Seven projections are currently available, these are:
Cylindrical
Mercator
Miller Cylindrical
Mollweide
Hammer Aitoff
Orthographic
Perspective
The currently displayed projection will be "greyed out" and not available for selection. Each of these projections (except the last) are described in the IDL mapping help and the user is referred to that document.
The perspective option is an extended orthographic option that allows the user to define a line as latitude,
longitude and altitude. It was primarly designed with the idea of displaying satellite orbits but may be used
with other data sets.