What is Flow Map?

A flow map is a thematic map that visualizes the movement of quantities (e.g. information or ideas, weather phenomena, people and other living things or physical objects) from one location to another, simultaneously indicating their amount.

It is commonly used to show the migration data and how it is distributed geographically.

The amount of migration in a particular flow line is represented by its size: the more thick the line is, the stronger the migration wave it stands for. Flow lines are drawn from a point of origin and branch out with arrows used to show the direction of movements. 

Flow map famous example

The best-known example of a flow map is Minard’s map of Napoleon’s disastrous Russian campaign of 1812.