VfCosSec

Disponible avec une licence Spatial Analyst.

Synthèse

Defines the relationship between the vertical cost factor and the vertical relative moving angle (VRMA) through a cosine/secant function. If the VRMA is negative the vertical factor is defined by a cosine function, and if the VRMA is nonnegative the vertical factor is defined by a secant function.

Illustration

Graph of the cosine secant 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.

When the VRMA is a negative degree value, the VF is determined by the cosine function of the VRMA. If the VRMA is a positive degree value, the VF is determined by the secant function of the VRMA.

Syntaxe

VfCosSec ({lowCutAngle}, {highCutAngle}, {cosPower}, {secPower})

Paramètre	Explication	Type de données
lowCutAngle	The VRMA degree defining the lower threshold, below which (less than) the VFs are set to infinity. (La valeur par défaut est -90.0)	Double
highCutAngle	The VRMA degree defining the upper threshold, beyond which (larger than) the VFs are set to infinity. (La valeur par défaut est 90.0)	Double
cosPower	The power to which the values in the cosine VRMA function will be raised. The VF is determined by: VF = cos(VRMA)power (La valeur par défaut est 1.0)	Double
secPower	The power to which the values in the secant VRMA function will be raised. The VF is determined by: VF = sec(VRMA)power (La valeur par défaut est 1.0)	Double

Propriétés

Propriété	Explication	Type de données
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
cosPower (Lecture et écriture)	The power to which the values in the cosine VRMA function will be raised. The VF is determined by: VF = cos(VRMA)power	Double
secPower (Lecture et écriture)	The power to which the values in the secant VRMA function will be raised. The VF is determined by: VF = sec(VRMA)power	Double

Exemple de code

VfCosSec example 1 (Python window)

Demonstrates how to create a VfCosSec 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 = VfCosSec(-90, 90, 1, 1)
outDistAccum = DistanceAccumulation("Source.shp", "", "elev.tif",
                                   "cost.tif", "elev.tif",
                                    myVerticalFactor)
outDistAccum.save("C:/sapyexamples/output/distAccumVfCS.tif")

VfCosSec example 2 (stand-alone script)

Performs a DistanceAccumulation analysis using the VfCosSec class.

# Name: VfCosSec_Ex_02.py
# Description: Uses the VfCosSec 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 VfCosSec Object
lowCutAngle = -90
highCutAngle = 90
cosPower = 1
secPower = 1
myVerticalFactor = VfCosSec(lowCutAngle, highCutAngle, cosPower, secPower)

# 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/distaccumvfCS2.tif")