Map projections are used to represent the surface of a sphere or another shape on a plane. They are critical in creating maps but it is important to note that they always distort the surface in some way. This distortion is very apparent by the difference in distance from Washington D.C. to Kabul, Afghanistan in the maps. Map projections are used to preserve many different properties of Earth, but not all of them at the same time. Each map projection I modeled (equal area, conformal, equidistant) acts to preserve specific properties and have unique applications.
Equal area attempt to preserve the area. Preserving area is essential for many important applications of maps: scientific information of geographic distributions (pollution, deforestation, crop yielding, etc...) and education atlases and charts. Equal area maps serve to display true area ratios that are hard to interpret from a table.
Conformal map projections preserve angles. They are usually used for large-scale applications; conformal maps are used in solving engineering and physics problems. They have been important in the study of the electromagnetic field, the gravitational field, and much more. They are generally better used for calculations than continental or world maps.
Equidistant map projections are used to preserve distance from a standard line or point. The distances are only correct between points along a straight line and otherwise are not accurate. Useful application are a polar projection, where all the distances from the center are measured along any longitudinal line will be accurate, to show airline distances, and for seismic and radio work.
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