TopographicFeatures Task

This task calculates topographic features on an input DEM. The result is a classification image of different terrain types or morphometric features such as peak, ridge, pass, plane, channel, or pit.

Example

; Start the application

e = ENVI()

; Open an input file

File = Filepath('bhdemsub.img', SUBDIR=['classic','data'], $

ROOT_DIR=e.Root_Dir)

Raster = e.OpenRaster(File)

; Get the task from the catalog of ENVITasks

Task = ENVITask('topographicFeatures')

; Define inputs

Task.INPUT_RASTER = Raster

; Run the task

Task.Execute

; Get the data collection

dataColl = e.Data

; Add the output to the data collection

dataColl.Add, Task.OUTPUT_RASTER

; Display the result

View = e.GetView()

Layer = View.CreateLayer(Task.OUTPUT_RASTER)

Syntax

Result = ENVITask('TopographicFeatures')

Input properties (Set, Get): CURVATURE_TOLERANCE, FEATURES, INPUT_RASTER, KERNEL_SIZE, OUTPUT_RASTER_URI, PIXEL_SIZE, SLOPE_TOLERANCE

Output properties (Get only): OUTPUT_RASTER

Properties marked as "Set" are those that you can set to specific values. You can also retrieve their current values any time. Properties marked as "Get" are those whose values you can retrieve but not set.

Methods

This task inherits the following methods from ENVITask:

Properties

This task inherits the following properties from ENVITask:

COMMUTE_ON_DOWNSAMPLE

CURVATURE_TOLERANCE (optional)

Specify the curvature tolerance. The default value is 0.1. For a pixel to be classified as a peak, pit, or pass, the slope value must be less than the slope tolerance and the cross-sectional curvature must be greater than the curvature tolerance. Increasing the slope tolerance and decreasing the curvature tolerance increases the number of peaks, pits, and passes in the classified output.

FEATURES (optional)

Specify a string array with the features to classify. By default, all features will be included.

Peak: A surface with a convex cross-section and a convex longitudinal curvature
Ridge: A sloping surface that is convex in the cross-sectional direction
Pass: A surface with one convex curvature and one concave curvature
Plane: A surface of constant elevation
Channel: A sloping surface that is concave in the cross-sectional direction
Pit: A surface with a concave curvature

INPUT_RASTER (required)

Specify a raster on which to calculate topographic features.

KERNEL_SIZE (optional)

Specify the size of the kernel used for processing. The default value is 3.

OUTPUT_RASTER

This is a reference to the output raster of filetype ENVI.

OUTPUT_RASTER_URI (optional)

Specify a string with the fully qualified filename and path of the associated OUTPUT_RASTER. If you do not specify this property, or set it to an exclamation symbol (!), a temporary file will be created.

PIXEL_SIZE (optional)

Specify a double-precision array with the X and Y pixel size of the input raster, in meters.

SLOPE_TOLERANCE (optional)

Specify the slope tolerance. The default value is 1.0.

For a pixel to be classified as a peak, pit, or pass, the slope value must be less than the slope tolerance and the cross-sectional curvature must be greater than the curvature tolerance. Increasing the slope tolerance and decreasing the curvature tolerance increases the number of peaks, pits, and passes in the classified output.

Version History

ENVI 5.5

Introduced

API Version

4.2