[Proj] (no subject)

Frank Warmerdam warmerdam at pobox.com
Wed Jul 30 01:36:51 EDT 2008

usha regadi wrote:
> hello
>       give me procedure to perform inv projection operation to convert 
> the coordinates from x,y to  (lambda, phi)
> regards
> usha


I think you need to give more context to get a good answer.  Do you want
to do it with commandline utilities?  C API?  Do you just want the math?

What projected coordinate system are you interested in?  I'll assume
you mean projected easting,northing by x,y and longitude,latitude by
lambda,phi.  If that is so, perhaps a commandline example for a particular
projection would be helpful.

proj -I +proj=utm +zone=11 +ellpse=WGS84 < in.dat > out.dat

in.dat might contain a value like:

400000 3730000

and then out.dat will be written as:

118d4'44.85"W   33d42'18.962"N

In the above command, the -I means inverse (ie. projected to geographic rather
than geographic to projected), and +proj=utm +zone=11 +ellps=WGS84 defines the
coordinate system.

Keep in mind, the quality of the answer you get does bear some relation to
the quality of the question.

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    | President OSGeo, http://osgeo.org

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