Lab Assignment #5

Lab #5 is all about the application of ArcGIS. We used ArcGIS in the last lab to learn the basic. In this lab, we use ArcGIS for map projections of the world. Map projection is any method that allow us to represent the surface of a sphere on a plane surface. To be simple, it allows us to represent a 3-D image to a 2-D image. There are many methods to project the earth. In this lab, there are 3 types of map projections. They are conformal, equal-area and equidistant. There are two examples showed under each map projections.

The first type of map projections are conformal. Gall Stereographic and Mercator projection are shown above. A conformal map means it preserves angle equally where the parallels and meridians are in perfect 90 degrees right angle. This kind of map will clearly display every landmass on the earth. However, since the conformal map projections preserve angle equally, the location and size of landmass on the maps and distance between them may be distorted. Conformal projection is not a good choice to measure the distance because that will be the distance will be much over than the actual distance.

Mollweide and Bonne projections are shown in above. They are the examples of equal area map projection. Equal area projections preserve the area or amount the space with features. For example, the area of Mexico and Greenland is similar. In the above example, the two territories are approximately the same size. However, equal area projections preserve area only. They distort all other properties such as shape, distance and direction. Equal area projections are useful in comparing the size or the area on a feature on the map.

 

The third type of map projections are equidistant. Equidistant conic and plate carree are two examples for equidistant map projections. Equidistant map projections preserve the distance between two points or the distance of a line on the map. That means when centered at any given point on the map that a straight line radiating from the center to any other point represents the shortest distance and can be measured to scale. Equidistant projection will only preserve distance on the map because area and shape will be distorted in the map.