Coordinate System Files
Concept Procedure
 
 
 

AutoCAD Map 3D uses certain files for storing coordinate system definitions and defining datum transformation information.

Following is a list of these files. Files that should not be modified are marked with an asterisk (*).

File Description
Agd66ToGda94.gdc Grid Data Catalog file for transformations within Australia. Default grid data files: Vic_0799.gsb, nt_0599.gsb, and TAS_1098.gsb. Default fallback datum: ASTRLA66.
Agd84ToGda94.gdc Grid Data Catalog file for transformations within Australia. Default grid data file: QLD_1299.gsb. Default fallback datum: ASTRLA84-7P.
GeoidHeight.gdc Grid Data Catalog file for determining the geoid height for any position in the United States. Default data files are GEO96AN.GEO, GEO96AS.GEO, GEO96HW.GEO, GEO96NC.GEO, GEO96NE.GEO, GEO96NW.GEO, GEO96PR.GEO, GEO96SC.GEO, GEO96SE.GEO, and GEO96SW.GEO. Fallback datum definition is not recommended.
Nad27ToNad83.gdc Grid Data Catalog file for transformations within North America. Default data files: Conus.l?s, Alaska.l?s, PrVi.l?s, Hawaii.l?s, STGEORGE.l?s, STLRNC.l?s, and STPAUL.l?s. Default fallback datum: NAD27-48.
Nad83ToHarn.gdc Grid Data Catalog file for transformations within North America. Default grid data files: alhpgn.l?s, azhpgn.l?s, cnhpgn.l?s, cohpgn.l?s, cshpgn.l?s, emhpgn.l?s, ethpgn.l?s, flhpgn.l?s, gahpgn.l?s, hihpgn.l?s, kshpgn.l?s, kyhpgn.l?s, lahpgn.l?s, mdhpgn.l?s, mehpgn.l?s, mihpgn.l?s, mshpgn.l?s, nbhpgn.l?s, ndhpgn.l?s, nehpgn.l?s, nmhpgn.l?s, nvhpgn.l?s, nyhpgn.l?s, ohhpgn.l?s, okhpgn.l?s, pvhpgn.l?s, sdhpgn.l?s, tnhpgn.l?s, uthpgn.l?s, vahpgn.l?s, wihpgn.l?s, wmhpgn.l?s, wohpgn.l?s, wthpgn.l?s, wvhpgn.l?s, and wyhpgn.l?s. Fallback datum definition is not recommended.
Nzgd49ToNzgd2K.gdc Grid Data Catalog file for transformations within New Zealand. Default grid data file: nzgd2kgrid9911.gsb. Default fallback datum: NZGD49-7P.
Rgf93ToNtf.gdc Grid Data Catalog file for transformations between the RGF93 and NTF datums used within France. Default grid data file: gr3df97a.txt. Default fallback datum: NTF-G.
Vertcon.gdc Grid Data Catalog file for computing the modeled difference in orthometric height between the North American Vertical Datum of 1988 (NAVD 88) and the National Geodetic Vertical Datum of 1929 (NGVD 29) for a given location specified by latitude and longitude. Default grid data files: VERTCONC.94, VERTCONE.94, and VERTCONW.94. Fallback datum definition is not recommended.
Category.csd * A binary compiled file used for storing coordinate system category definitions. Also called a dictionary file.
Coordsys.csd * Coordinate systems dictionary file.
Datums.csd * Datums dictionary file.
Elipsoid.csd * Ellipsoids dictionary file.
.mrt files * Multiple Regression Transformation binary files that store the coefficients required for multiple regression analysis. The base name of the file is the same as the key name of the datum with which it is associated.
.94 files * Grid data files used by Vertcon.gdc.
.geo files * Data files for determining the geoid height for any position in the United States. These are in GEOID96 format and are used by GeoidHeight.gdc.
.gsb files * Grid data files for Canada, Australia, and New Zealand. Both latitude and longitude shifts (as well as accuracy values) are incorporated into a single .gsb file. The file structure also supports the concept of multiple grids, and subgrids within a major grid.
.las and .los files * Grid data files for United States geography.
See Also