VfCosSec (arcpy.sa)

摘要

通过余弦/正割函数定义垂直成本系数和垂直相对移动角度 (VRMA) 之间的关系。如果 VRMA 为负数，则由余弦函数确定垂直系数，如果 VRMA 为非负数，则由正割函数确定垂直系数。

插图

路径垂直功能的 VfCosSec 垂直系数。

讨论

VfCosSec 对象用于 Spatial Analyst 工具路径距离、路径距离分配和路径距离回溯链接。

垂直系数 (VF) 对象用于定义垂直成本系数和垂直相对移动角度 (VRMA) 之间的关系。

VF 用于定义从一个像元移至下一像元的垂直阻力。

VRMA 用于确定“起始”像元或处理像元与“终止”像元之间的坡度角。

当 VRMA 度数为负值时，VF 由 VRMA 的余弦函数确定。如 VRMA 度数为正值，VF 则由 VRMA 的正割函数确定。

语法

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

参数	说明	数据类型
lowCutAngle	The VRMA degree defining the lower threshold, below which (less than) the VFs are set to infinity. (默认值为 -90.0)	Double
highCutAngle	The VRMA degree defining the upper threshold, beyond which (larger than) the VFs are set to infinity. (默认值为 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 (默认值为 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 (默认值为 1.0)	Double

属性

属性	说明	数据类型
lowCutAngle (读写)	The VRMA degree defining the lower threshold, below which (less than) the VFs are set to infinity.	Double
highCutAngle (读写)	The VRMA degree defining the upper threshold, beyond which (larger than) the VFs are set to infinity.	Double
cosPower (读写)	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 (读写)	The power to which the values in the secant VRMA function will be raised. The VF is determined by: VF = sec(VRMA)power	Double

代码实例

VfCosSec 示例 1（Python 窗口）

演示如何创建 VfCosSec 类以及如何在 Python 窗口的 PathDistance 工具中使用该类。

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 示例 2（独立脚本）

使用 VfCosSec 类执行 PathDistance 分析。

# 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")