Convert SRText To PROJ4TEXT

Question

I'd like to convert the following for updating my spatial_ref_sys table.

PROJCS["USA_Contiguous_Albers_Equal_Area_Conic_USGS_version",GEOGCS["GCS_North_American_1983",DATUM["D_North_American_1983",SPHEROID["GRS_1980",6378137.0,298.257222101]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Albers"],PARAMETER["False_Easting",0.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",-96.0],PARAMETER["Standard_Parallel_1",29.5],PARAMETER["Standard_Parallel_2",45.5],PARAMETER["Latitude_Of_Origin",23.0],UNIT["Meter",1.0]]

The matching spatialreference.org/ref/sr-org/6703 link for this item seems to come up blank. Also, tried gdalsrsinfo but it errored with ERROR 6: No translation for Albers to PROJ.4 format is known.

How do I translate the above for that field? Any other tools to get a full, proper INSERT statement for inserting the proper data into spatial_ref_sys?

UPDATE: The above data comes from the 2 PRJ files found in http://www.america2050.org/maps/, third link to the ZIP files. I would like to import these maps into my database to run queries against some data.

Answer 1

When I open those files in QGis the srs is epsg:5070 - and the boundaries seem to be in the right place (when compared to a known good 4326 states file).

Answer 2

The projection is officially known as EPSG:5070 and included in the EPSG registry and the latest GDAL builds since version 1.9. It is not included in spatialreference.org, because that site has been lacking care for some time.

SR-ORG:6703 is not an official code that GDAL or PROJ.4 will know.

You can run gdalsrsinfo epsg:5070 and it returns:

PROJ.4 : '+proj=aea +lat_1=29.5 +lat_2=45.5 +lat_0=23 +lon_0=-96 +x_0=0 +y_0=0 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs '

OGC WKT :
PROJCS["NAD83 / Conus Albers",
    GEOGCS["NAD83",
        DATUM["North_American_Datum_1983",
            SPHEROID["GRS 1980",6378137,298.257222101,
                AUTHORITY["EPSG","7019"]],
            TOWGS84[0,0,0,0,0,0,0],
            AUTHORITY["EPSG","6269"]],
        PRIMEM["Greenwich",0,
            AUTHORITY["EPSG","8901"]],
        UNIT["degree",0.0174532925199433,
            AUTHORITY["EPSG","9122"]],
        AUTHORITY["EPSG","4269"]],
    PROJECTION["Albers_Conic_Equal_Area"],
    PARAMETER["standard_parallel_1",29.5],
    PARAMETER["standard_parallel_2",45.5],
    PARAMETER["latitude_of_center",23],
    PARAMETER["longitude_of_center",-96],
    PARAMETER["false_easting",0],
    PARAMETER["false_northing",0],
    UNIT["metre",1,
        AUTHORITY["EPSG","9001"]],
    AXIS["X",EAST],
    AXIS["Y",NORTH],
    AUTHORITY["EPSG","5070"]]

The reason why your first attempt fails is because ESRI names the projection Albers, and PROJ.4 does not know that it is the same as Albers_Conic_Equal_Area.

If you want to build shapefiles from your Postgis database, I suggest to use the OGC WKT naming, not the ESRI one. Otherwise someone else will run into the same trouble as you.

Answer 3

The proj4txt unofficially seems to be "+proj=aea +lon_0=-96 +lat_0=23 +lat_1=29.5 +lat_2=45.5 +datum=NAD83" gathered from this link. For any future websurfer, here's the insert query I used:

INSERT into public.spatial_ref_sys (
srid, auth_name, auth_srid, proj4text, srtext
) 
VALUES ( 
95070, 
'<insert an identifier>', 
95070, 
'+proj=aea +lon_0=-96 +lat_0=23 +lat_1=29.5 +lat_2=45.5 +datum=NAD83', 
'PROJCS["USA_Contiguous_Albers_Equal_Area_Conic_USGS_version",GEOGCS["GCS_North_American_1983",DATUM["D_North_American_1983",SPHEROID["GRS_1980",6378137.0,298.257222101]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Albers"],PARAMETER["False_Easting",0.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",-96.0],PARAMETER["Standard_Parallel_1",29.5],PARAMETER["Standard_Parallel_2",45.5],PARAMETER["Latitude_Of_Origin",23.0],UNIT["Meter",1.0]]'
);