Pitney Bowes MapInfo Professional - Manual (Page 480)

False Northings and False Eastings
Calculating coordinates is easier if negative numbers are not involved. To eliminate this problem in
calculating State Plane and Universal Transverse Mercator coordinates, it is common to add measurement
offsets to the northings and eastings. These offsets are called False Northings and False Eastings. They
are expressed in coordinate units, not degrees. (The coordinate units are specified by the Units parameter.)
Range (Azimuthal Projections)
The range specifies, in degrees, how much of the earth you are seeing. The range can be between 1
and 180. When you specify 90, you see a hemisphere. When you specify 180 you see the whole earth,
though much of it is very distorted.
Polyconic Projection
The following description is copied from "Map Projections - A Working Manual", USGS Professional
Paper 1395, by John P. Snyder.
The Polyconic projection, usually called the American Polyconic in Europe, achieved its name because
the curvature of the circular arc for each parallel on the map is the same as it would be following the
unrolling of a cone which had been wrapped around the globe tangent to the particular parallel of latitude,
with the parallel traced onto the cone. Thus, there are many ("poly-") cones involved, rather than the
single cone of each regular conic projection.
The Polyconic projection is neither equal-area nor conformal. Along the central meridian, however, it is
both distortion free and true to scale. Each parallel is true to scale, but the meridians are lengthened by
various amounts to cross each parallel at the correct position along the parallel, so that no parallel is
standard in the sense of having conformality (or correct angles), except at the central meridian. Near
the central meridian, distortion is extremely small.
This projection is not intended for mapping large areas. The conversion algorithms used break down
when mapping wide longitude ranges. For example, WORLD.TAB, from the sample data shipped with
MapInfo Professional, may exhibit anomalies if reprojected using Polyconic.
Equidistant Cylindrical Projection
The Equidistant Cylindrical projection (also called the Equirectangular projection, geographic projection,
Plate Carrée, or Carte Parallelogrammatique projection or CPP), is a very simple map projection attributed
to Marinus of Tyre, who Ptolemy claims invented the projection about 100 AD.
The projection maps meridians to equally spaced vertical straight lines, and circles of latitude to evenly
spread horizontal straight lines. The projection is neither equal area nor conformal. Because of the
distortions introduced by this projection, it has little use in navigation or cadastral mapping, and finds its
main use in thematic mapping. In particular, the Plate Carrée is used often in computer applications that
process global maps, because of the particularly simple relationship between the position of an image
pixel on the map and its corresponding geographic location on Earth. The Plate Carrée (French, for "flat
square"), is the special case where standard parallel is zero.
The following examples are of PRJ entries for Plate Carrée and Equidistant Cylindrical projection centered
at 46.5 degree Standard Parallel (used in France):
"Plate Carree WGS84", 33, 104, 7, 0, 0, 0, 0
"Equidistant Cylindrical 46.5 Degree WGS84", 33, 104, 7, 0, 46.5, 0, 0
MapInfo Professional 12.5 480
Projections and Their Parameters