This week's lab had us working with projections. The original file was shown in the Albers Equal Area, and from there, it was re-projected using the project tool to show the data in UTM 16 N and again in State Plane N. The next step in the process was to open the attributes table for each map to compare the area in square miles of four Florida counties: Escambia, Alachua, Miami-Dade, and Polk. Results in square miles are rounded to the nearest integer.
Having consistent projections for spatial analysis between
multiple data sets is important for ensuring that all data layers align
correctly when overlaid. This is also important for comparability, accuracy in
measurement, and accurate spatial alignment. In this lab, we were tasked to
compare three different projections (Albers, UTM 16 N, State Plane N)
for Florida Counties and note how they differed. The best projection for the
entire state of Florida is Albers. When compared with the other
projections (UTM 16 N, State Plane N), we can see that the area in
square miles differed the least in the more northern counties, Alachua and
Escambia, whereas the most notable differences can be seen in the southernmost
counties, Miami-Dade and Polk. This difference likely occurred because Escambia
is located within the coordinates of UTM 16 N and State Plane N and
Alachua can be found in the coordinates of State Plane N. Therefore, we
can see more distortion in counties such as Miami-Dade and Polk as they lie in
UTM 17 N and another state plane zone.
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The other portion of lab work this week had us using features of Arc GIS Online and then collecting data using Field Maps. Overall, it was a very simple process, but I liked this lab very much. I enjoy getting out into the field to collect data even if it is just in my neighborhood.
Link to the Web map is posted below.
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