User scalable graduated circles with google maps

Abstract

The circle has long been a useful symbol for displaying quantitative data. Determining the proper size for the circles has remained a problem. If the circles are too small, differences in size are not readily apparent and a pattern is not evident. If the circles are too big, the overlap between the symbols will be excessive or too much of the map will be covered. A method is proposed here that allows the user to interactively adjust both the size and the opacity of the circle shading. The online version of the map, with all relevant code, is available at: http://maps.unomaha.edu/GoogleMapGallery/GradCircles/circles.htm