Lab #5: Projections in ArcGIS

In this lab, I created six different projections in ArcGIS to explore the different properties of projection techniques and understand how it affects the mapped distance between two cities. The projections above each have at least one of the following properties: equal area, equidistant, or conformal. The equal area property ensures that all land masses have area equal to their true area on Earth. Equidistant instead preserves the distance over the map and will match the true distances on Earth. Conformal maps will preserve the shape of all land masses and should match their true shape on Earth. It is not necessary for each map to have more than one of these properties, but some will have multiple.

The first two maps shown are the equal area projections. I used the cylindrical and Bonne projections to create these maps. Equal area projections are most useful for geographic studies that rely on the area of a certain land mass or body of water. If the study is focused on finding the area of different lakes, then this type of projection would be most effective for the project. Note that this type of projection can distort the shape of the Earth as shown in the Bonne projection. This non-conformal map might be inadequate for some types of studies. However the cylindrical projection preserves the shape and is conformal, giving it an advantage as it more closely represents the true Earth.

The second two maps present an equidistant projection of the Earth. I used the sinusoidal and conic projections to make these maps. They are most useful for measuring precise distances or mapping buffer zones around an object of interest. Note that both maps distort the shape and area of the continents. When measuring the distance between the two cities of interest, I found that their distances differed significantly. I believe the error was due to the path of measurement tool used to measure the cities. For the conic projection, the measurement path curved in an arc over the Earth's surface, crossing over the top of the Earth as if a plane was flying north east. On the other hand, the sinusoidal projection had the measurement use a more straight and direct path. I believe this caused the measurement to be shorter on the sinusoidal projection.

The last two map projections, the Mercator and Miller cylindrical, mapped the Earth while preserving the shape of all land masses and bodies of water. This type of projection has fewer uses for making quantitative measurements. However it is still important for making maps in which the user expects to see familiar shapes of states or countries. It may also be useful for navigation since a guide map should accurately represent the shape of the trail, road, or state. Note that in all of these projections, the differences in distance between the two cities is quite large. However in most cases, map projections are only used over a small portion of Earth and do not need to represent huge areas. Projecting a small area will make these differences much less obvious and errors will be less significant. Overall I have a better understanding of projections and how they can be used to make the most effective map for any specific project.