### Custom Coordinate Reference System Definition

If QGIS does not provide the coordinate reference system you need, you can define a custom CRS.

To define a CRS, select Custom CRS from the Edit (Gnome, OSX) or Settings (KDE, Windows) menu. Custom CRS are stored in your QGIS user database. In addition to your custom CRS, this database also contains your spatial bookmarks and other custom data.

#### Define

To create a new CRS, click the New button and enter:

- descriptive name
- CRS parameters

After that you can save your CRS by clicking the button Save.

Note that the Parameters must begin with a +proj=-block, to represent the new coordinate reference system.

Defining a custom CRS in QGIS requires a good understanding of the Proj.4 projection library. To begin, refer to the Cartographic Projection Procedures for the UNIX Environment - A User's Manual by Gerald I. Evenden, U.S. Geological Survey Open-File Report 90-284, 1990. This manual describes the use of the proj.4 and related command line utilities. The cartographic parameters used with proj.4 are described in the user manual, and are the same as those used by QGIS.