Tool Name	Topographic Openness
Tool ID	5
Library ID	ta_lighting
Version	1.0
Author(s)	O.Conrad (c) 2012

Description

Topographic openness expresses the dominance (positive) or enclosure (negative) of a landscape location. See Yokoyama et al. (2002) for a precise definition. Openness has been related to how wide a landscape can be viewed from any position. It has been proven to be a meaningful input for computer aided geomorphological mapping.

References

Anders, N. S., Seijmonsbergen, A. C., Bouten, W. (2009): Multi-Scale and Object-Oriented Image Analysis of High-Res LiDAR Data for Geomorphological Mapping in Alpine Mountains. Proceedings of Geomorphometry 2009. online

Prima, O.D.A, Echigo, A., Yokoyama, R., Yoshida, T. (2006): Supervised landform classification of Northeast Honshu from DEM-derived thematic maps. Geomorphology, vol.78, pp.373-386. doi:10.1016/j.geomorph.2006.02.005

Yokoyama, R., Shirasawa, M., Pike, R.J. (2002): Visualizing topography by openness: A new application of image processing to digital elevation models. Photogrammetric Engineering and Remote Sensing, Vol.68, pp.251-266. online

Parameters

Name	Type	Identifier	Description	Constraints
Input
Elevation	grid, input	DEM
Output
Positive Openness	grid, output	POS
Negative Openness	grid, output	NEG
Options
Radial Limit	floating point number	RADIUS	Maximum search distance [map units].	Minimum: 0.000000 Default: 10000.000000
Directions	choice	DIRECTIONS		Available Choices: [0] single [1] all Default: 1
Direction	floating point number	DIRECTION	Single direction given as degree measured clockwise from the North direction.	Minimum: -360.000000 Maximum: 360.000000 Default: 315.000000
Number of Sectors	integer number	NDIRS		Minimum: 4 Default: 8
Method	choice	METHOD		Available Choices: [0] multi scale [1] line tracing Default: 1
Multi Scale Factor	floating point number	DLEVEL		Minimum: 1.250000 Default: 3.000000
Unit	choice	UNIT		Available Choices: [0] Radians [1] Degree Default: 0
Difference from Nadir	boolean	NADIR	If set, output angles are the mean difference from nadir, or else from a plane.	Default: 1
Processing Buffer Distance	floating point number	PROC_BUFFER	Width of the buffer added around the central raster area [map units]. Tracing is performed across the full buffered extent, but openness is calculated only for the inner (non-buffered) area. The buffer distance should match or exceed the radial limit to avoid edge effects.	Minimum: 0.000000 Default: 0.000000