Proportional symbol map
Also called: Graduated symbol map · Topic: Graphical Representation of Data and Thematic Maps · NCERT: Beyond NCERT
Meaning
A proportional symbol map draws a circle, square or sphere at a place. The symbol's size depends on the amount it stands for. It is also called a graduated symbol map. The key rule is that the symbol's area, not its radius, must match the value. So the radius goes up with the square root of the value (the cube root for spheres). It works best for amounts tied to points, such as cities or ports, where a dot map would become too crowded.
Example
On a map of India's largest cities, Mumbai, Delhi and Kolkata get the biggest circles. A city with four times another city's population gets a circle with twice the radius, because that gives four times the area.
Don't confuse with
- A dot map uses many dots of the same size and fixed value, spread inside each unit. A proportional symbol map uses one symbol at each place, sized to the total.