Summary
Calculates accumulated distance for each cell to sources, allowing for straight-line distance, cost distance, and true surface distance, as well as vertical and horizontal cost factors.
Usage
This raster analysis portal tool is available when you are signed in to an ArcGIS Enterprise
portal that has an ArcGIS Image Server configured for Raster Analysis . When the tool is invoked, ArcGIS Pro serves as a client and the processing occurs in the servers federated with ArcGIS Enterprise. The portal tool accepts layers from your portal as input and creates output in your portal.The input raster layer supports a layer from the portal, a URI or URL to an image service, or the output from the Make Image Server Layer tool. The input feature layer can be a layer from the portal or a URI or URL to a feature service. This tool does not support local raster data or layers. While you can use local feature data and layers as input to this portal tool, best practice is to use layers from your portal as input.
When the input source data is an image service, 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.
When the input source data is a feature service, the source locations are converted internally to a raster before performing the analysis. The resolution of the raster can be controlled with the Cell Size environment. By default, if no other rasters are specified in the tool, the resolution will be determined by the shorter of the width or height of the extent of the input feature in the input spatial reference, divided by 250.
To avoid this situation, as an intermediate step, you could 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 could select a small cell size to capture the appropriate amount of detail from the input features.
If there is NoData on any of these inputs: Input cost raster, Input surface raster, Input vertical raster, or Input horizontal raster, the cells at those locations across all inputs are ignored in the calculation. NoData on any of these rasters is persisted throughout the calculation and is therefore NoData on all outputs.
If a source falls on NoData in any of the corresponding input rasters, it is ignored in the analysis, and therefore no distance from that source will be calculated.
When no Extent environment setting is specified, the processing extent is determined in the following way:
If only the Input raster or feature source data and Input barrier raster or feature data are specified, the union of the inputs, expanded by two cell widths on each side, is used as the processing extent. The reason the output raster is expanded by two rows and columns is so that when the outputs are used in Optimal Path As Raster and Optimal Path As Line the generated paths can move around the barriers. To use the extent as an implicit barrier, you must explicitly set the Extent in the environment settings.
If any of the following raster datasets are specified: Input surface raster, Input cost raster, Input vertical raster, or Input horizontal raster, the processing extent is the intersection of these rasters.
When the Cell Size or Snap Raster environment settings are not specified, and there are multiple rasters specified as inputs, the Cell Size and Snap Raster are set based on an order of precedence: Input cost raster, Input surface raster, Input vertical raster, Input horizontal raster, Input raster or feature source data, and Input barrier raster or feature data.
The default values for the Vertical factor modifiers are the following:
Keyword Zero Low High Slope Power Cos Sec factor cut cut power power angle angle ------------------------ ------ ----- ----- ----- ----- ----- ----- Binary 1.0 -30 30 ~ ~ ~ ~ Linear 1.0 -90 90 1/90 ~ ~ ~ Symmetric linear 1.0 -90 90 1/90 ~ ~ ~ Inverse linear 1.0 -45 45 -1/45 ~ ~ ~ Symmetric inverse linear 1.0 -45 45 -1/45 ~ ~ ~ Cos ~ -90 90 ~ 1.0 ~ ~ Sec ~ -90 90 ~ 1.0 ~ ~ Cos_sec ~ -90 90 ~ ~ 1.0 1.0 Sec_cos ~ -90 90 ~ ~ 1.0 1.0The output of the Spatial Analyst Aspect tool can be used as input for the Input horizontal raster.
The default values for the Horizontal factor modifiers are the following:
Keywords Zero factor Cut angle Slope Side value -------------- ----------- ----------- ----- --------- Binary 1.0 45 ~ ~ Forward 0.5 45 (fixed) ~ 1.0 Linear 0.5 181 1/90 ~ Inverse linear 2.0 180 -1/90 ~
If any of the source characteristics parameters are specified using a field, the source characteristic will be applied on a source-by-source basis, according to the information in the given field for the source data. When a keyword or a constant value is given, it will be applied to all sources.
The characteristics of the source, or the movers from or to a source, can be controlled by specific parameters.
- Initial accumulation sets the initial cost before the movement begins.
- Maximum accumulation specifies how much cost a source can accumulate before reaching its limit.
- Multiplier to apply to costs specifies the mode of travel or magnitude at the source.
- Travel direction identifies whether the mover is starting at a source and moving to nonsource locations or starting at nonsource locations and moving back to a source.
If Initial accumulation is specified, the source locations on the output cost distance surface will be set to the Initial accumulation value; otherwise, the source locations on the output cost distance surface will be set to zero.
See Analysis environments and Spatial Analyst for additional details on the geoprocessing environments that apply to this tool.
