Lab 5: Map Projections

Map projections are used to project the three-dimensional world on a two-dimensional scale with distortion. There are three types of the distortion to use depending on desired projection and use - equal area, equidistant, and conformal projections. Each projection will have pros and cons, but depending on the use, each brings a good amount of significance to GIS.

The equal area projections are used to preserve area but can distort distance. I used Behrmann and Bonne projections for equal area and I can see that the sizes of the countries in terms of area seem about right between the two maps. But just within the projections themselves, I can notice distortion on the lines on latitude. In the Behrmann projection, as I move away from the equator and towards one of the poles, there is noticeable difference of distance between each line of latitude. They distance is decreasing. A setback from the distortion of angles is quite obvious in the Bonne projection where as I move away from the Prime Meridian, the angles get more distorted more than the last time.

The equidistant projections are used to preserve distance, particularly between reference points. It must be noted though that the preserved distance only per projection. Each equidistant projection will vary with its distances between the reference points since there is a different distortion to each. So when measuring the distance between Washington D.C. and Kabul for the 2 projections I used, Equidistant Conic and Azimuthal Equidistant, the distances are different still since they are referenced elsewhere since there is over a 1000 mile-difference. Area can also be greatly distorted, like how in the Equidistant Conic projection, Antarctica looks greatly distorted by being very large.

The conformal map projections are used to preserve angles. Therefore, the projections can cause great distortion of areas. For example, when looking at the Stereographic projection, Australia looks incredibly large compared to the rest of the continents and countries which is mainly because of the distortion of the angles since the areas got so much larger as I would move away from the Prime Meridian. The distortion, at least when comparing the two projections I chose, did not make an enormous difference between the two distances.

After looking at my choice of map projections, it is hard to tell which projections would be best when measuring distance since of all the distortions. They do allow me to see the world in different spatial ways. It is safe to say that depending on what task must be done, there will be probably a different projection type needed.