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r.clump(1)		    GRASS GIS User's Manual		    r.clump(1)

NAME
       r.clump	 -  Recategorizes  data	in a raster map	by grouping cells that
       form physically discrete	areas into unique categories.

KEYWORDS
       raster, statistics, reclass, clumps

SYNOPSIS
       r.clump
       r.clump --help
       r.clump	[-dg]  input=name[,name,...]   [output=name]	[title=string]
       [threshold=float]      [minsize=integer]	     [--overwrite]    [--help]
       [--verbose]  [--quiet]  [--ui]

   Flags:
       -d
	   Clump also diagonal cells
	   Clumps are also traced along	diagonal neighboring cells

       -g
	   Print only the number of clumps in shell script style

       --overwrite
	   Allow output	files to overwrite existing files

       --help
	   Print usage summary

       --verbose
	   Verbose module output

       --quiet
	   Quiet module	output

       --ui
	   Force launching GUI dialog

   Parameters:
       input=name[,name,...]A [required]
	   Name	of input raster	map(s)

       output=name
	   Name	for output raster map

       title=string
	   Title for output raster map

       threshold=float
	   Threshold to	identify similar cells
	   Valid range:	0 = identical to < 1 = maximal difference
	   Default: 0

       minsize=integer
	   Minimum clump size in cells
	   Clumps smaller than minsize will be merged to form larger clumps
	   Default: 1

DESCRIPTION
       r.clump finds all areas of contiguous cell category  values  (connected
       components)  in	the input raster map. NULL values in the input are ig-
       nored. It assigns a unique category value to each such  area  ("clump")
       in the resulting	output raster map.

       Category	 distinctions  in  the	input  raster map are preserved.  This
       means that if distinct category values are adjacent, they will  NOT  be
       clumped together. The user can run r.reclass prior to r.clump to	recat-
       egorize cells and reassign cell category	values.

       r.clump can also	perform	"fuzzy"	clumping where neighboring cells  that
       are not identical but similar to	each other are clumped together. Here,
       the spectral distance between two cells is scaled to the	range  [0,  1]
       and  compared  to  the  threshold  value. Cells are clumped together if
       their spectral distance is ax threshold.	The result is  very  sensitive
       to  this	 threshold  value, a recommended start value is	0.01, then in-
       creasing	or decreasing this value  according  to	 the  desired  output.
       Once  a suitable	threshold has been determined, noise can be reduced by
       merging small clumps with the minsize option.

       r.clump can also	use multiple raster maps of  any  kind	(CELL,	FCELL,
       DCELL)  as  input. In this case,	the spectral distance between cells is
       used to determine the similarity	of two cells. This  means  that	 input
       maps  must  be  metric: the difference cell 1 - cell 2 must make	sense.
       Categorical maps, e.g. land cover, can not be used in this case.	 Exam-
       ples  for  valid	 inpat maps are	satellite imagery, vegetation indices,
       elevation, climatic parameters etc.

NOTES
       By default, the resulting clumps	are connected only by their  four  di-
       rect  neighbors	(left, right, top, bottom). The	-d flag	activates also
       diagonal	clump tracing.

       r.clump works properly with raster map that contains only  "fat"	 areas
       (more  than  a single cell in width). Linear elements (lines that are a
       single cell wide) may or	may not	be clumped together depending  on  the
       direction of the	line - horizontal and vertical lines of	cells are con-
       sidered to be contiguous, but diagonal lines of cells are  not  consid-
       ered to be contiguous and are broken up into separate clumps unless the
       -d flag is used.

       A random	color table and	other support files are	generated for the out-
       put raster map.

EXAMPLES
       Perform clumping	on "lakes" map (North Carolina sample dataset) and re-
       port area sizes for each	lake individually rather by waterbody type:
       g.region	raster=lakes -p
       # report	sizes by waterbody type
       r.report	lakes units=h
       # clump per raster polygon
       r.clump lakes out=lakes_individual
       # report	sizes by individual waterbody
       r.report	lakes_individual units=h

       Perform fuzzy clumping on Landsat 7 2002	imagery	(North Carolina	sample
       dataset)
       g.region	raster=lsat7_2002_10 -p
       r.clump in=lsat7_2002_10,lsat7_2002_20,lsat7_2002_30,lsat7_2002_40,lsat7_2002_50,lsat7_2002_70 \
	       out=lsat7_2002_clump threshold=0.045
       # reduce	noise
       r.clump in=lsat7_2002_10,lsat7_2002_20,lsat7_2002_30,lsat7_2002_40,lsat7_2002_50,lsat7_2002_70 \
	       out=lsat7_2002_clump_min10 threshold=0.045 minsize=10

SEE ALSO
	  r.average,   r.buffer,  r.distance,  r.grow,	r.mapcalc,  r.mfilter,
       r.neighbors, r.to.vect, r.reclass, r.statistics,	r.support

AUTHOR
       Michael Shapiro,	U.S. Army Construction Engineering Research Laboratory
       Markus Metz (diagonal clump tracing, fuzzy clumping)

SOURCE CODE
       Available at: r.clump source code (history)

       Main index | Raster index | Topics index	| Keywords index  |  Graphical
       index | Full index

       A(C) 2003-2020 GRASS Development	Team, GRASS GIS	7.8.3 Reference	Manual

GRASS 7.8.3							    r.clump(1)

NAME | KEYWORDS | SYNOPSIS | DESCRIPTION | NOTES | EXAMPLES | SEE ALSO | AUTHOR | SOURCE CODE

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