Lab 5

This week's lab concerning map projections highlighted the various distinctions between conformal, equal area and equidistant map projections. The process of projection with ArcGIS proved to be quite simple, however provides an amazing amount of information regarding differences in map projections. This method ultimately elucidated aspects of map projections such as shape, appearance, area and distance. Taken as a whole, these differences shed light on the myriad of ways one can mathematically project the world and the inherent discrepancies in geographic interpretation associated with different projections.

In particular, the difference in shape of the map provides information about it's projection method. For instance, the Stereographic projection visible in the conformal map projections projects the world onto a plane with a shape of a circle. On the other hand, cylindrical map projections such as the Cylindrical Equal Area projection and the Equidistant Cylindrical projection project the map in a rectangular shape. These differences in shape can be traced back to method of projection: in the case of the Stereographic projection, a sphere is projected onto a flat plane whereas a cylinder is used the case of the cylindrical projections. As a result, the 30°x30° graticule layer present in all projections also has line shapes dependent upon the geometric object used in the projection process. As one can see in the aforementioned projections, the Stereographic map contains curved lines whereas the graticule lines remain at right angles in the cylindrical projections.

Furthermore, the differences in preserved properties between the maps is extremely striking. For example, when one compares the area of landmasses in a conformal projection such as the Mercator projection to an equal area projection such the Eckert IV, extreme area exaggerations are visible. More specifically, when one observes areas below the standard parallels in the Mercator projection (such as Antarctica), it is immediately apparent in the way area is distorted. Although in both conformal projections the areas above and below the standard parallels are grossly exaggerated, these projections do maintain consistent shape of landmasses.

In a similar manner, the comparison of distance between two points on the various map projections highlights significant discrepancies in distance. When calculating the distance between Washington D.C. and Kabul, Afghanistan using different projections one can come to completely different conclusions. For instance, the Cylindrical Equal Area projection provides a distance of approximately 10,000 miles whereas the Equidistant Cylindrical projection provides a distance of approximately 5,000 miles. Furthermore, even among equidistant projections there exists a significant difference due to the distinction between the point on the map from which distance is equidistant. In the case of the Azimuthal Equidistant Projection, distance is preserved originating from points at the poles, yet the Equidistant Cylindrical Projection originates from the standard parallel at the equator. This discrepancy in distance highlights the importance of utilizing map projections designed for regional distance calculations in order to maintain accuracy.