Calculate Density (Standard Feature Analysis)

Summary

Creates a density map from point or line features by spreading known quantities of a 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.

Illustration

Usage

• For point input, each point should represent the location of an event or incident, and the result layer will represent 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:

  • Create crime density maps to help police departments properly allocate resources to high crime areas.
  • Calculate 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.
  • Identify areas that are at high risk of forest fires based on historical locations of forest fires.
  • Locate communities that are far from major highways to plan where new roads should be constructed.

Parameters

Dialog

Label	Explanation	Data Type
Input Features	The point or line features that will be used to calculate density.	Feature Set
Output Name	The name of the output layer that will be created on your portal.	String
Count Field (Optional)	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 no value is provided, each location will be assumed to represent a single count.	Field
Cell Size (Optional)	The cell size that will be used to create a mesh of points where density values are calculated. The smaller the value, the smoother the polygon boundaries will be. Conversely, with larger values, the polygon boundaries will be more coarse and jagged.	Double
Cell Size Units (Optional)	Specifies the units that will be used for the cell size value. A value is required if the cell size has been set. Miles—The units will be miles. Feet—The units will be feet. Kilometers—The units will be kilometers. Meters—The units will be meters.	String
Radius (Optional)	The distance that will be searched to find point or line features when calculating density values. For example, if you provide a radius of 1,800 meters, the density of any location in the output layer is calculated based on features that are within 1,800 meters of the location. Any location that does not have any incidents within 1,800 meters will receive a density value of zero. If no value is provided, a default will be calculated based on the locations of the input features and the values in the count field (if a count field is provided).	Double
Radius Units (Optional)	Specifies the units that will be used for the radius value. A value is required if the radius has been set. Miles—The units will be miles. Feet—The units will be feet. Kilometers—The units will be kilometers. Meters—The units will be meters.	String
Bounding Polygons (Optional)	The layer containing the polygons where densities will be calculated. For example, if you are interpolating densities of fish in a lake, you can use the boundary of the lake in this parameter, and the output will only draw within the boundary of the lake.	Feature Set
Area Units (Optional)	Specifies the units that will be used for the calculated density values. Square miles—The units will be square miles. Square kilometers—The units will be square kilometers.	String
Classification Type (Optional)	Specifies how density values will be classified into polygons. Equal interval— Polygons will be created so that the range of density values is equal for each area. Geometric interval— Polygons will be created based on class intervals that have a geometric series. This ensures that each class range has approximately the same number of values in each class and that the change between intervals is consistent. Natural breaks— Class intervals for polygons will be created based on natural groupings of the data. Class break values are identified by best group similar values that maximize the differences between classes. Equal area— Polygons will be created so that the size of each area is equal. For example, if the result has more high-density values than low-density values, more polygons will be created for high densities. Standard deviation— Polygons will be created based on the standard deviation of the predicted density values.	String
Number of Classes (Optional)	The range of predicted values that will be divided into distinct classes. The range of values in each class is determined by the classification type. Each class defines the boundaries of the result polygons. The default is 10 and the maximum is 32.	Long

Derived Output

Label	Explanation	Data Type
Output Layer	The output polygon layer with classified density values.	Feature Set

Python

arcpy.sfa.CalculateDensity(inputLayer, outputName, {field}, {cellSize}, {cellSizeUnits}, {radius}, {radiusUnits}, {boundingPolygonLayer}, {areaUnits}, {classificationType}, {numClasses})

Name	Explanation	Data Type
inputLayer	The point or line features that will be used to calculate density.	Feature Set
outputName	The name of the output layer that will be created on your portal.	String
field (Optional)	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 no value is provided, each location will be assumed to represent a single count.	Field
cellSize (Optional)	The cell size that will be used to create a mesh of points where density values are calculated. The smaller the value, the smoother the polygon boundaries will be. Conversely, with larger values, the polygon boundaries will be more coarse and jagged.	Double
cellSizeUnits (Optional)	Specifies the units that will be used for the cell size value. A value is required if the cell size has been set. MILES—The units will be miles. FEET—The units will be feet. KILOMETERS—The units will be kilometers. METERS—The units will be meters.	String
radius (Optional)	The distance that will be searched to find point or line features when calculating density values. For example, if you provide a radius of 1,800 meters, the density of any location in the output layer is calculated based on features that are within 1,800 meters of the location. Any location that does not have any incidents within 1,800 meters will receive a density value of zero. If no value is provided, a default will be calculated based on the locations of the input features and the values in the count field (if a count field is provided).	Double
radiusUnits (Optional)	Specifies the units that will be used for the radius value. A value is required if the radius has been set. MILES—The units will be miles. FEET—The units will be feet. KILOMETERS—The units will be kilometers. METERS—The units will be meters.	String
boundingPolygonLayer (Optional)	The layer containing the polygons where densities will be calculated. For example, if you are interpolating densities of fish in a lake, you can use the boundary of the lake in this parameter, and the output will only draw within the boundary of the lake.	Feature Set
areaUnits (Optional)	Specifies the units that will be used for the calculated density values. SQUAREMILES—The units will be square miles. SQUAREKILOMETERS—The units will be square kilometers.	String
classificationType (Optional)	Specifies how density values will be classified into polygons. EQUALINTERVAL— Polygons will be created so that the range of density values is equal for each area. GEOMETRICINTERVAL— Polygons will be created based on class intervals that have a geometric series. This ensures that each class range has approximately the same number of values in each class and that the change between intervals is consistent. NATURALBREAKS— Class intervals for polygons will be created based on natural groupings of the data. Class break values are identified by best group similar values that maximize the differences between classes. EQUALAREA— Polygons will be created so that the size of each area is equal. For example, if the result has more high-density values than low-density values, more polygons will be created for high densities. STANDARDDEVIATION— Polygons will be created based on the standard deviation of the predicted density values.	String
numClasses (Optional)	The range of predicted values that will be divided into distinct classes. The range of values in each class is determined by the classification type. Each class defines the boundaries of the result polygons. The default is 10 and the maximum is 32.	Long

Derived Output

Name	Explanation	Data Type
outputLayer	The output polygon layer with classified density values.	Feature Set

Environments

Extent

Licensing information

• Basic: Requires your account in ArcGIS Enterprise to have the Perform Analysis privilege
• Standard: Requires your account in ArcGIS Enterprise to have the Perform Analysis privilege
• Advanced: Requires your account in ArcGIS Enterprise to have the Perform Analysis privilege