Euclidean Back Direction (Spatial Analyst)

Available with Spatial Analyst license.

Summary

Calculates, for each cell, the direction, in degrees, to the neighboring cell along the shortest path back to the closest source while avoiding barriers.

Tip:

The Distance Accumulation tool provides enhanced functionality or performance.

Learn more about Euclidean distance analysis

Usage

• The input source data can be a feature class or a raster. The feature class can be point, line or polygon.

• The output values are based on compass directions (90 to the east, 180 to the south, 270 to the west, and 360 to the north), with 0 reserved for the source cells.

• 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 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 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 uses the same default Cell assignment type value as the Feature to Raster tool, which is the cell center method. This means that data that is 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 can rasterize the input features directly with the Feature to Raster tool and set the Field parameter. Then use the resulting output as input to the particular distance tool you want to use. Alternatively, you can select a small cell size to capture the appropriate amount of detail from the input features.

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

• 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, in which 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.

• The default processing extent for this tool is the Union of Inputs value. The combined extent of both input datasets will be processed.

• This tool supports parallel processing. If your computer has multiple processors or processors with multiple cores, better performance may be achieved, particularly on larger datasets. See the Parallel processing with Spatial Analyst help topic for details on this capability and how to configure it.

  When using parallel processing, temporary data will be written to manage the data chunks being processed. The default temp folder location will be on your local C: drive. You can control the location of this folder by setting up a system environment variable named TempFolders and specifying the path to a folder to use (for example, E:\RasterCache). If you have admin privileges on your machine, you can also use a registry key (for example, [HKEY_CURRENT_USER\SOFTWARE\ESRI\ArcGISPro\Raster]).

  By default, this tool will use 50 percent of the available cores. If the input data is smaller than 5,000 by 5,000 cells in size, fewer cores may be used. You can control the number of cores the tool uses with the Parallel processing factor environment.

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

Parameters

Dialog

Label	Explanation	Data Type
Input raster or feature source data	The input source locations. This is a raster or feature dataset that identifies the cells or locations to which the Euclidean back direction for every output cell location is calculated. For rasters, the input type can be integer or floating point.	Raster Layer; Feature Layer
Input raster or feature barrier data (Optional)	The dataset that defines the barriers. The barriers can be defined by an integer or a floating-point raster, or by a point, line, or polygon feature.	Raster Layer; Feature Layer
Maximum distance (Optional)	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
Output 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 section for more detail.	Analysis Cell Size
Distance Method (Optional)	Specifies whether the distance will be calculated using a planar (flat earth) or a geodesic (ellipsoid) method. Planar—The distance calculation will be performed on a projected flat plane using a 2D Cartesian coordinate system. This is the default. Geodesic—The distance calculation will be performed on the ellipsoid. Regardless of input or output projection, the results will not change.	String

Return Value

Label	Explanation	Data Type
Output back direction raster	The output Euclidean back direction raster. The back direction raster contains the calculated direction in degrees. The direction identifies the next cell along the shortest path back to the closest source while avoiding barriers. 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 type float.	Raster

Python

EucBackDirection(in_source_data, {in_barrier_data}, {maximum_distance}, {cell_size}, {distance_method})

Name	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 back direction for every output cell location is calculated. For rasters, the input type can be integer or floating point.	Raster Layer; Feature Layer
in_barrier_data (Optional)	The dataset that defines the barriers. The barriers can be defined by an integer or a floating-point raster, or by a point, line, or polygon feature.	Raster Layer; Feature Layer
maximum_distance (Optional)	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
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 section for more detail.	Analysis Cell Size
distance_method (Optional)	Specifies whether the distance will be calculated using a planar (flat earth) or a geodesic (ellipsoid) method. PLANAR—The distance calculation will be performed on a projected flat plane using a 2D Cartesian coordinate system. This is the default. GEODESIC—The distance calculation will be performed on the ellipsoid. Regardless of input or output projection, the results will not change.	String

Return Value

Name	Explanation	Data Type
out_back_direction_raster	The output Euclidean back direction raster. The back direction raster contains the calculated direction in degrees. The direction identifies the next cell along the shortest path back to the closest source while avoiding barriers. 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 type float.	Raster

Code sample

EucDirection example 1 (Python window)

The following Python window script demonstrates how to use the EuclideanBackDirection tool.

import arcpy
from arcpy import env
from arcpy.sa import *
env.workspace = "C:/sapyexamples/data"
outEucBackDir = EucBackDirection("observers", "in_barriers", 35000, 50, 
                            "GEODESIC")
outEucBackDir.save("c:/sapyexamples/output/eucoutbackdir.tif")

EucDirection example 2 (stand-alone script)

Calculates the direction in degrees that each cell center is from the cell center of the closest source.

# Name: EucBackDirection_Ex_02.py
# Description: Calculates, for each cell, the direction,
#              in degrees, to the neighboring cell along
#              the shortest path back to the closest
#              source while avoiding barriers.
# 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"
inBarriers = "rivers.tif"
maxDist = 35000
cellSize = 50
distMethod = "GEODESIC"

# Check out the ArcGIS Spatial Analyst extension license
arcpy.CheckOutExtension("Spatial")

# Execute EucDirections
outEucBackDir = EucBackDirection(inSource, inBarriers, maxDist,
                            cellSize, distMethod)

# Save the output 
outEucBackDir.save("c:/sapyexamples/output/eucoutbackdir02.tif")

Environments

Auto Commit, Cell Size, Cell Size Projection Method, Compression, Current Workspace, Extent, Geographic Transformations, Mask, Output CONFIG Keyword, Output Coordinate System, Parallel Processing Factor, Scratch Workspace, Snap Raster, Tile Size

Licensing information

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