Map projections are an essential part of ArcGIS and the creation of complex and detailed maps. However, like all technology, there are both large benefits and potential pitfalls and inaccuracies to the features of the software. The main benefits arise from an increased amount of information available via the creation of 2D maps, whereas the main pitfalls are inaccuracies and limits to what projections can do.
The benefits of map projections are endless. First and foremost, they allow for the 3-dimensional earth to be viewed in 2 dimensions. This allows for a model of the earth to easily be folded up and carried around. Consequently, a road map can be carried with one in the car, a campus map can be carried with one around school, etc. It obviously would not be practical to always be carrying a globe or 3-dimensional projection of the earth around. Projections also allow the entire earth to be viewed at once, unlike on a globe, in which only around two-thirds of the earth can be viewed at once. In addition, map layers created by projections can be overlayed, and each layer can show different data. Consequently, large amounts of information can be shown on a single map.
However, no map projection is a completely accurate representation of the earth, and this is the main pitfall of projections. Map projections either distort the distances between locations on the earth, the areas of certain places on the earth, or the angles between different locations on the earth. Consequently, depending on the projection used, a country that in reality is larger than another country might appear to be smaller. Or, two locations that in reality are very far apart might appear to be fairly close to one another on the projection. Normally, a map projection can only preserve one of the three previous qualities (distance, area, or angles). However, even equidistant map projections don't completely conserve distance--distance is only conserved in a certain direction. In addition, if two maps stem from different projections, they cannot be layered on top of each other because boundaries between countries and features would not align properly.
Despite its inaccuracies, map projections comprise the core of cartography. Without them, maps would not exist. By using a combination of equidistant, equal area, and conformal projections, one can get a good idea of the layout of the earth. If a projection is used in combination with a globe, one can get an even better idea of the locations of the features of the earth. All in all, without map projections, many things we take for granted, such as GIS, road maps, and sailing the seas, would not be possible.
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