Mapping

Map Projections
m_proj Initializes map projections info, putting the result into a structure
m_proj('set') tells you the current state
m_proj('get') gives you a list of all possibilities
m_proj ('get','proj name') gives info about a projection in the 'get' list.
m_proj ('proj name','property',value,...) initializes a projection.
In order to initialize a projection, you usually specify some location parameters
that define the geometry of the projection (longitudinal limits, central parallel,
etc.), as well as parameters that define the extent of the map (whether it is in a
rectangular axis, what the border points are, etc.). These vary slightly from
projection to projection. Two useful properties for projections are
(1) The ability the preserve angles for differentially small regions, and
Projections satisfying this first condition are called conformal
(2) The ability to preserve area.
Projection satisfying the second are called equal-area
No projection can be both. Many projections (especially global projections) are
neither, instead an attempt has been made to aesthetically balance the errors
in both conditions.