[OSRS-PROJ] Re: make geocentric XYZ one of proj's output choices

[Clifford J Mugnier]

Frank,

Now if you use a 3x3 orthogonal rotation to a tanget or secant plane to the
ellipsoid and drop the third component, Z; you will have the ellipsoidal
implementation of the Polyhedric or Polyeder.  There are topo sheets still
published on this ancient projection.  (Sometimes called the Muffling).

Cliff Mugnier
LOUISIANA STATE UNIVERSITY
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Dan Jacobson wrote:
> Can somebody enhance proj to make geocentric XYZ one of the output
> choices.  It is used internally but it is a shame that one can't chose
> to output it.

Dan,

Because your wish is my command, I have incorporated geocentric coordinate
support in a form accessable to the end user.  The fake projection
"geocent" may now be used with the pj_transform() function and the cs2cs
user program to define a coordinate system in geocentric coordinates.
The linear units are also applied to this geocentric coordinate system, but
prime meridians, x_0, y_0 and other non-ellipsoid parameters are ignored.

eg.

% ./cs2cs +proj=latlong +ellps=WGS84 +to +proj=geocent +ellps=WGS84
0 0
6378137.00      0.00 0.000
0 90
0.00    0.00 6356752.314
0 90 1000
0.00    0.00 6357752.314

Geocentric coordinates should not be used with the proj program as it
only operates in 2D.  It is only for "real" projections.

I would encourage you to check out the latest PROJ.4 CVS source and test
the new facility as a "punishment" for requesting the feature.

PS. I will release a new version of PROJ.4 as soon as I am happy with my
updated translation of the EPSG 6.2.2 database to a PROJ.4 initialization
file.

Best regards,

--
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam,
warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent


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