Flow maps are a kind of thematic map used in cartography to demonstrate
the movement of objects between unalike areas. These types of maps can show
things like the movement of goods across space, the number of animal species in
a specific migration pattern, as well as traffic volume and stream flow. They
can also display both qualitative and quantitative data. Flow maps usually
represent the movement of goods, weather phenomena, people and other living
things with line symbols of different widths. Thus, the use of flow lines on a
flow map is comparable to the use of graduated symbols on other types of
thematic maps. These lines are often used to show migration, trade and other
intercourse between areas.
