Projection class

Some map projections can be visualized as true geometric projections directly onto the mapping plane—known as an azimuthal projections—or onto an intermediate surface, which is then rolled out onto the mapping plane. Typical choices for such intermediate surfaces are cones and cylinders. These map projections are called conical or cylindrical projections, respectively.

The azimuthal, conical, and cylindrical surfaces in the picture are all tangent surfaces, i.e. they touch the horizontal reference surface at one point (azimuthal), or along a closed line (cone and cylinder), only.

Cylindrical projection is best for a rectangular area and conic projection for a triangular area.