Lab 5 - Introduction to Projections


The purpose of this lab was to explore different coordinate projections. For the lab, I projected the counties of the state of Florida in three different coordinate systems: Albers, UTM 16 N and State Plane N. Upon visual inspection, the UTM and State Plane projections are slightly compacted and rotated counter clockwise when compared to the Albers projection. 

In order to see how this visual difference impacts the physical characteristics of the counties, I selected four counties distributed throughout the state – Alachua, Escambia, Miami-Dade and Polk – and compared their area in square miles. There are differences in area between the three projections for all counties. The greatest differences in area are for the two largest counties – Miami-Dade and Polk. In addition, the UTM projection has the biggest area difference for Polk County. From this analysis, I conclude that the UTM and State Plane distort the areas of some counties more than others, especially larger counties. The distortion could be a result of the way these projections are created. Both the UTM and State Plane projections are separated by zones and the zones might not connect together well without a distortion, especially for larger counties or ones outside the zone. This might be why the larger counties and the counties located more centrally and south like Miami-Dade and Polk, are the most distorted; perhaps they lie between or on opposite sides of the zones. Because of this and because Albers appears to be the projection preferred by FGDL, the Albers projection is most likely the best projection for the entire state of Florida. 

It is important to compare datasets in the same projections, because, as this exercise demonstrates, different projections of the same feature can distort characteristics of that feature. The results of spatial analyses on the same feature in different projections might not be true and might instead be a result of distortion created by the different projection.

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