In this lab, we learned to create maps with different types of projections. The software that was used was ArcMAP, which we practiced to use last week in lab 4. Because the earth is spherical it is impossible to map every aspect of the planet correctly, and every projection of the globe has a “flaw” so to speak. That is why there are hundreds of types of map projections, and 66 that ArcGIS supports. There are three main categories of map projections: conformal, equal area, and equidistant. Usually one can choose a map from one of the categories based on which aspect of the map is more important.
The first type of projection that will be discussed is conformal. In order for a map to be conformal, it must have right angles, or 90 degrees, between every parallel and meridian. In order to have right angles at every intersection, conformal map projections usually sacrifice straight lines and area. For example, Greenland’s size on conformal maps is much larger than in reality because size becomes distorted near the north and south poles.
Equal area map projections, as it says in the name, maintain a relative size at every location on the map. The aspects that they lose are angles and distance. If one would like to compare population versus country size on a map, an equal area map projection should be used. It is interesting seeing the size of Antarctica on an equal area projection compared to it on a conformal projection.
The third type of projection is equidistant, which keeps an accurate relative distance between points on a map. It is most useful when trying to find how far one place is from another. The drawbacks of equidistant maps are their inability to keep correct area and angles. Also, equidistant maps usually only preserve distances under certain conditions, so it can be difficult to use the maps.
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