Projection Definition File

Orbit supports the Well Known Text Projection definition file (*.prj) as defined by the OGC, see OGC PRJ-WKT definition.
A prj file is a single line plain text file describing the coordinate system, its datum and, if applicable, the projection.

Prj files can be added as custom Orbit system CRS definition. A custom system CRS can be used to define the dataset CRS.
A Prj file won't be used if accompanied by the resource file itself to define directly the dataset CRS. In Orbit the EPSG code to define the datset CRS is saved in the Orbit Resource Descriptor.
More information about custom and dataset coordinate systems in Orbit, see Coordinate Reference Systems in Orbit.

Orbit supports the WKT prj file as defined by the OGC. Other prj variants of the “same” projection that are not supported by Orbit.

The OGC definition includes the TOWGS84 datum transformation parameters. The units of these 7 parameters are (meter,meter,meter,arc-sec,arc-sec,arc-sec,parts-per-million). The signs of the angles should be as the EPSG “Position Vector 7-parameter transformation” method (code 9606), not the “Coordinate Frame Rotation” method (code 9607).

More information see :

• Spatialreference.org
• OGC PRJ-WKT definition > 7.3.18 TOWGS84
• EPSG Guidance Note 7, Part 2

A lot of pre-defined Coordinate Reference Systems and Coordinate Transformations are accessible through the Orbit Software by using the EPSG Geodetic Parameter Dataset. However, the EPSG database does not record all possible geodetic parameters in use around the world. In addition to the pre-defined CRS in the EPSG database, OrbitGIS accepts custom CRS definitions by creating seperate PRJ-files.

http://spatialreference.org/ref/epsg/31370/

As it is :

PROJCS["Belge1972 / Belgian72",GEOGCS["Belge1972",DATUM["Reseau_National_Belge_1972",SPHEROID["International1924",6378388,297,AUTHORITY["EPSG","7022"]],TOWGS84[106.869,-52.2978,103.724,-0.33657,0.456955,-1.84218,1],AUTHORITY["EPSG","6313"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.01745329251994328,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4313"]],UNIT["metre",1,AUTHORITY["EPSG","9001"]],PROJECTION["Lambert_Conformal_Conic_2SP"],PARAMETER["standard_parallel_1",51.16666723333333],PARAMETER["standard_parallel_2",49.8333339],PARAMETER["latitude_of_origin",90],PARAMETER["central_meridian",4.367486666666666],PARAMETER["false_easting",150000.013],PARAMETER["false_northing",5400088.438],AUTHORITY["EPSG","31370"],AXIS["X",EAST],AXIS["Y",NORTH]]

Just to read more easily :

PROJCS["Belge 1972 / Belgian 72",
GEOGCS
[
    "Belge 1972",
    DATUM
    [
        "Reseau_National_Belge_1972",
        SPHEROID["International 1924",6378388,297,AUTHORITY["EPSG","7022"]],
        TOWGS84[106.869,-52.2978,103.724,-0.33657,0.456955,-1.84218,1],
        AUTHORITY["EPSG","6313"]
    ],
    PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],
    UNIT["degree",0.01745329251994328,AUTHORITY["EPSG","9122"]],
    AUTHORITY["EPSG","4313"]
],
UNIT["metre",1,AUTHORITY["EPSG","9001"]],
PROJECTION["Lambert_Conformal_Conic_2SP"],
PARAMETER["standard_parallel_1",51.16666723333333],
PARAMETER["standard_parallel_2",49.8333339],
PARAMETER["latitude_of_origin",90],
PARAMETER["central_meridian",4.367486666666666],
PARAMETER["false_easting",150000.013],
PARAMETER["false_northing",5400088.438],
AUTHORITY["EPSG","31370"],
AXIS["X",EAST],
AXIS["Y",NORTH]
]