[time-nuts] question about Thunderbolt geo acuracy

[Jim Lux]

On 5/10/12 9:33 AM, Attila Kinali wrote:
> On Thu, 10 May 2012 17:01:48 +0200
> bg at lysator.liu.se wrote:
>
>>> On Thu, 10 May 2012 22:50:15 +1000
>>> swingbyte<swingbyte at exemail.com.au>  wrote:
>>>
>>>> Hope this isn't too chat roomy, however, I have need of a survey precise
>>>> geolocation type gps.  I was wondering if the precise timing abilities
>>>> extend to its precision in position output?  I have a thunderbolt and
>>>> one of those conical white aerials from china and would like to know if
>>>> this combination will give me accurate height data.
>>>
>>> How fast do you need it?
>>>
>>> One project i'm involved with uses a LEA6-T with its phase data output
>>> and averaging over several hours to get x/y resolutions in the 2-4mm
>>> range.
>>> I'm quite sure you can do something similar with altitude as well.
>>
>> That is relative positions over a baseline of ca 100m. Not absolute
>> positions.
>
> The "Baseline" is definitly larger than just 100m. the current testing
> field is spread over the side of a mountain... I haven't looked at the
> scale of the map, but i'd say it was somewhere in the range of 2-5km.
>
> I do not know whether they use fixed reference stations. I am not aware
> of any.
>


There are "virtual" reference stations available in a lot of places, 
where they use data from carefully surveyed geodetic quality receivers 
to create a synthetic reference.  A common acronym is HARN (High 
Accuracy Reference Network).  Some are free, others have a user fee of 
some sort(depends on where they are, and who set it up.)

And, of course, if you can post process, then things like GIPSY can 
help.  I believe the GIPSY folks ingest data from all over the world.