ETG_Density

Kernel Density

Uses Kernel Density Estimation to interpolate a surface from the input Point or Polyline features. The function fits a symmetrical surface over each input point using Gaussian kernel.

The surface has maximum value in the input point, decreases as the distance from the input point increases and has 0 values at distance equal to the search radius.
The volume of the created surface is equal to the value of the input point.
The density of each cell of the output raster is calculated by adding the values of all individual surfaces for that cell.

The search radius does not influence the volume of the surface, but has a major impact on the generalization of the data. The larger the search tolerance, the smoother and more generalized surface will be interpolated. As you can see from the image below the selection of the search radius is very important and influences greatly the surface. You should evaluate your data and have always in mind what is the goal of the task when deciding on what search tolerance to use.

Inputs:

Input point or polyline feature dataset.
Output raster name and format.
Cell Size of the output raster.
Value field - a field from the attribute table to be used as a source for the values of the raster. If the input is of PointZ or PolylineZ type, the Z values of the features can be used as source for the raster values.
Interpolation radius.
Output Area Units (optional) - The value of each cell of the output raster will actually have value measured in Value per square unit. The default unit is the unit of the spatial reference of the input dataset, but you might want to change this to a different area unit (for example incidents per square kilometer).

Outputs:

A floating point raster.

Examples - the surface created from the 6 points in the profile above:

Output raster - Interpolation Radius = 2000 meters - smoother more generalized appearance.

Output raster - Interpolation Radius = 1000 meters - more pronounced influence of the individual points.

Both surfaces superimposed - two very different surfaces. The volume of both however is the same and is equal to the sum of the values of the input points.

Notes:

When the value in the Value field is NULL, it is interpreted as 0 for Density calculations.
The input format accepted are file based rasters - ERDAS IMAGINE or Tagged Image File Format (TIFF).
The .NET ToolBox for ArcGIS Desktop accepts also FileGDB Raster inputs.
For file based rasters initially the name of the output raster define the raster format:
- .img extension (for example raster1.img) - ERDAS IMAGINE image.
- .tif extension (for example raster1.tif) - TIFF image.
- The initial output raster format can be changed by selecting the desired output in the dialog.

Running Programmatically

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Parameters

Expression	Explanation
Function Name	DensityRaster
<input dataset>	A String representing the input layer. Must be of Point or Polyline type.
<output raster>	A String - the full name of the output raster.
<cell size>	A Double representing the cell size of the output raster.
<value field>	A String representing the name of the field which values are going to be used for interpolation.
<interpolate radius>	A Number - see main description above.
{output units}	A String - possible values are "SquareMeters", "SquareKilometers", "Hectares", "SquareFeet", "SquareMiles", "Acres", "SquareYards", "Decares", "Ares".

Running the function

ETSPath used in the table below is the full path to ETSRun.exe (E.G. "C:\Program Files\ETSpatial Techniques\ETSurface\ETSRun.exe")

Language	Syntax
Python	subprocess.call([ETSPath, "DensityRaster", "input dataset", "output raster", "cell size", "value field", "interpolate radius", "output units"])
.NET using ETSRun.exe	StartInfo.FileName = ETSPath StartInfo.Arguments = "DensityRaster" "input dataset" "output raster" "cell size" "value field" "interpolate radius" "output units"
.NET using ETSOutX.dll	DensityRaster(input dataset, output raster, cell size, value field, interpolate radius, output units)
ArcPy	arcpy.DensityRaster("input dataset", "output raster", "cell size", "value field", "interpolate radius", "output units")

Notes:

<> - required parameter
{} - optional parameter
See examples for Python , .NET or ArcPy
The argument separator for StartInfo.Arguments is space. If a string might contain a space, you need to double quote it.

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