The user will be prompted for the projection name. Most projections are supported. The PROJ.4 abbreviations for the names are used with two exceptions, viz. 'll', for latitude / longitude geographic co-ordinates, and 'stp', for the State Plane Co-ordinate system (used in the USA).
After the projection name, the user will be asked for a geodetic datum. If no datum transformation support is needed, the question may be answered with no, and no datum will be specified in the PROJ_INFO file. If this is the case the user must specify the ellipsoid (model of the curvature of the earth) to be used, otherwise it is determined by the datum being used.
If the datum or ellipsoid required are not listed within this program, the user/administrator may add the definition to the files datum.table, datumtransform.table and ellipse.table in the $GISBASE/etc/ directory.
Depending on the projection selected, the user will then be prompted for the various other parameters required to define it.
The projections of aea, lcc, merc, leae, leac, and tmerc will generate a request to the user for the prime meridian and standard parallel for the output map.
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