US Counties Map with State Outlines
This week we are working with ArcMap to create a map of US census data by county. ArcMap is the main component of ESRI's ArcGIS suite of geospatial processing programs, and is used primarily to view, edit, create, and analyze geospatial data. ArcGIS is a massive and complicated program, one of the largest programs ever written. It represents a major area of employment for geography students, as can be seen from this Google Map of jobs in the US. We will delve into the program simply to make the required maps and save them to Illustrator format.
Before you start, download the associated Shapefile and unzip.
We will be using ArcMap through Amazon Web Services. The local program to access the ArcMap instance is Microsoft Remote Desktop.
Steps Part I in ArcMap:
- Once the map is uploaded and displayed, you'll see that it needs to be projected. We will use the conic equal area projection, and we'll eventually need to do this three times for each of the following - a) contiguous US; b) Alaska; c) Hawaii. Each of these files will need to be saved separately.
- The associated data is from the 2010 US Census. The first thing to do is choose one of the available census data values. You should be able to find the same data that you classified with Excel.
- Does it need to be normalized? Most of the data needs to be divided by the total population of each county. This is called normalization and creates a percentage. In this assignment, normalization can be done directly in the data classification dialog.
- Classification: Notice how the method of classificaiton affects the resultant map and the visible distribution.We don't have standard deviation classification method based on the chi-square but all of the other methods that we did in Excel are there. Decide on a method that "best" represents your selected data.
- Number of categories: Use 5. Remember that more categories leads to a less-generalized map.
- Add the US states layer that makes a thicker line around each state. These thicker outlines helps to interpret the map. You'll need to apply hollow to each state polygon.
- The legend editor is a complicated and stupid piece of software. Make sure you make a legend of the counties, not states, and select the default answer in all of the dialogs that follow. You'll need to re-create most of the legend in Illustrator, at least the numbers.
- Save a US48.ai, Alaska.ai, and Hawaii.ai.
Steps Part II in Illustrator:
- Open the three files, release the mask, and ungroup (Object menu).
- Make all state polygons empty.
- Open three counties files, unmask, and ungroup.
- Use the 48-county file as your base. Copy and paste Hawaii and Alaska. Resize to fit in left corner.
- Create legend boxes, title, source, name, classification method.
- Select all polygons of the same color and reshade based on ColorBrewer.
- Complete shading of legend. Add neatline. Add a white rectangle around the map to make the neatline visible in the PNG version.
- Post on your website as PNG and PDF.