Cartisan > Types of Maps > Flow Maps

Flow map is a cartographic category that refers to a type of map that uses arrows or linear features to depict a size and direction of a variable (vectors). The name is a reference to watershed analysis, from which the basis is formed by direction of water movement, origin and destination of said water, and how much water has accumulated. Below is an example created by out cartographers.

For this map it was decided to keep the product as clean as possible, which is a perfect niche for flow maps. Since the thickness of arrows is determined by the data behind it (i.e., asylum seekers from Asia) the actual data values can be removed. Without them, it is still easy to determine that more refugees arrive from Asia than any other region, and it is even possible to rank these regions of origin: Asia, Africa, Europe, South America, and then the Caribbean.

When producing flow maps it can be challenging to portray an accurate arrow thickness when you also have to curve that arrow. This is because of the reduction of surface area on the inner edge of the curve, which creates a visual density. Therefore, you'll often have to manually adjust the arrow thickness away from the size dictated by the data.