What is a user-defined coordinate system?

The LLA and UTM coordinate systems are generally accepted coordinate reference systems worldwide. However, some states in the USA, such as Michigan, Mississippi and Oregon, adopt their own plane projection as a standard spatial reference for their state agencies to present their spatial data and maps. Other regions in the other countries may also have their own  spatial projection standards.

PC-GIS, PC-GPS and PC-MAPPER will let you define your own datum and enter the specifications for a projection plane  based on the Transverse mercator, Mercator, Oblique mercator, Lambert conformal conic, Albers Equal Area conic, Double Stereographic projection. The user-defined coordinate systems are stored in the file named user_cor.sys. You can add this file to the Document folder for the iCMTGIS or iGPSGIS via iTunes. Then your user-defined coordinate systems will become available in the iCMTGIS and iGPSGIS apps, and you may select one of them as the active coordinate system.


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