what is the best way to programmatically convert between WKT and Proj4 string?

Question

some shapefiles have a .prj file associated with it. and the .prj file contains the projection info of the shapefile in the format of WKT. Sometimes I need to convert WKT to proj4 string, and sometimes I need to convert it back.

Is there any ready-made library to do this?

Thanks in advance.

Answer 1

I don't know any library, but you can use this site to get the translations: http://spatialreference.org/

EDIT: I found a python script that works with ogr python bindings to do that. Here it is.

Answer 2

The OGR Spatial Reference part of GDAL should do the trick. capooti provided an excellent answer to another question which demonstrates how to peform the translation from a shapefile to WKT. You may also want to check out the class reference. The reverse is simply:

from osgeo import osr

srs = osr.SpatialReference()
wkt_text = 'GEOGCS["GCS_WGS_1984",DATUM["WGS_1984",' \
           'SPHEROID["WGS_1984",6378137,298.257223563]],PRIMEM["Greenwich",0],'\
           'UNIT["Degree",0.017453292519943295]]'

srs.importFromWkt(wkt_text)
srs.morphToESRI() # converts the WKT to an ESRI-compatible format
print "ESRI compatible WKT for use as .prj:" % srs.ExportToWkt()