Coordinate Reference Systems

A coordinate reference system (CRS) is a coordinate-based local, regional or global system used to locate geographical entities.

CRS information can be viewed in the Select Coordinate Reference System dialog box.

Information in the dialog box is read from a interrelated set of files that control coordinate information.

These files are located in

C:\Program Files\CARIS\<application>\
<version>\system

The following table lists the files that define the CRS and datum transformations in CARIS. Many of these files can be copied and modified. The application can then be pointed to the modified files.

File	Description
`epsg.db`	A database file that contains EPSG coordinate reference systems and coordinate transformations developed by the International Association of Oil and Gas Producers (IOGP). CARIS supports the following CRS types from the EPSG database: Projected, Geodetic, Horizontal Compound, and Engineering. This file should never be modified. For more information on available Coordinate Reference Systems and transformations, see the IOGP website at http://epsg-registry.org/
`mapdef.dat`	The map definition file contains a list of CRS definitions. This file can be copied and modified. Do not modify the original file. For more information, see Map Definition File.
`datum.dat`	The datum file contains a list of ellipsoid parameters (semi-axes; X, Y, Z) and coordinate transformation parameters (shifts from and rotations about the geocentre) required to make the axis of the ellipsoid coincide with the WGS 84 ellipsoid. This file uses a Coordinate Frame Rotation transformation for datum transformations. The file can be copied and modified. Do not modify the original file. For more information, see Datum File.
`boundcrs.dat`	This file associates a CRS with a coordinate transformation methodology. The coordinate transformations can be defined in either epsg.db or datum.dat. For more information, see Transformation Linking File.
grid-shift datum transformations	Grid-shift datum transformations are a group of files that perform datum transformations. All grid shift files distributed with the application are located in this folder: `C:\Program Files\CARIS\Caris\<version>\system\GridShifts` Transformations are referenced through the Grid Shift Transformations setting in Tools > Options. Make sure that all grid shift transformation files are located in the folder referenced by this setting. For more information, see Grid Transformations.