Example Standard Distance Center Plots
This image is an example of the kinds of output produced by the Wi-Fi visualization software packages GPSMap and kismet. These are wireless maps of three Chicago neighborhoods profiled in our photographic exhibit. Each network center is estimated using the mean center of multiple observations. A standard distance circle is then plotted around the center point, and red indicates that the signal is encrypted (WEP or WPA), while green indicates the signal is not encrypted. The box indicates our sample area. These images are interesting because they fail to visualize what you expect them to (e.g., the availability of Wi-Fi), and yet they are the standard output of this Wi-Fi visualization package.
For research on this topic, see How do we decide what the electromagnetic spectrum looks like?