Projection properties

Projection Properties

The following projections have been implemented in this software:

	Plane	Cylinder	Cone	Azimuthal	Conformal	Equal area
Albers Equal Area Conic			x			x
Cassini		x
Equidistant cylindrical		x
Gnomonic	x			x
Hammer						x
Lambert Azimuthal Equal Area	x			x		x
Lambert Conformal Conic			x		x
Mercator		x			x
Mollweide		x				x
Orthographic	x			x
Polar Stereographic	x			x	x
Sinusoidal		x				x
Stereographic	x			x	x
UTM (Universal Transverse Mercator)		x			x
Van der Grinten		x

Geometrically, a projection can start from a plane, cylinder, or a cone.

The major properties desired in a map are:

Conformal: local angles and shapes are preserved; usable for navigation. Almost all serious, large scale maps are conformal (Mercator, UTM, and Lambert Conformal Conic).
Equal area: every region on the map represents the same area on the earth. Some maps used in GIS are equal area, like land cover, when the desire is to count pixels and compare categories.
Azimuthal projections map meridians as straight lines and parallels as complete, concentric circles. They are radially symmetrical. In any presentation (or aspect), they preserve directions from the center point. Great circles through the central point are represented by straight lines on the map. In GIS work, a projection would almost never be selected for its azimuthal properties, but note that the Lambert Azimuth Equal area and stereographic are coincidentally azimuthal but would be selected for conformality or equal area properties.

(see Snyder, 1987)

Last revision 1/18/2018