3

I was looking into PostGIS and its defined Spatial Reference Systems, and I found that some have no proj4.
Why don't they?

SELECT auth_name || ':' || auth_srid, proj4text FROM spatial_ref_sys ORDER BY proj4text

"EPSG:22300";""

"EPSG:29701";""

"EPSG:3577";"+proj=aea +lat_1=-18 +lat_2=-36 +lat_0=0 +lon_0=132 +x_0=0 +y_0=0 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs "

5

Gdalsrsinfo gives a hint:

gdalsrsinfo epsg:22300

PROJ.4 : ERROR 6: No translation for Tunisia_Mining_Grid to PROJ.4 format is known.
''

OGC WKT :
PROJCS["Carthage (Paris) / Tunisia Mining Grid",
    GEOGCS["Carthage (Paris)",
        DATUM["Carthage_Paris",
            SPHEROID["Clarke 1880 (IGN)",6378249.2,293.4660212936269,
                AUTHORITY["EPSG","7011"]],
            TOWGS84[-263,6,431,0,0,0,0],
            AUTHORITY["EPSG","6816"]],
        PRIMEM["Paris",2.33722917,
            AUTHORITY["EPSG","8903"]],
        UNIT["grad",0.01570796326794897,
            AUTHORITY["EPSG","9105"]],
        AUTHORITY["EPSG","4816"]],
    PROJECTION["Tunisia_Mining_Grid"],
    PARAMETER["latitude_of_origin",36.5964],
    PARAMETER["central_meridian",7.83445],
    PARAMETER["false_easting",270],
    PARAMETER["false_northing",360],
    UNIT["kilometre",1000,
        AUTHORITY["EPSG","9036"]],
    AXIS["Easting",EAST],
    AXIS["Northing",NORTH],
    AUTHORITY["EPSG","22300"]]

Or:

gdalsrsinfo epsg:29701

PROJ.4 : ERROR 6: No translation for Laborde_Oblique_Mercator to PROJ.4 format is known.

Message means that some tranformations which are used in EPSG datebase are not implemented in Proj.4.

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