Calculate Density
The Calculate Density tool creates a density map from point or line features by spreading known quantities of some phenomenon (represented as attributes of the points or lines) across the map. The result is a layer of areas classified from least dense to most dense.
For point input, each point should represent the location of some event or incident, and the result layer represents a count of the incident per unit area. A higher density value in a new location means that there are more points near that location. In many cases, the result layer can be interpreted as a risk surface for future events. For example, if the input points represent locations of lightning strikes, the result layer can be interpreted as a risk surface for future lightning strikes.
For line input, the line density surface represents the total amount of line that is near each location. The units of the calculated density values are the length of line per unit area. For example, if the lines represent rivers, the result layer will represent the total length of rivers that are within the search radius. This result can be used to identify areas that are hospitable to grazing animals.
Other use cases of this tool include the following:
- Creating crime density maps to help police departments properly allocate resources to high crime areas.
- Calculating densities of hospitals within a county. The result layer will show areas with high and low accessibility to hospitals, and this information can be used to decide where new hospitals should be built.
- Identifying areas that are at high risk of forest fires based on historical locations of forest fires.
- Locating communities that are far from major highways in order to plan where new roads should be constructed.
Choose input point or line layer from which to calculate density
The input point or line layer that will be used to calculate the density layer.
Use a count field
Provide a field specifying the number of incidents at each location. For example, if you have points that represent cities, you can use a field representing the population of the city as the count field, and the resulting population density layer will calculate larger population densities near cities with larger populations.
If the default choice of None is used, each location will be assumed to represent a single count.
Search distance
Enter a distance specifying how far to search to find point or line features when calculating density values. For example, if you provide a search distance of 10,000 meters, the density of any location in the output layer is calculated based on features that are within 10,000 meters of the location. Any location that does not have any incidents within 10,000 meters will receive a density value of zero.
If no distance is provided, a default will be calculated that is based on the locations of the input features and the values in the count field (if a count field is provided).
Output area units
Specify the output area unit. Density is count divided by area, and this parameter specifies the unit of the area in the density calculation.
Output cell size
Enter the cell size and unit for the output rasters.
Result layer name
This is the name of the layer that will be created in My Content and added to the map. The default name is based on the tool name and the input layer name. If the layer already exists, you will be asked to provide another name.
Using the Save result in drop-down box, you can specify the name of a folder in My Content where the result will be saved.