A density map, sometimes called a heatmap, shows where observations cluster by varying visual intensity. Darker, more saturated marks indicate higher concentrations; lighter marks recede. section 6.3.1
Use density maps when:
- Points form visible clumps, such as rat sightings, population, or harmful algal blooms. section 6.3.1
- You need to emphasize broad areas of concentration rather than preserve every fine geographic detail. section 6.3.1
- You choose a palette that remains understandable in black and white, not merely attractive in color. section 6.3.1
Harmful algal blooms in California
A density map of harmful freshwater algal blooms observed from 2015 to 2021 uses darker, more saturated orange for high-concentration areas, making a few hotspots stand out.
