[gdal-dev] GDAL and PROJ.4

[Frank Warmerdam]

Ben Discoe wrote:
> So, i went and looked at the PROJ.4 page, http://www.remotesensing.org/proj/
> and found a binary for Linux, but not Win32. Downloaded the latest source
> and built it, copied "proj.dll" to the GDAL bin directory, and finally it
> works. (Could we add a binary release for Win32 to the PROJ.4 site, like
> there is for Linux?)

Ben,

It is my intention to prepare a proper PROJ.4 binary distribution for Windows
at some point. 

> However, the results i'm getting from
> OGRCreateCoordinateTransformation::Transform are definitely wrong. Perhaps
> there is some trickiness.
> 
> From: "+proj=longlat +ellps=WGS84 +datum=WGS84 "
> To: "+proj=utm +zone=10 +ellps=clrk66 +datum=NAD27 +units=m "

To successfully do the datum shift, PROJ.4 needs to be able to find the
datum shift files. On windows this process is a bit more challenging than
with a default unix install. You should be able to define the PROJ_LIB
environment variable, and point it to the PROJ\NAD directory. 

Also, ensure that you have "preprocessed" the datum shift files. With the
latest PROJ.4 from CVS you should be able to "nmake /f makefile.vc nadshift"
in the PROJ\SRC directory to process the datum shift files in PROJ\NAD. 

In the longer term I hope this process will be smoother, especially the
mechanisms for finding the datum shift files. 

Best regards,

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