Retrieving point coordinates
If the coordinates of point(s) of interest are already available, this step can be skipped. If not, the first step is to retrieve the coordinates of the geographic center of any standard area (any area available from the Pick Geography tab). This is done by performing the following steps. First, click the Pick Geography tab and select area(s) of interest. Next, click the Simple Variables tab and then expand the Geographic Identifiers folder by clicking the + sign to the left. Select the variables Internal Point (Latitude) and Internal Point (Longitude). Generate file or report output from the Output tab.
Use the output report to copy and paste the latitude and longitude into the dialog box that appears after choosing "Add Radii". Below is an example of an output report.
Create radii for a point
Click the Pick Geography tab and then the File button. Next, select "Add Radii"
Enter the coordinates (internal points) for one point in the "Create a Point" window as shown below.
Enter desired radii.
The nonstandard area(s) just created will be added to the Pick Geography menu. Summary data for these area(s) can now be retrieved.
Additional notes
The smallest unit of standard geography available (see below) is used to generate data for each radius. The accuracy of data generated for a radius tends to increase as the standard unit of geography used becomes smaller. Accuracy also increases as the radius becomes longer. Data generated for a small radius (e.g. one mile) by using any data set other than Summary File 1, usually produces the most inaccurate estimates.
| Data Set | Smallest geographic unit |
|---|---|
| Summary File 1 | block |
| Summary File 2 | census tract |
| Summary File 3 | block group |
| Summary File 4 | census tract |
| Summary File 1 National File | census tract |
| Summary File 3 National File | census tract |
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