Map Projection
Map projection is the method of transforming the three-dimensional sphere onto plane maps. There are many different types of map projection. Among these types, there are three kinds of projections are being used commonly – equal-area projection, equidistant projection, and conformal projection. In fact, none of the projections can transform a map perfectly; they can only preserve certain properties, such a distance, proportion, and area, accurately.
Equal-area projection is a projection that keeps the size of areas equally with correct proportion. Albers conic, Mollweide, Lambert amimuthal equal-area, Hammer-Aitoff, Bonne, and sinusoidal are examples of equal-area projections. In this exercise, I have choosen Hammer-Aitoff and Bonne. Hammer-Aitoff projection to shows the Earth as an ellipse; Bonne projection is a pseudo-conic projection.
Equidistant projection is a projection that maintains same distances at some reference points. An equidistant projection map is distances from the center of the projection to any other place on the map are uniformin all direction. Azimuthal equidistant, plate carree, two-point equidistant, and soldner are some examples of equidistant projections. I chose Azimuthal equidistant and plate carree projection in this assignment. Azimuthal equidistant projection uses center point of the map as a reference point; therefore, its information is accurate. The other one I chose, the plate carree projection, also called the equirectangular projection, preserves distances on all longitudes.
Conformal projection is a projection that preserves the correct angle and shapes. In a conformal projection, parallels and meridians intersect at right angle. A conformal projection maintains equal angles at each point, including those between the intersections of arcs; therefore, the size of areas enclosed by many arcs may be greatly distorted. Conformal projections include Roussilhe, Mercator, stereographic, and Lambert conformal conic. I chose Mercator and stereographic to project my maps. Mercator projection projects the world using cylindrical map projection which means the portion that near the equator is more accurate; while stereographic projection preserves angles.
In this assignment, we need to create six different projections in order to see the differences of distances between Washington, D.C. and Kabul, Afghanistan among different projections. After comparing all six maps, I realized that projections that are belong to same types of maps, the distances between Washington, D.C. and Kabul, Afghanistan varies. Hence, it is very important to choose the appropriate maps to present information as different kinds of map projections provide different accuracy of measurements because of distortion. The actual straight line distance between Washington, D.C. and Kabul, Afghanistan is 6923.39 miles, so the most accurate projection for measuring distance is Boone projection, which display 6730.70 miles. On the other hand, the other maps have about 3000 miles of differences to the actual distance.
Map projection is the method of transforming the three-dimensional sphere onto plane maps. There are many different types of map projection. Among these types, there are three kinds of projections are being used commonly – equal-area projection, equidistant projection, and conformal projection. In fact, none of the projections can transform a map perfectly; they can only preserve certain properties, such a distance, proportion, and area, accurately.
Equal-area projection is a projection that keeps the size of areas equally with correct proportion. Albers conic, Mollweide, Lambert amimuthal equal-area, Hammer-Aitoff, Bonne, and sinusoidal are examples of equal-area projections. In this exercise, I have choosen Hammer-Aitoff and Bonne. Hammer-Aitoff projection to shows the Earth as an ellipse; Bonne projection is a pseudo-conic projection.
Equidistant projection is a projection that maintains same distances at some reference points. An equidistant projection map is distances from the center of the projection to any other place on the map are uniformin all direction. Azimuthal equidistant, plate carree, two-point equidistant, and soldner are some examples of equidistant projections. I chose Azimuthal equidistant and plate carree projection in this assignment. Azimuthal equidistant projection uses center point of the map as a reference point; therefore, its information is accurate. The other one I chose, the plate carree projection, also called the equirectangular projection, preserves distances on all longitudes.
Conformal projection is a projection that preserves the correct angle and shapes. In a conformal projection, parallels and meridians intersect at right angle. A conformal projection maintains equal angles at each point, including those between the intersections of arcs; therefore, the size of areas enclosed by many arcs may be greatly distorted. Conformal projections include Roussilhe, Mercator, stereographic, and Lambert conformal conic. I chose Mercator and stereographic to project my maps. Mercator projection projects the world using cylindrical map projection which means the portion that near the equator is more accurate; while stereographic projection preserves angles.
In this assignment, we need to create six different projections in order to see the differences of distances between Washington, D.C. and Kabul, Afghanistan among different projections. After comparing all six maps, I realized that projections that are belong to same types of maps, the distances between Washington, D.C. and Kabul, Afghanistan varies. Hence, it is very important to choose the appropriate maps to present information as different kinds of map projections provide different accuracy of measurements because of distortion. The actual straight line distance between Washington, D.C. and Kabul, Afghanistan is 6923.39 miles, so the most accurate projection for measuring distance is Boone projection, which display 6730.70 miles. On the other hand, the other maps have about 3000 miles of differences to the actual distance.
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