[osg-users] Site localization equations for RTK GPS

J.P. Delport jpdelport at csir.co.za
Mon Apr 4 02:54:30 PDT 2011


Hi,

On 02/04/11 19:09, Brett wrote:
> Hi,
>
> I was wondering if any of the equations or libraries used with osg or
> vpb allow the user to perform site calibration / localization for RTK
> GPS. ie. I am trying to create a transform to convert WGS84 coordinates
> into a local Cartesian coordinate system based on matching 3 or more GPS
> survey points with locally defined / measured points. The local points
> are in a localized 'flat' coordinate system. This may require
> calculating a local 'datum' using something like a Molodensky or
> Bursa-Wolf transform. I am looking for information to develop these
> equations or some open-source software to perform this calculation. Any
> help or advice is greatly appreciated. Thanks in advance.

OSG's EllipsoidModel can do some of this for you. See:

computeLocalToWorldTransformFromLatLongHeight

Basically you create a transform like this for a reference lat/long/alt 
point. This transform puts LLA points into a coordinate system on a 
"local tangent plane" (google this) at the reference point. In the local 
system you can then align your device axes/coordinate system to the 
reference axes/coordinate system by using multiple points and some 
optimisation algorithm.

So, in one direction you go from LLA -> ECEF -> local coords -> device 
coords.

cheers
jp

>
> Brett
> _______________________________________________
> osg-users mailing list
> osg-users at lists.openscenegraph.org
> http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
>

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