Lab 3: Projections

 

This map contains three data frames showing three different projections: Albers, UTM, and State Plane N for the state of Florida. It also includes a table showing the area calculations for Alachua, Escambia, Miami-Dade, and Polk Counties. Some of the counties had a larger difference in area between the three projections. Escambia has the least difference in area while Miami-Dade had the most. It seems the further east the county area is located within the state of Florida, the greater the difference in area between the projections. The Albers and State Plane N differed the most by 12.16 square miles in Miami-Dade. The second greatest difference was between Albers and UTM 16 N in Polk county by 11.97 square miles. It seems like it depends on the location of the county in the state. Specifically, where it lands in east-west direction will determine the largest differences in area between Albers, UTM 16 N, and State Plane N projections.

I downloaded the Florida counties data from the US Census Bureau on FGDL.org. To begin the project, I went into the Settings and changed the base map so that the Web Mercator projection would not interfere when comparing the other projections. Using the Toolboxes I chose Data Management Tools, Projections and Transformations, and Project to input the counties data in Albers coordinate system to UTM and then State Plane N coordinate systems.  To find the different county area in square feet for each coordinate system, I use the calculate geometry attribute feature in the Geoprocessing Pane. The area populated in the attribute tables and from there I could create the table that is shown in the map above and analyze the differences in area from each coordinate system.