Using Projections and Coordinate Systems

The default coordinate system is longitude and latitude. The following GISDK functions include a Projection option for specifying another coordinate system when importing into or exporting from a geographic file:

The Projection option takes two parameters:

• A string containing the projection specification, which identifies the projection or coordinate system

• An array of option strings.

A large number of standard coordinate systems are supported, including State Plane Coordinates for NAD27 and NAD83 in the U.S., and coordinate systems for countries all over the world. A standard coordinate system is based on a pre-defined projection, so you only need to specify the coordinate system.

A large number of projections are also supported, including Universal Transverse Mercator (UTM) and Gauss-Kruger, both of which have defined coordinate system zones. For other projections, you can define a custom coordinate system. The definition can specify an ellipsoid.

You can use the Transform option with the Projection option to correct coordinates that may have been modified from their standard form (e.g., 1,000,000 subtracted to save storage space).

The following sections describe how to use:

• Standard coordinate systems

• Your own coordinate systems

• The UTM projection with a coordinate system zone

• The Gauss-Kruger projection with a coordinate system zone

• Other projections with a custom coordinate system

• Units of measure

• Ellipsoids, with a list of the ellipsoids used by common datums

• Transformations

• Datum conversions, between U.S. and other datums

• Projections as settings for maps

See "Projections and Coordinate Systems" in the Maptitude Help for further information.