v3_Utilitiy Create Walkability Cost Raster

Create Walkability Cost Raster

Available with Spatial Analyst license.

Summary

Insert Text

Usage

This tool processes all polygons in the Reporting unit feature regardless of selections set. The ability to limit calculations to only selected reporting unit polygons is not supported in this release.
NOTE: For the most accurate results and shortest processing times, it is highly recommended that all input layers be in the same spatial reference.
NOTE: Enabling the Parallel Processing Factor environment can improve computation time for several ATtILA tools, but we have detected, on rare occasions, doing so can lead to spurious results. As a precaution, ATtILA will disable the Parallel Processing Factor environment for this tool. We hope to return this choice to the user once the impact on operational speed and accuracy of swapping geoprocessing tools with their pairwise counterparts has been assessed.
The Reporting unit feature is a zone dataset.
- A zone is defined as all areas in the input that have the same value. The areas do not have to be contiguous. The term "value" in this definition refers to the unique values in the Reporting unit ID field. Therefore, all polygons with the same reporting unit ID are treated as a single zone.
- When more than one polygon has the same reporting unit ID, the areas for each polygon are combined and metrics are reported as a single record in the Output table.
As the Reporting unit feature is a vector dataset, ArcGIS will perform a vector to raster conversion during processing.
- To better control the vector to raster conversion, the tool defaults the Snap raster and the Processing cell size to that of the Land cover grid. These may be changed from within the tool.
- If a large size disparity exists between the extents of the Reporting unit feature and the Land cover grid, the user may wish to set the Extent in Environment Settings > Processing Extent to the smaller of the two to avoid unnecessary processing.
If the Reporting unit feature has overlapping features, the zonal analysis will be performed for each individual feature.
If a feature in the Reporting unit feature zone data does not overlap any cell centers in the secondary class rasters (e.g.,Land cover grid), those zones will not get converted to the internal zone raster. As a result, those zones will not be represented in the Output table.
The Land cover classification scheme must correspond to the Land cover grid.
- Schemes for common land cover datasets are included with ATtILA. Supplied schemes may be designated as either "ALL" or "LAND" (e.g. NLCD 2001 ALL vs. NLCD 2001 LAND). Schemes designated as "ALL" include all land cover classes in reporting unit area calculations, while those designated as "LAND" include only terrestrial land cover classes, with non-terrestrial land cover classes such as water and snow/ice excluded. More information about each of the classification schemes supplied with ATtILA may be found in Supplied Land Cover Classification Schemas.
- In addition to the common land cover schemes, the tool permits a user-defined land cover classification scheme to be used by specifying a Land cover classification file. Refer to Land Cover Classification for more information on how ATtILA may be customized for user-specific needs.
- NOTE: When a classification scheme with excluded land cover classes is selected, the areas of the excluded classes are disregarded in metric calculations. For example, when selecting a "LAND" classification scheme, the tool will process individual land cover classes and calculate metrics based on the total terrestrial area they occupy within the reporting unit, rather than the percent of the total area within the reporting unit. See Values Element in ATtILA's LCC XML Document and Values Window in the Land Cover Classification Editor for more information on excluded values.
Final output is written to the location specified in the Output table parameter. The Output table may be saved as a File Geodatabase Table, or a dBASE Table.
- NOTE: For most consistent results, it is highly recommended that tool output be saved to a file geodatabase.
- When saving as a File Geodatabase Table, no extension is necessary for the Output table name. The output location must be a file geodatabase.
- When saving as a dBASE Table, include the .dbf extension in the Output table name. dBASE tables may not be saved in a file geodatabase.
When the optional PER CAPITA (square meters of land cover type per individual) selection is checked, the tool allows the user to select a Population raster or polygon feature and a corresponding Population field.
- The Population raster or polygon feature will allow you to choose either a raster, or a polygon feature.
  - When choosing a raster, this tool assumes the grid cell value to be the population count for the grid cell.
  - When choosing a polygon feature, this tool assumes that population is distributed evenly throughout each feature polygon. The tool apportions population by area weighting. For example, if 50% of a population polygon is within a reporting unit, the tool will assign 50% of the value in the polygon's Population field to that reporting unit. Caution should be exercised when population polygons do not have even population distributions as this could result in an overweighting or underweighting of population when the tool performs the apportionment. Generally, greater accuracy will be achieved if the population polygons are smaller than the smallest Reporting unit feature polygons.
