Lab#5: Projections in ArcGIS

Map projections are unique ways of representing the surface of the Earth or some parts of the Earth on a flat surface such as a map or a computer screen. They greatly enhance the graphics and convey the information in distinctive manners. Since flat surfaces cannot fully convey the actual shape and grooves of the Earth, we must utilize distortions to try to have a better understanding of the Earth. We can use elements like “conformality”, distance, direction, scale, and area to distort the Earth’s surface to better meet the different ways we can look at the Earth’s surface. With distortions, there exist many inaccuracies but map projections help to put less emphasis on these errors and more on the specific method of projecting the Earth’s surface. This simply means that distortions are obviously not perfect and many of them are efficient projections of the Earth’s surface, however, determining the most effective type is significant. For this assignment, I will focus on the three types of projections: conformality, distance, and area.

Essentially, conformality is the specific scale of a map where any point on the map is the same in all directions. This is also called “conformal”. This is when the Meridians, which are longitude lines and the parallels, the latitude lines, intersect to form right angles. The shape of the Earth is preserved locally on these types of maps. I used the Mercator and Gall Stereographic map projections, two examples of conformal map projections, to portray the Earth’s surface. The most distinguishable “errors” on these maps are the following: Antarctica’s surface area seems much larger compared to the rest of the Earth; most of the area for all of the continents seen on the map is misleading because Africa seems to have similar surface areas as North and South America; both the Mercator and Stereographic projections generated similar distances between Washington D.C. and Kabul.

An equidistant map portrays distance in a way that it is the same from the center of the projection to any points on the map. While conformal preserve the shape of the Earth locally, equidistant maps preserve distances along the parallels of different places on the map. I used the Equidistant Conic and Sinusoidal styles for equidistant projection. These are two significant ways of transmitting information because the Equidistant Conic projection distorts the direction, area, and shape away from the standard parallels and instead, portray those areas that are near to and on one side of the equator, which means that the central meridian or the equator are not altered. The Sinusoidal projection is an important tool because the north-south and east-west scales are the same everywhere from the central meridian. Interestingly, the distance on the map between two parallels is smaller than the distance between the two points on the same meridian.

Equal-area maps look at areas throughout the entire map in order for all the mapped areas to have the same proportional relationship to the areas on the Earth that they represent. Even though the projections that I used, the Mollweide and World Hammer-Aitoff, are visually very similar, there is a slight difference where the Mollweide projection has straight parallels of latitude but the Hammer displays curved ones. Hence, it is important to notice that they are both pseudocylindrical map projections generally used for aerial, global views of the Earth. These projections leave out accurate measures of angle and shape in order to display the truest depiction of area. The equator is shown as a straight horizontal line and perpendicular to a central meridian, only half the length of the equator. The other parallels are compressed near both poles while the meridians are spaced equally around the equator and form a perfect circle at 90 degrees east and west.