Shin Huoy's GIS Portfolio

Proportional Symbol Map

 

I was tasked to create a proportional symbol map of the 25 largest cities in China by population size. In a proportional symbol map, the area of the symbol is proportionate to the size of the variable. In this case, the area of the circles is sized in proportion to the population of the largest cities in China. 

 

There are two types of scaling methods in a proportional symbol map, absolute scaling and perceptual scaling.

 

When absolute scaling is applied, the sizes of the circles are directly proportionate to the size of the data. If the population size is twice as big in City A than in City B, the area of Circle A will be twice as big as well. 

 

As psychophysical research has found that people tend to underestimate areas, perceptual scaling utilizes a scaling factor that can be correctly interpreted visually by people.