Map projection has become a useful tool in geography because this as allowed people to recreate the spherical shape of the Earth in two dimensions. However, this process is not as simple as it seems. There are many different methods to map projection and each one distorts one aspect of the real world. Based on these distortions, map projections can be classified into three primary groups, conformal, equal area, and equidistant.
Conformal map projections are ones that maintain angular relationships and accurate shapes over small areas. This is important when angular relationships need to be maintained. The two examples used here are the Mercantor and Gall Stereographic. The Mercantor projection severely distorts size as you approach the poles. The Gall Stereographic is an improved version of the Mercantor projection which attempts to correct this distortion.
An equal area projection maintains accurate relative sizes which allows for accurate area calculations. This becomes important for maps that show distributions because the area needs to be accurate. The two examples used here are the Hammer projection and the Cylindrical Equal-Area projection. Both are variations of an equal area projection but are united in that they both preserve the area of the continents.
An equidistant map projection maintain accurate distances from the center of the projection or other points. The two examples here are the equidistant conic and sinusoidal projections. The conic projection has consistent spacement which creates a scale that is the same along all meridians. The sinusoidal projection is accurate across the Equator and the prime meridian.
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