Syntax
arcpy.ra.DistanceAccumulation(inputSourceRasterOrFeatures, outputDistanceAccumulationRasterName, {inputBarrierRasterOrFeatures}, {inputSurfaceRaster}, {inputCostRaster}, {inputVerticalRaster}, {verticalFactor}, {inputHorizontalRaster}, {horizontalFactor}, {outputBackDirectionRasterName}, {outputSourceDirectionRasterName}, {outputSourceLocationRasterName}, {sourceInitialAccumulation}, {sourceMaximumAccumulation}, {sourceCostMultiplier}, {sourceDirection}, {distanceMethod})| Parameter | Explanation | Data Type |
inputSourceRasterOrFeatures | The input source locations. This is an image service or feature service that identifies the cells or locations from which, or to which, the least accumulated cost distance for every output cell location is calculated. For an image service, the input type can be integer or floating point. | Raster Layer; Feature Layer |
outputDistanceAccumulationRasterName | The output distance accumulation raster name. The distance accumulation raster contains the accumulative distance for each cell from, or to, the least-cost source. | String |
inputBarrierRasterOrFeatures (Optional) | The dataset that defines the barriers. The barriers can be defined by an integer or a floating-point image service, or by a feature service. For an image service barrier, the barrier must have a valid value, including zero, and the areas that are not barriers must be NoData. | Raster Layer; Feature Layer |
inputSurfaceRaster (Optional) | An image service defining the elevation values at each cell location. The values are used to calculate the actual surface distance covered when passing between cells. | Image Service; Raster Layer |
inputCostRaster (Optional) | An image service defining the impedance or cost to move planimetrically through each cell. The value at each cell location represents the cost-per-unit distance for moving through the cell. Each cell location value is multiplied by the cell resolution while also compensating for diagonal movement to obtain the total cost of passing through the cell. The values of the cost raster can be integer or floating point, but they cannot be negative or zero (you cannot have a negative or zero cost). | Image Service; Raster Layer |
inputVerticalRaster (Optional) | An image service defining the z-values for each cell location. The values are used for calculating the slope used to identify the vertical factor incurred when moving from one cell to another. | Image Service; Raster Layer |
verticalFactor (Optional) | The Vertical factor object defines the relationship between the vertical cost factor and the vertical relative moving angle (VRMA). There are several factors with modifiers from which to select that identify a defined vertical factor graph. The graphs are used to identify the vertical factor used in calculating the total cost for moving into a neighboring cell. In the descriptions below, vertical factor (VF) defines the vertical difficulty encountered in moving from one cell to the next, and VRMA identifies the slope angle between the FROM or processing cell and the TO cell. The object comes in the following forms: VfBinary, VfLinear, VfInverseLinear, VfSymLinear, VfSymInverseLinear, VfCos, VfSec, VfSec, VfCosSec, and VfSecCos The definitions and parameters of these forms are as follows:
The modifiers to the vertical parameters are as follows:
| Vertical Factor |
inputHorizontalRaster (Optional) | A raster defining the horizontal direction at each cell. The values on the raster must be integers ranging from 0 to 360, with 0 degrees being north, or toward the top of the screen, and increasing clockwise. Flat areas should be given a value of -1. The values at each location will be used in conjunction with the horizontal_factor parameter to determine the horizontal cost incurred when moving from a cell to its neighbors. | Image Service; Raster Layer |
horizontalFactor (Optional) | The Horizontal Factor object defines the relationship between the horizontal cost factor and the horizontal relative moving angle. There are several factors with modifiers from which to select that identify a defined horizontal factor graph. The graphs are used to identify the horizontal factor used in calculating the total cost of moving into a neighboring cell. In the descriptions below, horizontal factor (HF) defines the horizontal difficulty encountered when moving from one cell to the next, and horizontal relative moving angle (HRMA) identifies the angle between the horizontal direction from a cell and the moving direction. The object comes in the following forms: HfBinary, HfForward, HfLinear, and HfInverseLinear The definitions and parameters of these are as follows:
The modifiers to the horizontal keywords are as follows:
| Horizontal Factor |
outputBackDirectionRasterName (Optional) | The output back direction raster name. The back direction raster contains calculated directions in degrees. The direction identifies the next cell along the optimal path back to the least accumulative cost source while avoiding barriers. The range of values is from 0 degrees to 360 degrees. The value 0 is reserved for the source cells. Due east (right) is 90 degrees, and the values increase clockwise (180 is south, 270 is west, and 360 is north). The output raster is of type float. | String |
outputSourceDirectionRasterName (Optional) | The output source direction raster name. The source direction raster identifies the direction of the least accumulated cost source cell as an azimuth in degrees. The range of values is from 0 degrees to 360 degrees. The value 0 is reserved for the source cells. Due east (right) is 90 degrees, and the values increase clockwise (180 is south, 270 is west, and 360 is north). The output raster is of type float. | String |
outputSourceLocationRasterName (Optional) | The source location raster is a multiband output. The first band contains a row index, and the second band contains a column index. These indexes identify the location of the source cell that is the least accumulated cost distance away. | String |
sourceInitialAccumulation (Optional) | The initial accumulative cost to begin the cost calculation. Allows for the specification of the fixed cost associated with a source. Instead of starting at a cost of zero, the cost algorithm will begin with the value set by source_initial_accumulation. The values must be zero or greater. The default is 0. | Double; Field |
sourceMaximumAccumulation (Optional) | The maximum accumulation for the traveler for a source. The cost calculations continue for each source until the specified accumulation is reached. The values must be greater than zero. The default accumulation is to the edge of the output raster. | Double; Field |
sourceCostMultiplier (Optional) | The multiplier to apply to the cost values. This allows for control of the mode of travel or the magnitude at a source. The greater the multiplier, the greater the cost to move through each cell. The values must be greater than zero. The default is 1. | Double; Field |
sourceDirection (Optional) | Specifies the direction of the traveler when applying horizontal and vertical factors.
