Point Density (Spatial Analyst)
Summary
Calculates a magnitude per unit area from point features that fall within a neighborhood around each cell.
Illustration
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OutRas = PointDensity(InPts, None, 30) |
Usage
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Larger values of the radius parameter produce a more generalized density raster. Smaller values produce a raster that shows more detail.
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Only the points that fall within the neighborhood are considered when calculating the density. If no points fall within the neighborhood at a particular cell, that cell is assigned NoData.
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If the area unit scale factor units are small, relative to the distance between the points, the output raster values may be small. To obtain larger values, use the area unit scale factor for larger units (for example, square kilometers versus square meters).
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The values on the output raster will always be floating point.
Syntax
| Parameter | Explanation | Data Type |
in_point_features |
The input point features for which to calculate the density. | Feature Layer |
population_field |
Field denoting population values for each point. The population field is the count or quantity to be used in the calculation of a continuous surface. Values in the population field may be integer or floating point. The options and default behaviours for the field are listed below.
| Field |
cell_size (Optional) | The cell size for the output raster dataset. This is the value in the environment if specifically set. If the environment is not set, then cell size is the shorter of the width or height of the output extent in the output spatial reference, divided by 250. | Analysis Cell Size |
neighborhood (Optional) |
Dictates the shape of the area around each cell used to calculate the density value. This is a Neighborhood class. There are four types of neighbourhood class: NbrAnnulus, NbrCircle, NbrRectangle, and NbrWedge. The forms and descriptions of the classes are:
The default is NbrCircle, where radius is the shortest of the width or height of the output extent in the output spatial reference, divided by 30. | Neighborhood |
area_unit_scale_factor (Optional) |
The desired area units of the output density values. A default unit is selected based on the linear unit of the projection of the output spatial reference. You can change this to the appropriate unit if you wish to convert the density output. Values for line density convert the units of both length and area. For example, if your input units are meters the default output area density units will be square kilometers for point features or kilometers per square kilometer for polyline features. The default density units based on the input feature units are:
| String |
Return Value
| Name | Explanation | Data Type |
| out_raster |
The output point density raster. It is always a floating point raster. | Raster |
Code Sample
This example calculates a density raster from a point shape file.
import arcpy
from arcpy import env
from arcpy.sa import *
env.workspace = "C:/sapyexamples/data"
pdensOut = PointDensity("rec_sites.shp", "NONE", 60, NbrCircle(2500, "MAP"))
pdensOut.save("C:/sapyexamples/output/pointdensity")
This example calculates a density raster from a point shape file.
# Name: PointDensity_Ex_02.py
# Description: Calculates a magnitude per unit area from point
# features that fall within a neighborhood around each cell.
# Requirements: Spatial Analyst Extension
# Import system modules
import arcpy
from arcpy import env
from arcpy.sa import *
# Set environment settings
env.workspace = "C:/sapyexamples/data"
# Set local variables
inFeatures = "rec_sites.shp"
populationField = "NONE"
cellSize = 60
# Create the Neighborhood Object
radius = 2500
myNbrCirc = NbrCircle(radius, "MAP")
# Check out the ArcGIS Spatial Analyst extension license
arcpy.CheckOutExtension("Spatial")
# Execute PointDensity
outPdens = PointDensity(inFeatures, populationField, cellSize,
myNbrCirc, "SQUARE_KILOMETERS")
# Save the output
outPdens.save("C:/sapyexamples/output/outpdens")