Heat map symbology draws point features as a representative surface of relative density. Use heat map symbology when many points are close together and cannot be easily distinguished. This approach displays the relative density of points using a color scheme, ideally one that is a smoothly varying set of colors ranging from cool (low density of points) to hot (high density of points). Heat map symbology can also represent the density of points weighted by an attribute. For example, point features representing apartment buildings can be weighted by the number of units so that larger buildings have a greater contribution to the calculation of density. Heat map symbology is calculated using the kernel density method.
Heat map symbology is a dynamic raster surface that changes as you zoom in and out. For example, if you map a city's crime hot spots, zooming out shows a bigger picture of criminal activity across the city, while zooming in shows more detailed density patterns in particular neighborhoods without having to reset symbology properties. You could also use time properties to create an animated raster surface and visualize both temporal and spatial change of a city's crime hot spots. To avoid dynamic changes to heat map symbology with scale without converting the layer to a raster output, set a reference scale on your map. Heat map symbology is only a visualization of your data. To perform analysis based on a density surface, you can convert your heat map symbology to a static raster output.
Since heat mapping provides a representation of point distribution, it works best with a large number of point features, especially if they overlap. Use another symbology method for sparse or small distributions of points.
- Select a feature layer in the Contents pane and click the Appearance tab.
- On the Appearance tab, in the Drawing group, click the Symbology drop-down menu.
- In the Symbology gallery, click Heat Map.The Symbology pane appears, displaying the current symbol information.
- On the Primary symbology tab , set the Radius to control the area searched when calculating the density of features. The radius is measure in points.
- Choose an attribute field with numeric data for Weight field to use weighted features.
- Choose a Color scheme.
- Optionally type new values for the Upper Label and Lower Label of the legend shown in the Contents pane and in a layout.
- Set the Rendering quality to Fastest to speed up the drawing time of your map or Best to maximize image quality.
Heat maps in 3D
You can draw point feature layers with heat map symbology only if they are in the 2D Layers category of a scene. You cannot move a layer drawn with heat map symbology into the 3D Layers category of a scene. By default, point layers drawn with heat map symbology in a scene will be displayed using real-world units. If you then draw the layer with different symbology, it will still be drawn in real-world units, which may result in symbols that draw too small to see. To change this, right-click on the layer in the Contents pane and click Properties. In the Layer Properties dialog box, click the Display tab and uncheck Display 3D symbols in real-world units.
Convert a heat map to a static raster
To identify raster values on your heat map or to use it for other analysis, a static raster output is more useful.
- In the Symbology pane click and click Convert to static raster.The Kernel Density tool opens in the Geoprocessing pane with parameters populated to match the settings of the heat map layer symbology.
- Run the tool.The raster output is added to the current map symbolized to match the heat map layer.