Arthur H. Robinson credited Henry Drury Harness with the first map to clearly attempt to portray point sizes proportionally, on an 1838 map of cargo traffic in Ireland (with See more

The primary goal in selecting a point symbol to use in a proportional symbol map is that users should be able to accurately judge sizes, both in comparison to the legend to … See more

Most proportional symbol maps will have occasional overlap between symbols, typically around the largest symbols or in regions with a high density of features. This can lead to errors in size interpretations, and when a mass of symbols obscures … See more

Proportional symbol maps represent a set of related geographic phenomena (e.g., cities) as point symbols. These point locations can have … See more

The second part of the proportional symbol map is the choice of variable to represent by symbol size. The best variables to use in this technique are … See more

Theoretically, the proportional symbol map works because the "size" of the symbol appears to be proportional to its value, with size generally … See more

The primary purpose of the legend for a proportional circle map, as with any thematic map, is for the map reader to clearly understand … See more