Flow map
A flow map is a type of thematic map used in cartography to visualize the movement of objects between different locations. These objects can represent a variety of things, including people, goods, money, information, or even abstract concepts.
Key characteristics of flow maps:
- Arrows: The primary visual element of a flow map is the arrow. Arrows connect origin and destination locations, indicating the direction of movement.
- Line width: The width of the arrow is typically proportional to the quantity of the object being moved. Wider arrows represent larger flows, while narrower arrows represent smaller flows. This is a crucial element for conveying the magnitude of the movement.
- Location: Flow maps emphasize the origin and destination points of the movement, often represented as nodes or points on the map.
- Thematic: Flow maps are thematic maps because they focus on a specific theme (movement) rather than providing a general overview of the geography.
Uses and applications:
Flow maps are used across various disciplines, including:
- Geography: To illustrate migration patterns, trade routes, and transportation networks.
- Economics: To visualize the flow of goods, capital, and investments between regions or countries.
- Sociology: To depict the movement of populations or ideas.
- Transportation Planning: To analyze traffic patterns and optimize transportation infrastructure.
- Epidemiology: To track the spread of diseases.
Limitations:
- Overlapping Arrows: In areas with high volumes of movement, arrows can overlap and obscure the underlying geography, making the map difficult to read.
- Generalization: Flow maps often generalize the actual routes taken, representing movement as a straight line between origin and destination. This can be misleading if the actual paths are more complex.
- Complexity: When displaying numerous flows, flow maps can become visually cluttered and difficult to interpret. Careful design and simplification are necessary to create effective flow maps.
Alternatives:
Depending on the data and the specific objectives, other types of maps, such as choropleth maps or dot density maps, might be more appropriate for visualizing spatial data. A network graph is also an alternative but focuses more on connections than geographical representation.