Specify the FROM_SOURCE or TO_SOURCE keyword, which will be applied to all sources, or specify a field in the source data that contains the keywords to identify the direction of travel for each source. That field must contain the string FROM_SOURCE or TO_SOURCE. | String; Field |
distanceMethod (Optional) | Specifies whether to calculate the distance using a planar (flat earth) or a geodesic (ellipsoid) method.
| String |
Derived Output
| Name | Explanation | Data Type |
| outputDistanceAccumulationRaster | The output distance accumulation raster. | Raster |
| outputBackDirectionRaster | The output back direction raster. | Raster |
| outputSourceDirectionRaster | The output source direction raster. | Raster |
| outputSourceLocationRaster | The output source location raster. | Raster |
Code sample
The following Python Window script demonstrates how to use the DistanceAccumulation tool.
import arcpy
arcpy.DistanceAccumulation_ra('https://MyPortal.esri.com/server/rest/services/Hosted/sources/ImageServer',
'OutAccumulationRaster',
'https://MyPortal.esri.com/server/rest/services/Hosted/barrier/ImageServer',
'https://MyPortal.esri.com/server/rest/services/Hosted/surface/ImageServer',
'https://MyPortal.esri.com/server/rest/services/Hosted/cost/ImageServer')Calculate, for each cell, the least accumulative cost distance to the nearest source, while accounting for surface distance and horizontal and vertical cost factors.
# Name: DistanceAccumulation_Ex_02.py
# Description: Calculates the distance accumulation.
# Requirements: ArcGIS Image Server
# Import system modules
import arcpy
# Set local variables
inputSourceRasterOrFeatures = 'https://MyPortal.esri.com/server/rest/services/Hosted/sources/ImageServer'
outputDistanceAccunulationName = "outDistAccum"
inputBarrierRasterOrFeatures = 'https://MyPortal.esri.com/server/rest/services/Hosted/barrier/ImageServer'
inputSurfaceRaster = 'https://MyPortal.esri.com/server/rest/services/Hosted/surface/ImageServer'
inputCostRaster = 'https://MyPortal.esri.com/server/rest/services/Hosted/cost/ImageServer'
inputVerticalRaster = 'https://MyPortal.esri.com/server/rest/services/vertical/sources/ImageServer'
verticalFactor = ""
inputHorizontalRaster = 'https://MyPortal.esri.com/server/rest/services/Hosted/horizontal/ImageServer'
horizontalFactor = ""
outputBackDirectionRasterName = "outBackDir"
outputSourceDirectionRasterName = "outSourceDir"
outputSourceLocationRasterName = "outSourceLocation"
sourceInitialAccumulation = "IntitalAccum"
sourceMaximumAccumulation = "500000"
sourceCostMultiplier = "CostMultiplier"
sourceDirection = "FROM_SOURCE"
distanceMethod = "PLANAR"
# Execute
arcpy.DistanceAccumulation_ra(inputSourceRasterOrFeatures, outputDistanceAccumulationName,
inputBarrierRasterOrFeatures, inputSurfaceRaster,
inputCostRaster, inputVerticalRaster, verticalFactor,
inputHorizontalRaster, horizontalFactor,
outputBackDirectionRasterName, outputSourceDirectionRasterName,
outputSourceLocationRasterName, sourceInitialAccumulation,
sourceMaximumAccumulation,sourceCostMultiplier, sourceDirection, distanceMethod)Environments
Licensing information
- Basic: Requires ArcGIS Image Server
- Standard: Requires ArcGIS Image Server
- Advanced: Requires ArcGIS Image Server