PostGIS

NOTE - You must edit the PostGIS Makefile and make sure that USE_GEOS=1 is set. Also adjust GEOS_DIR to point to your GEOS installation directory.

1. Download PostGIS source from http://postgis.refractions.net

2. Untar PostGIS into the contrib subdirectory of the postgresql build directory. The contrib subdirectory is located in the directory created in step 3 of the PostgreSQL installation process.
3. Change to the postgis subdirectory
4. Edit the Makefile to enable GEOS support (see the note above)
5. PostGIS provides a manual in the doc/html subdirectory that explains the build process (see the Installation section)
6. The quick and dirty steps to install PostGIS are:

      cd contrib
      gunzip postgis-0.8.0.tar.gz 
      tar xvf postgis-0.8.0.tar 
      cd postgis-0.8.0 
      make 
      make install 
      createlang plpgsql yourtestdatabase 
      psql -d yourtestdatabase -f postgis.sql 
      psql -d yourtestdatabase -f spatial_ref_sys.sql
   

The better way to install PostGIS is to carefully follow the instructions in the PostGIS manual in the doc/html subdirectory or the online manual at http://postgis.refractions.net/docs