Taxonomy of Data Visualization Methods - Data Visualization: A Successful Design Process - page 146

Dot plot map
Data variables : 2 x quantitative-interval.
Visual variables : Position.
Description : A dot plot map essentially displays a geographical scatter plot of
records, combining the longitude and latitude to position marks on the map.
In the following example, we also see this data being gradually plotted over
time to reveal a story of geographical spread:
Image from "Posted: Visualizing US Expansion Through Post Offices"
( http://blog.dwtkns.com/2011/posted/ ), created by Derek Watkins
Bubble plot map
Data variables : 2 x quantitative-interval, 1 x quantitative-ratio, 1 x categorical-nominal.
Visual variables : Position, area, color-hue.