Lab Assignment #5: Exploring Map Projections

Projections: Conformal, Equidistant, Equal Area

Distance: Between Washington D.C. and Kabul

Conformal Projections: 

Mercator, North Pole Stereographic

Distance: 10119 miles

Distance: 7634 miles

Equidistant Projections:

Sinusoidal, Equidistant Conic

Distance: 8098 miles

Distance: 6975 miles

Equal Area Projections:

South Pole Lambert Azimuthal, Bonne

Distance: 13530 miles

Distance: 6733 miles

            Since the earth is a spherical it is most correct to represent it as a three dimensional image. However, for many mapping purposes, especially in GIS, two-dimensional maps are necessary. All two-dimensional maps are projections with varying accuracy of shape, distance, and area. Conformal projections preserve angles, which make them ideal for navigation. Equidistant projections maintain distance between the origin and other points on the map. Equal area projections preserve areas and size of map features.

            Conformal projections are the most commonly used in most maps. The advantage of conformal projections is that angular relationships are preserved and can be used for navigation. A disadvantage is the distortion of sizes and areas. For example, Greenland is often portrayed as much larger in conformal projections than in reality. This is because distance and size become increasingly distorted when approaching the Polar Regions.

            Equidistant projections are most appropriate when distances are being measured between two points because distance is not distorted. However, the distances will only be preserved in certain conditions. For example the sinusoidal projection preserves distance along latitudes, which was ideal for measuring the distance between Washington D.C. and Kabul. Each equidistant projection has its own conditions for preserved distances, making the use of these maps very confusing.

            Equal area projections maintain the relative size and area of a geographic feature like a continent or country. Similarly to the equidistant projections, equal area projections cannot maintain relative size for all geographic features. Each equal area map preserves area in a certain region or with certain conditions. Therefore it is essential to choose the right equal area projection depending on your region of focus. For example, if you are interested in maintaining equal area in the North Pole region, the North Pole Lambert Azimuthal projection should be used.