Map projection is a systematic representation of a spherical body, such as the Earth, in a flat (planar) surface. Each map projection has specific properties that make it suitable for specific mapping needs. Parameters defined by map projection constitute a function used to convert points from latitude and longitude to Cartesian coordinates.

The three principal types of developable (flattenable) surfaces: planar on the left, conic in the middle, and cylindrical on the right. These are all shown in the tangentable case (touching the globe at a point or along the line). The secant case results when the conformable surfaces cuts the globe, instead of touching it.

Following map projections are supported:

• Conic projection - map projection in which the surface of the Earth is drawn as it would appear if projected on a cone wrapped around the earth. The Lambert Conformal Conic is often used for maps of the continental United States, France, and other countries.
• Cylindrical projection - map projection, in which the surface of the Earth is drawn as it would appear if projected on a cylinder wrapped around the earth in a north-south direction.
• Equidistant projection - map projection showing true distances only from the center of the projection or along a special set of lines. No flat map can be both equidistant and equal area.
• Mercator projection - map projection, designed by Gerhardus Mercator, in which the surface of the Earth is drawn as it would appear if projected on a cylinder wrapped around the earth.
• Transverse cylindrical projection - map projection, in which the surface of the Earth is drawn as it would appear if projected on a cylinder wrapped around the earth in an east-west direction.
• Universal Transverse Mercator (UTM) projection - a specific implementation of the Mercator projection, designed for use around the world.

Projection Origin

The origin of rectangular coordinates for a map projection. For example, the longitude origin of a conic projection is the line of longitude that is straight and perfectly vertical. This longitude value can be converted to an X-coordinate of zero, and is usually specified as the center of the map. The latitude of the projection origin is often the nearest round number that is south of the southernmost extent of the region to map.

False Origin

When the central meridian bisects the mapping region, half of the X coordinates are negative values. An offset called the false origin can be added to all coordinates to make them positive. The X coordinate of this offset is called the false origin easting. The Y coordinate of this offset is called the false origin northing.

Scale Reduction Factor

To produce the smallest possible distance between the projection surface and any point in the region you are mapping, you must specify a scale reduction factor. This is particularly important when you are mapping large regions.

Quadrant

One of the four regions defined by the axes of a Cartesian coordinate system. Quadrants are numbered counterclockwise, one through four. Numbering begins with the quadrant in which both the x- and y-coordinates are positive (usually the upper-right quadrant).

Useful Range Parameters

The minimum and maximum latitude and longitude for which a coordinate system is considered valid.