[Proj] Why use pj_inv() and pj_fwd() instead of pj_transform() ?

Frank Warmerdam warmerdam at pobox.com
Sat Jun 2 15:39:51 EDT 2007

fabrice martin wrote:
> Hello,
> I'm a recent user of PROJ.4, and I don't exactly understand the
> difference between pj_inv(), pj_fwd() and pj_transform() ? Or said
> differently, why use proj and invproj instead of cs2cs ? I have the
> impression that cs2cs is more powerful than the other programs, since
> it can handle prime meridians (+pm), and also geographic coordinates
> with +longlat .
> Are there special features in pj_inv(), pj_fwd(), or has it been superceded by pj_transform() ?


pj_transform() is a newer function layered on pj_inv() and pj_fwd().  My
intention is that most new applications would use it though there is
some performance overhead to going through it instead of calling the
pj_inv() and pj_fwd() functions directly.

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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