Topographic Openness

Author: O.Conrad (c) 2012
Menu: Terrain Analysis | Lighting and Visibility

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`	-	-
Output	Negative Openness	grid, output	`NEG`	-	-
Options	Grid System	grid system	`PARAMETERS_GRID_SYSTEM`	-	-
	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

Command Line


Usage: saga_cmd ta_lighting 5 [-DEM ] [-POS ] [-NEG ] [-RADIUS ] [-DIRECTIONS ] [-DIRECTION ] [-NDIRS ] [-METHOD ] [-DLEVEL ] [-UNIT ] [-NADIR ] [-PROC_BUFFER ]
  -DEM:              Elevation
	grid, input
  -POS:              Positive Openness
	grid, output
  -NEG:              Negative Openness
	grid, output
  -RADIUS:        Radial Limit
	floating point number
	Minimum: 0.000000
	Default: 10000.000000
  -DIRECTIONS:       Directions
	choice
	Available Choices:
	[0] single
	[1] all
	Default: 1
  -DIRECTION:
                          Direction
                          	floating point number
                          	Minimum: -360.000000
                          	Maximum: 360.000000
                          	Default: 315.000000
  -NDIRS:            Number of Sectors
	integer number
	Minimum: 4
	Default: 8
  -METHOD:           Method
	choice
	Available Choices:
	[0] multi scale
	[1] line tracing
	Default: 1
  -DLEVEL:        Multi Scale Factor
	floating point number
	Minimum: 1.250000
	Default: 3.000000
  -UNIT:             Unit
	choice
	Available Choices:
	[0] Radians
	[1] Degree
	Default: 0
  -NADIR:            Difference from Nadir
	boolean
	Default: 1
  -PROC_BUFFER:   Processing Buffer Distance
	floating point number
	Minimum: 0.000000
	Default: 0.000000