HfForward
摘要
Defines the relationship between the horizontal cost factor and the horizontal relative moving angle through a forward function. The function establishes that only forward movement is allowed.
插图
讨论
The HfForward object is used in the Spatial Analyst tools Path Distance, Path Distance Allocation, and Path Distance Back Link.
If a horizontal relative moving angle (HRMA) is less than 45 degrees for a section of travel, the horizontal factor (HF) is set to the value associated with the zeroFactor. When the HRMA is larger than or equal to 45 degrees and less than 90 degrees, the HF is set to the sideValue. If the HRMA is equal to or greater than 90 degrees, the HF is set to infinity.
语法
参数 | 说明 | 数据类型 |
zeroFactor |
The zeroFactor will be used to position the y-intercept of the forward function. (默认值为 0.5) | Double |
sideValue |
Identifies the HF value that will be assigned for HRMAs that are equal to or less than 45 degrees and less than 90 degrees. In the diagram above, the sideValue is assigned 1. (默认值为 1.0) | Double |
属性
属性 | 说明 | 数据类型 |
zeroFactor (可读写) |
The zeroFactor will be used to position the y-intercept of the function. The zeroFactor is assigned as the horizontal factor when HRMA is less then the cut angle. | Double |
sideValue (可读写) |
Identifies the HF value that will be assigned for HRMAs that are equal to or less than 45 degrees and less than 90 degrees. In the diagram above the sideValue is assigned 1. | Double |
代码示例
Demonstrates how to create an HfForward class and use it in the PathDistance tool within the Python window.
import arcpy from arcpy import env from arcpy.sa import * env.workspace = "C:/sapyexamples/data" myHorizFactor = HfForward(0.5, 1.0) outPathDist = PathDistance("sourcepts.shp", "costraster", "", "", myHorizFactor) outPathDist.save("C:/sapyexamples/output/pathdisthff")
Performs a PathDistance analysis using the HfForward class.
# Name: HfForward_Ex_02.py # Description: Uses the HfForward object to execute the PathDistance tool. # 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 inSourceData = "sourcepts.shp" inCostRaster = "costraster" # Create the HfForward Object zeroFactor = 0.5 sideValue = 1.0 myHorizFactor = HfForward(zeroFactor, sideValue) # Check out the ArcGIS Spatial Analyst extension license arcpy.CheckOutExtension("Spatial") # Execute PathDistance outPathDist = PathDistance(inSourceData, inCostRaster, "", "", myHorizFactor) # Save the output outPathDist.save("C:/sapyexamples/output/pathdisthff2")