Another application for a polar chart is for determining the amplitude of events happening within the boundaries of an area, where each event has its location determined with respect to the distance and direction it takes(any of the cardinal points) from a reference point.

This demo shows the effect of an earthquake over 4 cities using a polar bubble series. The center of each bubble is determined as mentioned above, and the diameter of each bubble reflects the amplitude of the earthquake relative to the Richter scale.