Surface Slope (3D Analyst)
Summary
Creates polygon features that represent ranges of slope values for triangulated surfaces.
Illustration
Usage
-
The surface normal of each triangle, which is given by the vector cross-product of two triangle edges, is used to determine slope in percent or degrees. Percent slope describes the surface normal's ratio of change in height to change in horizontal distance, whereas degree slope is the angle of inclination between the surface normal and a horizontal plane.
Each resulting polygon represents a range of slope values based on the classification breaks used when executing the tool. The default classification breaks divide slope measurements into nine groups and are indicated below:
SLOPE CODE
PERCENT
DEGREE RANGE
1
0.00 — 1.00
0.00 — 0.57
2
1.00 — 2.15
0.57 — 1.43
3
2.15 — 4.64
1.43 — 2.66
4
4.64 — 10.0
2.66 — 5.71
5
10.00 — 21.50
5.71 — 12.13
6
21.50 — 46.40
12.13 — 24.89
7
46.40 — 100.0
24.89 — 45.00
8
100.0 — 1000.0
45.00 — 84.29
9
1000.0 <
84.29 — 90.0
Slope classifications may be customized by specifying a table with up to two fields of numeric values in the Class Breaks Table parameter. The first column identifies the break points of the slope classification. If a second column is provided, its values will be used to associate a code that gets attributed for each polygon feature. If the table below was used, all slope values from 0 to 10 will be represented by a code of 1, 10 to 25 by a code of 2, and so on. The class break units of the table are set in the Slope Units (units) parameter.
CLASS_BREAK
CODE
10.0
1
25.0
2
40.0
3
70.0
4
The table can be in any supported format (.dbf, .txt, or geodatabase table). The name of the fields are irrelevant, as the first will always be used for the class breaks and the second for the aspect codes.
Syntax
| Parameter | Explanation | Data Type |
in_surface |
The TIN, terrain, or LAS dataset whose slope measurements will be written to the output polygon feature. | LAS Dataset Layer; Terrain Layer; TIN Layer |
out_feature_class |
The output feature class. | Feature Class |
units (Optional) |
The units of measure to be used in calculating slope.
| String |
class_breaks_table (Optional) |
A table containing classification breaks that will be used to group the output features. The first column of this table will indicate the break point, whereas the second will provide the classification code. | Table |
slope_field (Optional) |
The field containing slope values. | String |
z_factor (Optional) |
The factor by which Z values will be multiplied. This is typically used to convert Z linear units to match XY linear units. The default is 1, which leaves elevation values unchanged. | Double |
pyramid_level_resolution (Optional) |
The z-tolerance or window-size resolution of the terrain pyramid level that will be used by this tool. The default is 0, or full resolution. | Double |
Code Sample
The following sample demonstrates the use of this tool in the Python window:
import arcpy
from arcpy import env
arcpy.CheckOutExtension("3D")
env.workspace = "C:/data"
arcpy.SurfaceSlope_3d("sample.gdb/featuredataset/terrain", "s_slope.shp", "PERCENT")
The following sample demonstrates the use of this tool in a stand-alone Python script:
'''****************************************************************************
Name: SurfaceSlope Example
Description: This script demonstrates how to use the
SurfaceAspect and SurfaceSlope tools to generate a polygon
that contains the intersection of both
****************************************************************************'''
# Import system modules
import arcpy
from arcpy import env
# Obtain a license for the ArcGIS 3D Analyst extension
arcpy.CheckOutExtension("3D")
# Set environment settings
env.workspace = "C:/data"
try:
# List all TINs in workspace
listTINs = arcpy.ListDatasets("","TIN")
# Determine whether the list contains any TINs
if len(listTINs) > 0:
for dataset in listTINs:
print dataset
# Set Local Variables
aspect = arcpy.CreateUniqueName("Aspect.shp")
slope = arcpy.CreateUniqueName("Slope.shp")
outFC = dataset + "_Aspect_Slope.shp"
#Execute SurfaceAspect
arcpy.SurfaceAspect_3d(dataset, aspect)
#Execute SurfaceSlope
arcpy.SurfaceSlope_3d(dataset, slope)
#Execute SurfaceSlope
print "Starting Intersect"
arcpy.Intersect_analysis(aspect + " #;" + slope + " #", outFC, "ALL")
print "Completed intersect for " + dataset
del aspect, slope, outFC
else:
print "There are no TINs in the " + env.workspace + " directory."
except:
# Returns any other error messages
print arcpy.GetMessages(2)
del arcpy, listTINs