# Euclidean Allocation

## Summary

Calculates, for each cell, the nearest source based on Euclidean distance.

## Usage

• The input source data can be a feature class or raster.

• When the input source data is a raster, the set of source cells consists of all cells in the source raster that have valid values. Cells that have NoData values are not included in the source set. The value 0 is considered a legitimate source. A source raster can be easily created using the extraction tools.

• When the input source data is a feature class, the source locations are converted to a raster internally before performing the analysis.

• When using polygon feature data for the input source data, care must be taken with how the output cell size is handled when it is coarse, relative to the detail present in the input. The internal rasterization process employs the same default Cell assignment type as the Polygon to Raster tool, which is the cell center method. This means that data not located at the center of the cell will not be included in the intermediate rasterized source output, so it will not be represented in the distance calculations. For example, if your sources are a series of small polygons (such as building footprints) that are small relative to the output cell size, it is possible that only a few will fall under the centers of the output raster cells, seemingly causing most of the others to be lost in the analysis.

To avoid this situation, as an intermediate step, you could rasterize the input features directly with the Polygon to Raster tool and set a Priority field. Then use the resulting output as input to the particular distance tool you want to use. Alternatively, you could select a small cell size to capture the appropriate amount of detail from the input features.

• The Maximum distance is specified in the same map units as the input source data.

• The input value raster is useful if the input raster or feature source data is a raster derived from a function that results in either one or zero. These functions lose their original zone values associated with the source cell locations. The input value raster can either restore these values or allow analysis on additional combinations of zone values within the source cells.

• If an input value raster is used, it may change the configuration and results of the Euclidean allocation output. It will not affect the optional Euclidean distance or direction results.

• The Output cell size can be defined by a numeric value or obtained from an existing raster dataset. If the cell size hasn’t been explicitly specified as the parameter value, it is derived from the Cell Size environment if it has been specified. If the parameter cell size or the environment cell size have not been specified, the default output cell size is determined based on the type of input dataset as follows:

• If the input dataset is a raster, the cell size of the dataset is used.
• If the input dataset is a feature and the Snap Raster environment has been set, the cell size of the snap raster is used. If no snap raster is set, the cell size is calculated from the shorter of the width or height of the extent divided by 250, where the extent is in the Output Coordinate System specified in the environment.
• If the cell size is specified using a numeric value, the tool will use it directly for the output raster.

If the cell size is specified using a raster dataset, the parameter will show the path of the raster dataset instead of the cell size value. The cell size of that raster dataset will be used directly in the analysis, provided the spatial reference of the dataset is the same as the output spatial reference. If the spatial reference of the dataset is different than the output spatial reference, it will be projected based on the selected Cell Size Projection Method.

• This tool creates internal scratch files during processing. You can control this location using the system temp variable (TEMP, TMP, User Profile). If the geoprocessing tool is unable to write to this location, an error will be generated. While processing large data there can be a very large file created so make sure a lot of disk space is available. This internal scratch file is managed by the application and gets deleted when the application is closed.

• See Analysis environments and Spatial Analyst for additional details on the geoprocessing environments that apply to this tool.

## Syntax

`EucAllocation (in_source_data, {maximum_distance}, {in_value_raster}, {cell_size}, {source_field}, {out_distance_raster}, {out_direction_raster}, {distance_method})`
 Parameter Explanation Data Type in_source_data The input source locations.This is a raster or feature dataset that identifies the cells or locations to which the Euclidean distance for every output cell location is calculated.For rasters, the input type can be integer or floating point. If the input source raster is floating point, the {in_value_raster} must be set, and it must be of integer type. The value raster will take precedence over any setting of the {source_field}. Raster Layer; Feature Layer maximum_distance(Optional) Defines the threshold that the accumulative distance values cannot exceed.If an accumulative Euclidean distance value exceeds this value, the output value for the cell location will be NoData.The default distance is to the edge of the output raster. Double in_value_raster(Optional) The input integer raster that identifies the zone values that should be used for each input source location.For each source location (cell or feature), the value defined by the {in_value_raster} will be assigned to all cells allocated to the source location for the computation. The value raster will take precedence over any setting for the {source_field}. Raster Layer cell_size(Optional) The cell size of the output raster that will be created.This parameter can be defined by a numeric value or obtained from an existing raster dataset. If the cell size hasn't been explicitly specified as the parameter value, the environment cell size value will be used if specified; otherwise, additional rules will be used to calculate it from the other inputs. See the usage for more detail. Analysis Cell Size source_field(Optional) The field used to assign values to the source locations. It must be of integer type.If the {in_value_raster} has been set, the values in that input will have precedence over any setting for the {source_field}. Field out_distance_raster(Optional) The output Euclidean distance raster.The distance raster identifies, for each cell, the Euclidean distance to the closest source cell, set of source cells, or source location.The output raster is of floating-point type. Raster Dataset out_direction_raster(Optional) The output Euclidean direction raster.The direction raster contains the calculated direction, in degrees, that each cell center is from the closest source cell center.The range of values is from 0 degrees to 360 degrees, with 0 reserved for the source cells. Due east (right) is 90 and the values increase clockwise (180 is south, 270 is west, and 360 is north).The output raster is of integer type. Raster Dataset distance_method(Optional) Determines whether to calculate the distance using a planar (flat earth) or a geodesic (ellipsoid) method.PLANAR —The calculation will be performed on a projected flat plane using a 2D Cartesian coordinate system. This is the default method.GEODESIC —Distances are calculated on the ellipsoid. Therefore, regardless of input or output projection, the results do not change. String

#### Return Value

 Name Explanation Data Type out_allocation_raster The output Euclidean allocation raster.The cell values (zones) identify the nearest source location.The output raster is of integer type. Raster

## Code sample

EucAllocation example 1 (Python window)

The following Python Window script demonstrates how to use the EuclideanAllocation tool.

``````import arcpy
from arcpy import env
from arcpy.sa import *
env.workspace = "C:/sapyexamples/data"
eucAllocate = EucAllocation("observers", 50000, "elevation", 25, "FID",
"c:/sapyexamples/output/outeucdist",
"c:/sapyexamples/output/outeucdir")
eucAllocate.save("c:/sapyexamples/output/eucalloc")``````
EucAllocation example 2 (stand-alone script)

Calculates, for each cell, the zone of the closest source location in Euclidean distance.

``````# Name: EucAllocation_Ex_02.py
# Description: Calculates, for each cell, the zone of the closest
#              source location in Euclidean distance.
# 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
inSource = "observers.shp"
maxDist = 50000
valRaster = "elevation"
cellSize = 25
sourceField = "FID"
optOutDist = "c:/sapyexamples/output/outeucdist02"
optOutDir = "c:/sapyexamples/output/outeucdir02"

# Execute EucAllocation
eucAllocate = EucAllocation(inSource, maxDist, valRaster, cellSize,
sourceField, optOutDist, optOutDir)

# Save the output
eucAllocate.save("c:/sapyexamples/output/eucalloc02")``````

## Licensing information

• Basic: Requires Spatial Analyst
• Standard: Requires Spatial Analyst