As noted by the documetation provided by the ACS Mapping Extension web site, ACS provides a margin of error that produces a confidence level of 90%. The first option, “Overlay CVs with Estimates,” will allow you to visualize the uncertainty of estimates at the same time as the estimates themselves. Mapping ACS Estimates with Coefficients of Variationġ) The tools are located under the “Mapping Data Uncertainty” option in the ACS Mapping toolbar. The following figure shows what my map looks like at this point. In this case, I chose the median income estimate and 5 total categories. Once you’ve set an output location, select “OK.”ģ) Finally, you will want to apply a symbology to the layer.
“CNTYIDFP” represents the FIPS code in the boundary file, and “GEO_ID2” is the corresponding code in the ACS table. In this figure, the first two fields indicate the items to be joined, one table to one shapefile.
In this example, I have downloaded county boundaries and county-level median income data from the 2005-09 ACS. With respect to boundary files, the TIGER 2008 county boundaries were used for this example.Ģ) Add the boundary layer to a blank map and select “Join ACS Table(s) with Shapefiles” option in the “ACS Mapping” toolbar. Follow these instructions to the letter and to their entirety. You will have a new “ACS Mapping” toolbar added to your window.ġ) The “Documentation” option in the “ACS Mapping” toolbar provides detailed instructions for downloading ACS data and boundary files. Once in this directory, select the “ACSMapping.tlb” file.Ģ) Before you leave the Customize window, be sure to check the “ACS Mapping Tools” toolbar.
Then select “Add from file…” and navigate to the installation directory.
In ArcGIS, select Customize from the menu bar, and click Customize Mode…. Detailed technical assistance is provided by the extension.ġ) Once you download the program, you will want to install and note the installation directory. This post provides a brief overview of installation, setup, and use. ACS Mapping Extensions is an ArcGIS addon available for both ArcGIS 9.3 and 10. A new extension provided by the Department of Geography and Geoinformation Science at Geroge Mason University enhances the mapping of ACS by data by allowing researchers to visualize both survey estimates while revealing the level of uncertainty in the estimates. The Census Bureau’s American Community Survey provides a continuous measure of the community demographics in the US.
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