VfInverseLinear

Disponible avec une licence Spatial Analyst.

Synthèse

Defines the relationship between the vertical cost factor and the vertical relative moving angle through an inverse linear function.

Illustration

Graph of the inverse linear vertical factor.

Discussion

This object is used in the Distance Accumulation and Distance Allocation Spatial Analyst tools, as well as the Path Distance, Path Distance Allocation, and Path Distance Back Link Legacy Distance tools.

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.

Syntaxe

VfInverseLinear ({zeroFactor}, {lowCutAngle}, {highCutAngle}, {slope})

Paramètre	Explication	Type de données
zeroFactor	The zeroFactor will be used to position the y-intercept of the inverse linear function. (La valeur par défaut est 1.0)	Double
lowCutAngle	The VRMA degree defining the lower threshold, below which (less than) the VFs are set to infinity. (La valeur par défaut est -45.0)	Double
highCutAngle	The VRMA degree defining the upper threshold, beyond which (larger than) the VFs are set to infinity. (La valeur par défaut est 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. (La valeur par défaut est -0.022222)	Double

Propriétés

Propriété	Explication	Type de données
zeroFactor (Lecture et écriture)	The zeroFactor is used to position the y-intercept for the vertical factor class.	Double
lowCutAngle (Lecture et écriture)	The VRMA degree defining the lower threshold, below which (less than) the VFs are set to infinity.	Double
highCutAngle (Lecture et écriture)	The VRMA degree defining the upper threshold, beyond which (larger than) the VFs are set to infinity.	Double
slope (Lecture et écriture)	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

Exemple de code

VfInverseLinear example 1 (Python window)

Demonstrates how to create a VfInverseLinear class and use it in the DistanceAccumulation 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)
outDistAccum = DistanceAccumulation("Source.shp", "", "elev.tif",
                                   "cost.tif", "elev.tif",
                                    myVerticalFactor)
outDistAccum.save("C:/sapyexamples/output/distAccumVfIL.tif")

VfInverseLinear example 2 (stand-alone script)

Performs a DistanceAccumulation analysis using the VfInverseLinear class.

# Name: VfInverseLinear_Ex_02.py
# Description: Uses the VfInverseLinear object to run the 
#              DistanceAccumulation 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.tif"
inElevation = "elev.tif"

# 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
outDistAccum = DistanceAccumulation(inSourceData, "", inElevation,
                                    inCostRaster, inElevation,
                                    myVerticalFactor)

# Save the output 
outDistAccum.save("C:/sapyexamples/output/distaccumvfIL2.tif")