[time-nuts] question about Thunderbolt geo acuracy

Magnus Danielson magnus at rubidium.dyndns.org
Thu May 10 13:08:37 UTC 2012


On 05/10/2012 02:50 PM, swingbyte wrote:
> Hi all,
> 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.

There are many sides to this issue. You will most definitely be best 
served by a choke-ring or similar antenna that suppresses multi-path 
reflections. In addition to that, you would want Lady Heather to do a 24 
hour position averaging. This should give you an OK solution, but really 
not the best achievable.

Accurate height data is complex, since besides the receiver and antenna 
issues, height data has more uncertainty than longitude and latitude 
measures, and also since even if precise WGS84 height is achieved, you 
would need to correct it to your datum, your sea-level etc.

You would also like to have better ionspheric correction than a plain 
GPS solution gives you, but the Thunderbolt does not give you direct 
support for such corrections.

Exactly how much effort you need to do depends on how accurate you need 
it, +/- 10 m, 1 m, 1 dm, 1 cm or 1 mm.

Cheers,
Magnus



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