[geotk] cartesian to geocentric transform

[lucio Piccoli]

hi martin and johann
thanks for your response.

my apologies for my poor and confusing explanation.it might be easier if i use an actual example.
i have a model in cartesian coordinates likex,y,z[-0.5, -0.5, -0.5][ -0.5, 0.5 ,-0.5] [0.5 ,0.5, -0.5]origin [0,0,0]
i want to place this model onto a globe visualization that requires GEOCENTRIC coordinates.
the origin of the model in GEOCENTRIC is
[1215019.3092979142, -4736312.191468832, 4081596.540251589]
i now want the model to be relative to the new model origin
x,y,z[-0.5 ,-0.5, -0.5][ -0.5 ,0.5, -0.5][ 0.5 ,0.5 ,-0.5]origin [0,0,0]
transforms to
x,y,z[?,?,?][?,?,?][?,?,?]origin [1215019.3092979142, -4736312.191468832, 4081596.540251589]

does that make sense?

-lucio


-----------------------------------


lucio_piccoli at hotmail.com

To: geotoolkit at lists.osgeo.org
From: martin.desruisseaux at geomatys.com
Date: Fri, 1 Apr 2016 11:30:04 +0200
Subject: Re: [geotk] cartesian to geocentric transform


  
    
  
  
    
      Hello Lucio

      

      I'm not sure to understand your need. You want to perform a
        transformation between two geocentric coordinate reference
        systems (GeocentricCRS)? If this is the case, then as Johann
        said the transformation can be approximated with a small
        translation, scale and rotation. But the difference is typically
        only a few hundred metres.

      

      There is many geocentric CRS, and I'm not sure which one you
        are interested in. For example on the following page:

      

      http://epsg-registry.org/

      

      In the "type" field, select "Coordinate Reference System", then
        "Geodetic CRS", then "Geocentric CRS". There is more than 100
        entries matching this query.

      

          Martin

      

      

      

      Le 01/04/16 01:57, lucio Piccoli a écrit :

    
    
      
      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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