[geotk] cartesian to geocentric transform

johann sorel johann.sorel at geomatys.com
Fri Apr 1 00:58:25 PDT 2016


Hello,

So if I understand right you just want a translation ?
Take the geocentric point, subtract it with the origin of your model.
Build an affine transform  and set the last column values(translation) 
to the result of the operation above.
That tranform will move your model to the geocentric position.

Still you will have to solve the rotation and scale,
You could solve it using 3 more points which will act as up, right and 
forward vectors.

johann

On 01/04/2016 01:57, lucio Piccoli wrote:
> hi all
>
>
> i need some help on converting a mesh model from local origin 
> cartesian  (from a modelling tool) to a geocentric one.
>
> i found the nice transform from WGS to (ECEF) GEOCENTRIC which i use 
> to transform the model origin to a geocentric point.
>
>         CoordinateReferenceSystem targetCRS = PredefinedCRS.GEOCENTRIC;
>         CoordinateReferenceSystem  sourceCRS = PredefinedCRS.WGS84_3D;
>         MathTransform tr = CRS.findMathTransform(sourceCRS, targetCRS);
>
>
> i wish to use this point as my local origin for the rest of the model 
> in geocentric coordinates.
>
> i do NOT want to transform every point to ECEF (origin earth centre) , 
> as it will introduce jitter to the visualation.
> but rather transform the points to GEOCENTRIC coordinates *relative* 
> to my own origin.
>
> does that make any sense?
>
> -lucio
>
>
>
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