[Proj] ECEF

[Eric Miller]

That isn't quite accurate.  Evenden's libproj4 does not support datums
in any way, but the PROJ.4 from remote sensing has good datum support
with 3- and 7-parameter transformations along with so-called "grid
shift" transformations like NADCON.  Using the command line programs,
one should use "cs2cs" and using the library one should use
"pj_transform()."

It may cause less confusion if Gerald called his reworked and expanded
library "proj5."  Additionally, any coordinate system interface built on
top of Gerald's library that does support datums should probably have a
different name entirely (nothing with "proj" in it).  Just my humble
opinion... 

Eric G. Miller
GIS Analyst
Wildlife and Habitat Data Analysis Branch
Department of Fish and Game

>>> cjmce at lsu.edu 02/26/05 4:07 PM >>>




Noel,

Your conclusion is correct with regard to PROJ4; it does not support
datum
shifts of any kind.  Mr. Evenden is of the same philosophy as John P.
Snyder was in regard to that topic.

Regards,

Cliff

Clifford J. Mugnier
Chief of Geodesy and
Associate Director,
CENTER FOR GEOINFORMATICS
Department of Civil Engineering
CEBA 3223A
LOUISIANA STATE UNIVERSITY
Baton Rouge, LA  70803
Voice and Facsimile:  (225) 578-8536 [Academic]
Voice and Facsimile:  (225) 578-4474 [Research]
======================================================
http://www.asprs.org/resources/GRIDS/ 
http://www.cee.lsu.edu/facultyStaff/mugnier/index.html 
======================================================


Quick first question from a newcomer exploring the  capabilities of
Proj.4
before attempting to compile the code.

I've read the documentation plus recent threads on  this list serve
that
discuss datum shifts (of the 7-parameter variety), which,  apparently,
Proj.4 does not support.  My question is whether  Proj.4 supports
Earth-Centered Earth-Fixed (ECEF) geocentric Cartesian  coordinates or
not
(i.e, lat/lon/hgt => ECEF X/Y/Z).  Seems it would be  simple to build
that
functionality into the Proj.4 code, but I gather that the 
documentation's
references to "cartesian coordinates" means Eastings/Northings  in
projected space, and not ECEF.  Non-support for geocentric datum 
shifting
seems to support this tentative conclusion.  Can someone  confirm for
me?

Thanks, Noel Zinn

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