Surface Aspect (3D Analyst Tools)

Summary

Creates polygon features that represent aspect measurements derived from a TIN, terrain, or LAS dataset surface.

Illustration

TIN Aspect illustration

Usage

Aspect represents the horizontal orientation of a surface and is determined in units of degrees. Each facet of the surface is assigned a code value which represents the cardinal or ordinal direction of its slope, and contiguous areas with the same code are merged into one feature. The default classification scheme is defined as follows:


Code	Slope Direction	Slope Angle Range
-1	Flat	No Slope
1	North	0° – 22.5°
2	Northeast	22.5° – 67.5°
3	East	67.5° – 112.5°
4	Southeast	112.5° – 157.5°
5	South	157.5° – 202.5°
6	Southwest	202.5° – 247.5°
7	West	247.5° – 292.5°
8	Northwest	292.5° – 337.5°
9	North	337.5° – 360°

Customized class definitions can be provided through a Class Breaks Table. The table must have two columns where the first indicates the aspect break point in degrees and the second defines its code value. Consider the following example:

Break

Aspect_Code

90.0

1

180.0

2

270.0

3

360.0

4

Note:

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.

Break	Aspect_Code
90.0	1
180.0	2
270.0	3
360.0	4

Label	Explanation	Data type
Input Surface	The TIN, terrain, or LAS dataset surface that will be processed.	LAS Dataset Layer; Terrain Layer; TIN Layer
Output Feature Class	The feature class that will be produced.	Feature Class
Class Breaks Table (Optional)	A table containing the classification breaks that will be used to define the aspect ranges in the output feature class.	Table
Aspect Field (Optional)	The field containing aspect code values.	String
Pyramid Level Resolution (Optional)	The z-tolerance or window-size resolution of the terrain pyramid level that will be used. The default is 0, or full resolution.	Double

arcpy.3d.SurfaceAspect(in_surface, out_feature_class, {class_breaks_table}, {aspect_field}, {pyramid_level_resolution})

Name	Explanation	Data type
in_surface	The TIN, terrain, or LAS dataset surface that will be processed.	LAS Dataset Layer; Terrain Layer; TIN Layer
out_feature_class	The feature class that will be produced.	Feature Class
class_breaks_table (Optional)	A table containing the classification breaks that will be used to define the aspect ranges in the output feature class.	Table
aspect_field (Optional)	The field containing aspect code values.	String
pyramid_level_resolution (Optional)	The z-tolerance or window-size resolution of the terrain pyramid level that will be used. The default is 0, or full resolution.	Double

Code sample

SurfaceAspect example 1 (Python window)

The following sample demonstrates the use of this tool in the Python window:

arcpy.env.workspace = "C:/data"
arcpy.ddd.SurfaceAspect("sample.gdb/featuredataset/terrain", "terrain_aspect.shp")

SurfaceAspect example 2 (stand-alone script)

The following sample demonstrates the use of this tool in a stand-alone Python script:

'''****************************************************************************
Name: SurfaceAspect 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

# Set environment settings
arcpy.env.workspace = "C:/data"

# 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"
        # Run SurfaceAspect
        arcpy.ddd.SurfaceAspect(dataset, aspect)
        # Run SurfaceSlope
        arcpy.ddd.SurfaceSlope(dataset, slope)
        # Run SurfaceSlope
        print("Starting Intersect")
        arcpy.analysis.Intersect(aspect + " #;" + slope + " #", outFC, "ALL")
        print("Completed intersect for " + dataset)
else:
    print("There are no TINs in the " + arcpy.env.workspace + " directory.")

Environments

Current Workspace, Output Coordinate System, Geographic Transformations, Extent, XY Resolution, XY Tolerance, Output XY Domain, Output CONFIG Keyword, Auto Commit, Minimize memory use during analysis on terrains

Licensing information

Basic: Requires 3D Analyst
Standard: Requires 3D Analyst
Advanced: Requires 3D Analyst