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)
Album of projections.
Last revision 1/18/2018