  - NOTE: The Population field dropdown is only available when the Population raster or polygon feature is a polygon feature.
  - NOTE: The Population field will default to 'Value' when the Population raster or polygon feature is an integer grid.
  - NOTE: The Population field will be empty when the Population raster or polygon feature is a non-integer grid.
Field names in the Output table follow this naming scheme:
- [class lcpField] or p[class Id] - The percent of the non-excluded reporting unit occupied by the land cover class.
  - [class lcpField] is used if an lcpField attribute is provided in the class's element in the selected Land cover classification file.
    - (e.g., NINDEX for <class Id="NI" Name="All Natural Land Use" filter="" lcpField="NINDEX">)
  - p[class Id] - is used if an lcpField attribute is not provided.
    - (e.g., pNI for <class Id="NI" Name="All Natural Land Use" filter="">)
- When the PER CAPITA option is selected:
  - [class lcpField]_PC or p[class Id]_PC - The area (m²) per person of the land cover class by reporting unit.
- NOTE: Output field names can be altered by editing the Land cover classification file with the Land Cover Classification Editor (Refer to Classes Element in ATtILA's LCC XML Document for general information, or the individual Land cover classification file for details).
- NOTE: The output field name for each class is shown as the second item next to the class's check box in Report metrics for these classes.
In Additional Options, the user may elect to 'Retain Intermediate Layers Generated During Metric Processing', and/or 'Record Process Steps Taken During Metric Calculation'.
- Retain Intermediate Layers Generated During Metric Calculation
  - Choosing INTERMEDIATES retains several of the key intermediate products (e.g., rasters, feature classes, tables) used to generate the final tool output. By examining the intermediate products, the user can gain a better understanding how the metric is calculated. The following intermediate products are listed in the general order they are generated:
    - cwcr_Walk_Line_Merge_# (vector) - A vector feature class created by merging all line features found in Walkable features Only if more than one line feature layers are input into Walkable features.
    - cwcr_Walk_Raster_Line_# (raster) - Only if one or more line feature layers are provided in Walkable features.
    - cwcr_Walk_Poly_Merge_# (vector) - Only if more than one polygon feature layers are provided in Walkable features.
    - cwcr_Walk_Raster_Polygon_# (raster) - Only if one or more polygon feature layers are provided in the Walkable features. The vector converted to raster is either the single input polygon layer or the merged polygon layer
    - cwcr_Walk_Raster_# (raster) -
    - cwcr_Impass_Line_Merge_# (vector) - Only if more than one line feature layers are input into the Impassable features
    - cwcr_Impass_Raster_Line_# (raster) - Only if one or more impassable line features are supplied
    - cwcr_Impass_Poly_Merge_# (vector) - Only if more than one impassable polygon feature layers are supplied
    - cwcr_Impass_Raster_Polygon_# (raster) - Only if a polygon impassable feature layer is supplied
    - cwcr_Impass_Raster_# (raster) -
    - NOTE: To ensure unique filenames, intermediate filenames are typically generated using the CreateScratchName ArcPy function. This function provides a unique name for the intermediate product by appending a number to a filename prefix. The number starts at 0 and is incremented until a unique filename for the output workspace is found. The generated number is represented in this manual by the hashtag (#) symbol.
    - NOTE: The appended number may not be the same for all intermediate products saved during a tool run. Running a tool with different input options can result in different intermediate products being produced. If a tool is run more than once using the same output workspace, different number suffixes may be generated depending on the files already present in the output workspace.
  - Intermediate products are saved to one of the following locations:
    - When the Output table is saved as a File Geodatabase Table, intermediate products are placed in the same file geodatabase.
    - When the Output table is saved as a dBASE Table, a file geodatabase named "attilaScratchWorkspace" is automatically generated in the same output location specified for the Output table. Intermediate products are placed in the attilaScratchWorkspace file geodatabase.
    - NOTE: ATtILA will report the location of the saved intermediate products in the Tool Details' Messages section.
- Record Process Steps Taken During Metric Calculation
  - Choosing LOGFILE will generate a text file containing information on system setup, tool inputs, parameter selections, script operations, and any encountered error or warning messages.
  - Log files will be named, [Output table]_[date_time].txt, with the date represented as YYYYMMDD and time as hh_mm_ss.
  - Where the log file is saved is dependent on the Current Workspace environment setting:
    - When the Current Workspace is a geodatabase, the log file will be located in the folder that contains that workspace.
    - When the Current Workspace is a folder, the log file will be located in that folder.
    - NOTE: In ArcGIS Pro, the default value for the Current Workspace environments is the project default geodatabase.
    - NOTE: ATtILA will report the name and location of the log file in the Tool Details' Messages section.

