Lab 5: Projections in ArcGIS

For this Lab, I created 6 maps with different projections. 2 are Equal area, 2 are equidistant and 2 are conformal(preserving angles). For each of these maps I measured the distance between Washington D.C. and Kabul, Afghanistan. The shear amount of difference in the distance measured clearly shows that one must always keep in mind what they are trying to accomplish with the map when deciding on a projection.

Each map has certain distortions because no 2-d map can accurately represent our 3-d world. When going from a 3-d model to a 2-d model, a projection is used. Each projection is good at accurately mapping a specific property. As the name implies, Equidistant projections retain distances. When you know you will use a certain map for measuring distances, then it would be prudent to use a Equidistant projection. If you will measure area, then an Equal-area projection should be used. A conformal map is used when the map will be used for navigation or when angular relations must be preserved.

In addition to choosing the projection type, there are also other considerations. It is important to consider the "center" of the map. The most accurate part of a map is where the projection shape is the closest or overlapping with the 3-d world. So different types of projections have different centers or areas of focus. Choosing a projection that distorts the area of interest the least is very important to consider.

If one does not choose a projection wisely, the information from the map will be worthless. The data can be extremely skewed without a good projection. It is important to think about the use of the map and the area it will be displaying so the right type of projection, of the right geographic region, will be used.