ETG_CostAllocationSource

Cost Allocation - Costs from Source

Derives the catchment areas of the input features (Sources) using their spatial location and the weight of each source. The function allocates the cells of the output raster to the sources based on minimum cost to reach a source from the cell. The cost is calculated as distance from the cell to the source multiplied by the weight of the source. The smaller the weight value of a source is, the greater the influence of the source is.

This function produces results similar to the results from the Weighted Voronoi Diagram function. The algorithm is different and non-integer weights can be used. Since the Weighted Voronoi Diagram is much faster, the better option is to use it instead of this function unless you need to have double values for the weights.

The performance of the function depends very much on the difference between the smallest and largest weights. The larger this difference is, the slower the function will be.

Inputs:

Input point feature dataset - Sources
Output raster name and format
The cell size of the output raster.
Source ID field. The values from this field will be allocated to the cells of the output raster.
Weight field. Any numeric field (integer or double) can be used as a weight field.
Cutoff cost - cells with larger than this cost (distance x weight) to reach will not be allocated to any source.

Outputs:

An integer raster. Each cell will have as a value the ID of the closest input point (Source). The extent of the output is equal to the extent of the input feature class.

Example:

Points labeled with their weights. Integer weights used - the results very similar to the results produced by Weighted Voronoi Diagram In this case the use of Weighted Voronoi Diagram function is recommended.

Points labeled with their weights. Double values for the weights used. The difference between the smallest weights (indicated on the image) and the largest ones close to 100 times.

Expect long processing time.

Notes:

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 - 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	CostAllocationSource
<InputFeatures>	A String - the full path to the input feature dataset.
<output raster>	A String - the full name of the output raster.
<CellSize>	A Double representing the cell size of the output raster.
<IDField>	A String representing the name of the field in the input point feature class to be used as point ID.
<WeightField>	A String representing the name of the field in the input point feature class that are going to be used as weights.
<CutOff>	A Double representing the cut off cost - the value of the cells with larger than this cost (distance x weight) to reach will be set to NODATA.

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")

CellSize

Language	Syntax
Python	subprocess.call([ETSPath, "CostAllocationSource", "InputFeatures", "output raster", "CellSize", "IDField", "WeightField", "CutOff"])
.NET using ETSRun.exe	StartInfo.FileName = ETSPath StartInfo.Arguments = "CostAllocationSource" "InputFeatures" "output raster" "CellSize" "IDField" "WeightField" "CutOff"
.NET using ETSOutX.dll	CostAllocationSource(InputFeatures, output raster, CellSize, IDField, WeightField, CutOff)
ArcPy	arcpy.CostAllocationSource("InputFeatures", "output raster", "CellSize", "IDField", "WeightField", "CutOff")

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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