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<body class='hmmessage'><div dir='ltr'>hi martin and johann<div><br></div><div>thanks for your response.<br><div><br>my apologies for my poor and confusing explanation.</div><div>it might be easier if i use an actual example.</div><div><br></div><div>i have a model in cartesian coordinates like</div><div>x,y,z</div><div>[-0.5, -0.5, -0.5]</div><div>[ -0.5, 0.5 ,-0.5]</div><div> [0.5 ,0.5, -0.5]</div><div>origin [0,0,0]</div><div><br></div><div>i want to place this model onto a globe visualization that requires GEOCENTRIC coordinates.</div><div><br></div><div>the origin of the model in GEOCENTRIC is</div><div><span style="font-size: 12pt;"><br></span></div><div><span style="font-size: 12pt;">[1215019.3092979142, -4736312.191468832, 4081596.540251589]</span></div><div><br></div><div>i now want the model to be relative to the new model origin</div><div><br></div><div><div>x,y,z</div><div>[-0.5 ,-0.5, -0.5]</div><div>[ -0.5 ,0.5, -0.5]</div><div>[ 0.5 ,0.5 ,-0.5]</div></div><div>origin [0,0,0]</div><div><br></div><div><span style="font-size: 12pt;">transforms to</span></div><div><span style="font-size: 12pt;"><br></span></div><div><span style="font-size: 12pt;">x,y,z</span></div><div><div>[?,?,?]</div></div><div>[?,?,?]</div><div>[?,?,?]</div><div>ori<span style="font-size: 12pt;">gin </span><span style="font-size: 12pt;">[1215019.3092979142, -4736312.191468832, 4081596.540251589]</span></div><div><br></div><div><br></div><div>does that make sense?</div><div><br><br>-lucio
<br><br>-----------------------------------
<br><br>lucio_piccoli@hotmail.com<br><br><div><hr id="stopSpelling">To: geotoolkit@lists.osgeo.org<br>From: martin.desruisseaux@geomatys.com<br>Date: Fri, 1 Apr 2016 11:30:04 +0200<br>Subject: Re: [geotk] cartesian to geocentric transform<br><br>
<div class="ecxmoz-cite-prefix">
Hello Lucio<br>
<BR>
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.<br>
<BR>
There is many geocentric CRS, and I'm not sure which one you
are interested in. For example on the following page:<br>
<BR>
<a class="ecxmoz-txt-link-freetext" href="http://epsg-registry.org/" target="_blank">http://epsg-registry.org/</a><br>
<BR>
In the "type" field, select "Coordinate Reference System", then
"Geodetic CRS", then "Geocentric CRS". There is more than 100
entries matching this query.<br>
<BR>
Martin<br>
<BR>
<br>
<BR>
Le 01/04/16 01:57, lucio Piccoli a écrit :<br>
</div>
<blockquote cite="mid:BLU172-W12A248E87221B00B6413AA9F990@phx.gbl">
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<div dir="ltr">hi all
<div><br>
i need some help on converting a mesh model from local origin
cartesian (from a modelling tool) to a geocentric one.</div>
<div><br>
</div>
<div>i found the nice transform from WGS to (ECEF) GEOCENTRIC
which i use to transform the model origin to a geocentric
point.</div>
<div><br>
</div>
<div>
<div> CoordinateReferenceSystem targetCRS =
PredefinedCRS.GEOCENTRIC;</div>
<div> CoordinateReferenceSystem sourceCRS =
PredefinedCRS.WGS84_3D;</div>
<div> MathTransform tr =
CRS.findMathTransform(sourceCRS, targetCRS);</div>
</div>
<div><br>
</div>
<div>i wish to use this point as my local origin for the rest of
the model in geocentric coordinates.<br>
<br>
i do NOT want to transform every point to ECEF (origin earth
centre) , as it will introduce jitter to the visualation.</div>
<div>but rather transform the points to GEOCENTRIC coordinates
*relative* to my own origin.</div>
<div><br>
</div>
<div>does that make any sense?<br>
<br>
-lucio<br>
</div>
</div>
</blockquote>
<br>
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