You may have noticed that our digital maps catalog lists several maps that appear to be duplicates of each other. This is due to the fact that Digital Vector Maps offers maps in several varying styles, referred to in cartography as map projections. The term "map projection" refers to an attempt by cartographers to illustrate, or project our three dimensional earth onto a flat, two-dimensional surface. Depending upon how a cartographer wants a finished map to appear, or how accurately a cartographer wants to illustrate the various points on a map in relation to their actual three dimensional coordinates, a map maker can choose from any number of map projections. Following is a brief description of the different projections we offer with our vector maps.
The Robinson projection minimizes angular and area distortion. It is classified as a pseudo-cylindrical projection by reason of its straight parallels, along each of which the meridians are spaced evenly. The 'bulge' at the middle latitudes allows for equal areas. Rand McNally & Co. commissioned Arthur H. Robinson to create this map projection for world maps in 1961. See: Robinson Projection World Maps
The Mollweide projection was first published by mathematician and astronomer Karl Brandan Mollweide. It is a pseudo cylindrical projection meaning it preserves area and distances along the horizontals. Both the Equator and central meridian are standard lines, thus the whole map is twice wide as tall. The other parallels compress near the poles, while the other meridians are equally spaced at the equator. The meridians at 90 degrees east and west form a perfect circle, and the whole earth is depicted in a proportional 2:1 ellipse. See: Mollweide Projection World Maps
In 1906 the German professor Max Eckert published six pseudo cylindrical projections known as the Eckert projection. In all six proposals the poles are framed by a square, and the whole map by a rectangle twice as broad. The boundary meridians are simple curves. Additional features of the Eckert projection include: A central meridian that is straight, half as long as the Equator, and a standard line in odd-numbered projections, the poles are flat, half as long as the Equator, the even-numbered projections are equal-area and the odd-numbered projections have equally spaced parallels. See: Eckert Projection World Maps
The Gall's Stereographic projection is a cylindrical projection designed around 1855 with a perspective projection from two standard parallels at latitudes 45° N and 45° S. It is not equal-area, equidistant, or conformal. There is no distortion along the standard parallels, but it increases moderately away from these parallels, becoming severe at the poles. This projection was presented by James Gall in 1855. See: Gall Stereographic World Maps
WGS is an acronym for World Geodetic System which defines the shape and size of the ellipsoid of revolution that is considered to be the best mathematical model of the Earth. The latest revision is WGS 84 which was last revised in 2004. See: WGS 84 World Maps