Why are most large-scale maps conformal?
At large scales, a conformal projection centered on the area of interest produces insignificant errors in distance and area. These errors are often smaller than what D.H. Maling, author of Coordinate Systems and Map Projections, calls the “zero dimension”the point at which projection distortion is less than the error caused by physical properties of the map (paper shrinkage, pen width, and so on). “Large-scale” is not an exact term, but in this context it should hold for scales of 1:100,000 or larger. It may also apply to smaller scales if the area of interest has a compact shape. For example, Maling says that the area distortion in a 1:500,000 Transverse Mercator projection of England is trivial. Maps that preserve area On an equal-area projection, the size of any area on the map is in true proportion to its size on the earth. You should use equal-area projections to show: The density of an attribute with dots (for example, population density) The spatial extent of a categorical attri
