Lab 5

Distance from Washington D.C. to KaBul
Mecator: 10112 miles
Stereographic: 9878

Distance from Washington D.C. to KaBul
Two Point Equidistant: 8341
Azimuthal Equidistant: 6648

Distance from Washington D.C. to KaBul
Bonne: 8329
Hammer_Aitoff: 6731

The six different maps above are six map projections containing different attributes. Map projection is a transformation that gives the 3-D world a flat face, which we can see in the maps above. Map projection can only hold certain different attributes for different use of a map. There are three preserved properties map projection, conformal, equidistant, and equal area. For different reasons of using a map, the properties that fit the requirement will be different leading to choose different type of projections. Conformal map projections preserved the local angles and shapes. Equidistant preserved the distance from a point to the center of Earth. Equal area preserved the proportional area on Earth. The maps above are distinguished by the different preserved properties each one has, not the types they are. Besides the preserved properties, map projection has three types, cylinder, plane, and cone.

The first two maps in the first picture are conformal, which means that the map have the same shape as the real world. As we can see in the Mecator map, each continent is the shape of the real world. On the other hand, the distortion is clearly shown in the map. The longitude is straight up near the north and south pole. However, as we know that the longitude should be come together as we close to the poles. It is more accurate near the equator than in the poles. As in the Stereographic map, the area of China is almost as big as Russia. Because of the distortion in the map, the distance from Washington D.C. to Kabul should have a difference between in the map and in the real world. The distance in the Mecator map, 10112 miles, and in the Stereographic, 9787 miles, comparing to the real distance, 6940 miles, has a significant difference.

The two maps in the middle are equidistant maps. The equidistant map does not mean that proportional the distance in the map is equal to the distance on ground. The equidistant means that the length for some particular reference points are preserved. The Two Point Equidistant map preserves the distance from any point on the map to two chose point. With different "control point" or the point people choose, the distance may be different. On the other hand, the distortion in the map is clear. The area of the Antarctica is obviously smaller. The Azimuthal equidistant map preserved the distance along the great circles radiating from the center. We can see how the continent shifted together with the distortion.    The difference between the real distance and  the distance on the map is not as large as the Conformal, giving more accuracy on the distance.

The last two maps are equal area. Equal area map projections preserved the proportional area of the ground. As we can see from the map, the large distortion of length and angles gives lots of errors of calculating the distance from Washington D.C. to Kabul. The other map has even more distortion. The heart-shape map changes the distance from one places to the other and the angles are clearly not preserved. With the distortions, the distance from Washington D.C. to Kabul may vary from one to the other. The six maps above show different preservation of certain property and the distortion of the maps, showing the importance of choosing the corresponding map for certain use.