[Proj] Two questions about Proj

Eric Miller EMiller at dfg.ca.gov
Fri Jan 20 12:49:09 EST 2006

It shouldn't take you long to find examples of using the PROJ4 library from other programs.  A couple of emails today have examples.

Generally the easiest is to use the pj_transform function for the conversions.  You just have to make sure your from/to coordinate systems are defined correctly.  The library supports NADCON datum transformation for NAD27, which is nice.  

All of the State Plane coordinate systems have definitions in the proj/nad/stateXX files.  However, be careful about the multiple versions of State Plane Coordinate Systems.  What are the units? meters? us-ft? ft?  Not everyone has been very good about using the correct units even though NAD27 is supposed to be in "us-ft" (different from "ft") and NAD83 is supposed to be in meters (though some folks have used "us-ft" or even "ft").

>>> andy.canfield at gmail.com 1/20/2006 8:17 AM >>>
Actually I was meaning something different in my questions because I
didn't realize most folks use Proj4 from the command line. What I was
really meaning was how do I find an example of using it from C or C++
as a dynamic library or compiled source into my project? I need to
translate coordinates from Lat Lon NAD 83 to State Plan and Vice Versa
and I would rather not have to write it if Proj4 already supports
doing it.

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