Sunday, December 8, 2013

PROPORTIONAL SYMBOL MAPPING IN GIS

  
 
 
Instructions:
Build a proportional symbol map (using a given base layer) in ArcGIS.

Methods:
The base map we were given contained information from the 2000 U.S. census. By opening the properties within the 'states' layer in the table of contents, I was able to open symbology at the top of the screen. From there I could choose any value from a dropdown menu to map. I also had to select proportional symbols under the quantities heading in accordance with the instructions.

I chose to make most of the map in ArcGIS. I was able to add my legend, title, and explanatory material directly from ArcGIS using the Insert dropdown menu. In order to make this map well,
I had to locate more type options similar to what you have in Word and Adobe Illustrator. By choosing customize at the top of the screen I was able to locate the draw toolbar. This gave me more aesthetic options to choose from.

Challenges:

Once I had selected proportional symbols and chosen to map the total Asian population in the 48 contiguous states, I had to choose the appropriate number of symbols to display in my legend and the min and max values for the correlating symbols. This required me to look at the values of each state and find the most meaningful number of classes. I then had to look at the symbol sizes in order to fit them appropriately to the size of my map.

When I built my legend, there were unhelpful headings included. I had to cover them with something. By selecting the box symbol in the draw toolbar I had pulled down, I was able to hide the material. I then drew my own Legend Headings over the top of my box.

After choosing my symbol sizes I noticed that symbols in Florida, Michigan, California, Idaho, Louisiana and New York were not visually centered to the eye. I did not see a way to move them in ArcGIS, so I exported the map as an Ai file to Adobe Illustrator. From there I was able to alter the location of my symbols.

However, this introduced a new problem. The Ai file did not transfer any of the typed material from ArcGIS. As a result, I tried exporting the file again as a PDF. After doing so the typed material was visible.

The last challenge had to do with the "Asian" classification used in the U.S. census. I felt a little uncomfortable with this terminology and did not want my map to leave a false reflection of myself as insensitive. I chose to include the formal definition the U.S. census provides for their terminology in order to explain why I used the term.

As I noticed in my previous chloropleth map, I needed to put in a light backdrop color in Adobe Illustrator rather than ArcGIS to keep that color from showing through the scale bar I had chosen to use.


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