Syntax

CWCR (Walkable_features, {Impassable_features}, Maximum_travel_distance, Walk_value, Base_value, Output_cost_raster, Cost_raster_cell_size, Snap_raster, {Select_options})

Parameter	Explanation	Data Type
Walkable_features	The vector polygon and/or polyline Feature Layers that defines walkable routes.	Multiple Value
Impassable_features (Optional)	The vector polygon and/or polyline Feature Layers that define impassable features.	Multiple Value
Maximum_travel_distance	The distance where further travel is not possisble. This value is used along with the Cost raster cell size to define the Output cost raster's impassable value in the Output cost raster. Impassable value = (Maximum walking distance / Cost raster cell size) rounded up to the nearest integer. The value units must be a positive integer value.	Long
Walk_value	The cost of traveling through a walkable cell. The value defines the cost of least resistance. The value units must be a positive integer value.	Long
Base_value	The cost of traveling through a walking-resistant cell. The value defines the cost of difficult, but passable, resistance. The value units must be a positive integer value.	Long
Output_cost_raster	The output cost surface raster. It is always an integer raster.	Raster Dataset
Cost_raster_cell_size	The cell size of the output raster that will be created. Units use the linear unit of the geoprocessing outputCoordinateSystem environment setting. If no outputCoordinateSystem is set, the linear unit of the Snap raster's is used.	Double
Snap_raster	The raster that the cell alignment of the Output cost raster will be set to. The Snap raster's linear unit will be used for the Cost raster cell size if no outputCoordinateSystem environment is set.	Raster Layer
Select_options	Tool options available to provide additional information: Retain Intermediate Layers Generated During Metric Calculation - Saves key intermediate products (e.g., rasters, feature classes, tables) used to generate the final tool output. Record Process Steps Taken During Metric Calculation - Saves a log file containing information on tool inputs, selections, and operations.	Multiple Value

Code Samples

Create Walkability Cost Raster example 1 (Python window)

This example generates a cost surface raster where the cell values represent that cell's resistance to movement (1 = easy, 10 = resistant, and 80 = impassable). One line feature layer was entered as input for walkable pathways, while barriers to movement were represented by two line and one polygon feature layers.

import arcpy
from arcpy.sa import *
arcpy.ImportToolbox(r"D:\Destination Folder\ATtILA v{#}.tbx")
from ATtILA2 import metric

Walkable_features = "Roads_Walkable",
Impassable_features = "Roads_NonWalkable;Water_Lines;Water_Polygons",
Maximum_travel_distance = 800,
Walk_value = 1,
Base_value = 10,
Output_cost_raster = r"D:\pyexamples\results.gdb\WalkabilityRaster",
Cost_raster_cell_size = 10,
Snap_raster = r"D:\pyexamples\data.gdb\NLCD_2016",
Select_options = ['INTERMEDIATES  -  Retain Intermediate Layers Generated During Metric Calculation','LOGFILE  -  Record Process Steps Taken During Metric Calculation']

arcpy.ATtILA.CWCR(Walkable_features,
				  Impassable_features,
				  Maximum_travel_distance,
				  Walk_value,
				  Base_value10,
				  Output_cost_raster,
				  Cost_raster_cell_size,
				  Snap_raster,
				  Select_options)

Create Walkability Cost Raster example 2 (Tool Details Messages)

This is a sample capture of the geoprocessing messages generated during a typical tool run. It is provided here to assist in the understanding of the tool's processing steps.


Start Time: Day, Month DD, YYYY hh:mm:ss AM/PM
Created log file: workspace path\\filename
Started: YYYY-MM-DD hh:mm:ss Setting up environment variables
Intermediates are stored in this directory: workspace path
[YYYY-MM-DD hh:mm:ss] Using NLCD_2016's extent for geoprocessing steps.
[YYYY-MM-DD hh:mm:ss] Using NLCD_2016's spatial reference for geoprocessing steps: Albers_Conical_Equal_Area
[YYYY-MM-DD hh:mm:ss] Processing Walkability features
[YYYY-MM-DD hh:mm:ss] Converting Roads_Walkable to raster. Intermediate: cwcr_Walk_Raster_Line_1
[YYYY-MM-DD hh:mm:ss] Setting converted raster cell values to 1 where features exist. Everywhere else will be set to 10. Intermediate: cwcr_Walk_Raster_1
[YYYY-MM-DD hh:mm:ss] Impass Value = 80. Calculated as (Maximum walking distance / Cost raster cell size) rounded up to the nearest integer
[YYYY-MM-DD hh:mm:ss] Processing Impassable features
[YYYY-MM-DD hh:mm:ss] Merging 2 line features from input features. Intermediate: cwcr_Impass_Line_Merge_1
[YYYY-MM-DD hh:mm:ss] Converting cwcr_Impass_Line_Merge_1 to raster. Intermediate: cwcr_Impass_Raster_Line_1
[YYYY-MM-DD hh:mm:ss] Converting Water_Polygons to raster. Intermediate: cwcr_Impass_Raster_Polygon_1
[YYYY-MM-DD hh:mm:ss] Combining converted rasters and setting output cell values to 80 where features exist. Everywhere else will be set to 10. Intermediate: cwcr_Impass_Raster_1
[YYYY-MM-DD hh:mm:ss] Combining the Walkable raster with the Impassable raster for final output
Log file closed
Succeeded at Day, Month DD, YYYY hh:mm:ss AM/PM (Elapsed Time: ##.## units)