SAGA 9.4.2 | Tool Library Documentation

Valley and Ridge Detection (Top Hat Approach)


Description

The tool allows one to calculate fuzzy valley and ridge class memberships from a DEM using the Top Hat approach. The mathematical morphology functions "Opening" and "Closing" form the basis of "The Top Hat Transform" function. The function extracts peaks and valleys with a size condition corresponding to the size of the considered structuring element. Peaks are extracted by the "White Top Hat" (WTH) function: WTH = DEM - Opening >= t Valleys are extracted by the "Black Top Hat" (BTH) function: BTH = Closing - DEM >= t The threshold value "t" works as an additional cut-off to extract only the highest peaks and deepest valleys. This means that the functions permit extracting peaks and valleys based on width and height criterions. For details see the referenced paper. The tool is based on the AML script 'tophat' by Jochen Schmidt, Landcare Research.


References


Parameters

 NameTypeIdentifierDescriptionConstraints
InputElevationgrid, inputDEM--
OutputValley Depthgrid, output, optionalVALLEY--
Hill Heightgrid, output, optionalHILL--
Valley Indexgrid, outputVALLEY_IDX--
Hill Indexgrid, outputHILL_IDX--
Hillslope Indexgrid, output, optionalSLOPE_IDX--
OptionsGrid Systemgrid systemPARAMETERS_GRID_SYSTEM--
Valley Radiusfloating point numberRADIUS_VALLEYThe radius used to fill valleys [map units].Minimum: 0.000000 Default: 1000.000000
Hill Radiusfloating point numberRADIUS_HILLThe radius used to cut hills [map units]Minimum: 0.000000 Default: 1000.000000
Elevation Thresholdfloating point numberTHRESHOLDThe elevation threshold used to identify hills/valleys [map units].Minimum: 0.000000 Default: 100.000000
Slope IndexchoiceMETHODChoose the method to calculate the slope index.Available Choices: [0] default [1] alternative Default: 0

Command Line


Usage: saga_cmd ta_morphometry 24 [-DEM ] [-VALLEY ] [-HILL ] [-VALLEY_IDX ] [-HILL_IDX ] [-SLOPE_IDX ] [-RADIUS_VALLEY ] [-RADIUS_HILL ] [-THRESHOLD ] [-METHOD ]
  -DEM:             	Elevation
	grid, input
  -VALLEY:          	Valley Depth
	grid, output, optional
  -HILL:            	Hill Height
	grid, output, optional
  -VALLEY_IDX:      	Valley Index
	grid, output
  -HILL_IDX:        	Hill Index
	grid, output
  -SLOPE_IDX:       	Hillslope Index
	grid, output, optional
  -RADIUS_VALLEY:	Valley Radius
	floating point number
	Minimum: 0.000000
	Default: 1000.000000
  -RADIUS_HILL:  	Hill Radius
	floating point number
	Minimum: 0.000000
	Default: 1000.000000
  -THRESHOLD:    	Elevation Threshold
	floating point number
	Minimum: 0.000000
	Default: 100.000000
  -METHOD:          	Slope Index
	choice
	Available Choices:
	[0] default
	[1] alternative
	Default: 0