[Mapserver-users] ESRI .prj and PROJ epsg

[Frank Warmerdam]

Kieran J. Ames wrote:
> Is anyone aware of a means to translate ESRI's .prj files and find the
> equivalent PROJ epsg entry?
> 
> eg:
> GEOGCS["GCS_North_American_1983",
> DATUM["D_North_American_1983",
> SPHEROID["GRS_1980",6378137,298.257222101]],
> PRIMEM["Greenwich",0],
> UNIT["Degree",0.0174532925199433]]
> 
> How do I know what to assign to variables like
> +proj=
> +lat_1=
> +lat_2=
> +lat_0=
> +lon_0=
> +x_0=
> +y_0=
> +lonc=
> +alpha=
> +k=
> +ellps=
> +datum=
> +units=
> +no_defs
> no_defs

Kieran,

The OGRSpatialReference class includes methods for transforming between OGC WKT,
ESRI WKT and PROJ.4 coordinate system formats.  However, it doesn't normally
figure out what EPSG entry would go with a given coordinate system description
as this is somewhat hard.

These services are available in various forms - C++, Python and commandline
programs.  Some information is available at the following url, or contact me
for a script tailed to do the translation.

   http://gdal.velocet.ca/projects/opengis/ogrhtml/osr_tutorial.html

However, in a case like the GEOGCS you list agove, it is often sufficient
to use:

  +proj=latlong
  +a=6378137
  +rf=298.257222101

Best regards,
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