42 EDT 2010


Hi

Extracting code phase data from the TBolt may or may not be practical. I'm looking at that as a "future project". 

Right now all I'm really trying to do is see if there is any real interest in an "amateur" common view experiment. With the PICTIC II and a TBolt, you *should* have just about everything you would need to do a comparison between the TBolt's 1 pps and your local standard. Not a lot of cash required since most of us seem to have TBolts already. My *guess* is that a 1 ns resolution counter is probably good enough, so the PICTIC is actually overkill. 

Bob


On Jul 8, 2010, at 9:55 AM, bg at lysator.liu.se wrote:

> Many (most) GPS postprocessing packages can export a timesolution. But it
> is not the usual use of these packages, so it might not be the most
> obvious procedure.
> 
>> From the receiver view, the most common setup for these packages, is
> datasets from a dual frequency receiver, where you want to solve for a
> static solution or maybe a moving receiver (kinematic/ solution).
> 
> Standard measurements are code and phase measurements for L1 and L2, maybe
> also a doppler measurement.
> 
> If I remember the Thunderbolt interface discussions we had correctly there
> is only a code measurement available from the Tbolt.
> 
> At least in the past the online services has been limited to dual
> frequency data and solving for a static position. There was also
> geografical limitations where say a US based service would not process a
> european dataset.
> 
> Still its an interesting project to setup an "amature" Common view process.
> 
> --
> 
>    Björn
> 
>> Hi
>> 
>> From a quick look it's not real clear how you would go about extracting
>> time from the software suite. It's certainly useful for navigation though.
>> 
>> A secondary gotcha is that the TBolt likely has some internal "issues"
>> that distort the data a bit. Running a TBolt on both ends should wash out
>> the ones that are firmware based.
>> 
>> Bob
>> 
>> 
>> On Jul 7, 2010, at 8:54 PM, jimlux wrote:
>> 
>>> Bob Camp wrote:
>>>> Hi
>>>> I just got through poking at a couple of TBolts with Lady Heather. It
>>>> appears that you can indeed get the hardware and software to put the
>>>> TBolt into single satellite mode. That may enable a pretty simple GPS
>>>> common view setup. One way to do it: Somebody picks a set of sats and
>>>> times that make sense. Since the constellation repeats it's going to be
>>>> a fairly simple table of this sat / that time. At those times they run
>>>> their TBolt against something pretty good and log the results
>>>> The logs get put on a site somewhere
>>>> Somebody else wants to do a comparison. They set up to monitor the same
>>>> satellite at the same time. They log the data.
>>>> They download the posted data.
>>>> They run the math on the data, out comes a time comparison between the
>>>> two locations. Should be fairly simple to try out. Anybody with a good
>>>> house standard want to give it a try?
>>> 
>>> Couldn't you run your data against Gipsy/OASIS or similar
>>> http://gipsy.jpl.nasa.gov/orms/index.html
>>> 
>>> 
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>> 
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> 
> 
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