ArcGIS Help 10.1 - VfCosSec (arcpy.sa)

Zusammenfassung

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.

Bild

VfCosSec vertical factor for the PathDistance functions.

Diskussion

The VfCosSec 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.

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.

Syntax

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

Parameter	Erläuterung	Datentyp
lowCutAngle	The VRMA degree defining the lower threshold, below which (less than) the VFs are set to infinity. (Der Standardwert ist -90.0)	Double
highCutAngle	The VRMA degree defining the upper threshold, beyond which (larger than) the VFs are set to infinity. (Der Standardwert ist 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 (Der Standardwert ist 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 (Der Standardwert ist 1.0)	Double

Eigenschaften

Eigenschaft	Erläuterung	Datentyp
lowCutAngle (Lesen und schreiben)	The VRMA degree defining the lower threshold, below which (less than) the VFs are set to infinity.	Double
highCutAngle (Lesen und schreiben)	The VRMA degree defining the upper threshold, beyond which (larger than) the VFs are set to infinity.	Double
cosPower (Lesen und schreiben)	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 (Lesen und schreiben)	The power to which the values in the secant VRMA function will be raised. The VF is determined by: VF = sec(VRMA)power	Double

Codebeispiel

VfCosSec example 1 (Python window)

Demonstrates how to create a VfCosSec 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 = VfCosSec(-90, 90, 1, 1)
outPathDist = PathDistance("source.shp", "costraster", "", "", "", "",
                           myVerticalFactor)
outPathDist.save("C:/sapyexamples/output/pathdistvsc")

VfCosSec example 2 (stand-alone script)

Performs a PathDistance analysis using the VfCosSec class.

# Name: VfCosSec_Ex_02.py
# Description: Uses the VfCosSec 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 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
outPathDist = PathDistance(inSourceData, inCostRaster, "", "", "", "",
                           myVerticalFactor)

# Save the output 
outPathDist.save("C:/sapyexamples/output/pathdistvsc2")