VfInverseLinear (arcpy.sa)
Summary
Defines the relationship between the vertical cost factor and the vertical relative moving angle through an inverse linear function.
Illustration
 |
VfInverseLinear vertical factor for the PathDistance functions. |
Discussion
The VfInverseLinear object is used in the Spatial Analyst tools Path Distance, Path Distance Allocation, and Path Distance Back Link.
The vertical factor (VF) object defines the relationship between the vertical cost factor and the vertical relative moving angle (VRMA).
VF defines the vertical difficulty encountered in moving from one cell to the next.
VRMA identifies the slope angle between the FROM or processing cell and the TO cell.
The VFs are determined by the inverse values from a straight line in the VRMA-VF coordinate system. The line intercepts the y-axis, equitable to the VF factor, the value associated with the zeroFactor. The slope of the line can be identified if specified with the slope argument.
Syntax
| Parameter | Explanation | Data Type |
zeroFactor |
The zeroFactor will be used to position the y-intercept of the inverse linear function. (The default value is 1.0) | Double |
lowCutAngle |
The VRMA degree defining the lower threshold, below which (less than) the VFs are set to infinity. (The default value is -45.0) | Double |
highCutAngle |
The VRMA degree defining the upper threshold, beyond which (larger than) the VFs are set to infinity. (The default value is 45.0) | Double |
slope |
Identifies the slope of the straight line in the VRMA-VF coordinate system. Slope is specified as the rise/run. For example, a 30-degree slope is 1/30, specified as 0.03333 (rise/run: 1 VF on the y axis / 30 degrees on the x axis); a -45-degree slope as -0.02222. (The default value is -0.022222) | Double |
Properties
| Property | Explanation | Data Type |
| zeroFactor (Read and Write) |
The zeroFactor is used to position the y-intercept for the vertical factor class. | Double |
| lowCutAngle (Read and Write) |
The VRMA degree defining the lower threshold, below which (less than) the VFs are set to infinity. | Double |
| highCutAngle (Read and Write) |
The VRMA degree defining the upper threshold, beyond which (larger than) the VFs are set to infinity. | Double |
| slope (Read and Write) |
Identifies the slope of the straight line in the VRMA-VF coordinate system. Slope is specified as the rise over the run. For example, a 30-degree slope is 1/30, specified as 0.03333 (rise/run: 1 VF on the y axis / 30 degrees on the x axis); a 90-degree slope as 0.011111. | Double |
Code Sample
Demonstrates how to create a VfInverseLinear 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"
myVerticalFactor = VfInverseLinear(1.0, -45, 45, -0.02222)
outPathDist = PathDistance("source.shp", "costraster", "", "", "", "",
myVerticalFactor)
outPathDist.save("C:/sapyexamples/output/pathdistvfil")
Performs a PathDistance analysis using the VfInverseLinear class.
# Name: VfInverseLinear_Ex_02.py
# Description: Uses the VfInverseLinear 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 = "source.shp"
inCostRaster = "costraster"
# Create the VfInverseLinear Object
zeroFactor = 1.0
lowCutAngle = -45
highCutAngle = 45
slope = -0.02222
myVerticalFactor = VfInverseLinear(zeroFactor, lowCutAngle, highCutAngle,
slope)
# Check out the ArcGIS Spatial Analyst extension license
arcpy.CheckOutExtension("Spatial")
# Execute PathDistance
outPathDist = PathDistance(inSourceData, inCostRaster, "", "", "", "",
myVerticalFactor)
# Save the output
outPathDist.save("C:/sapyexamples/output/pathdistvfil2")