r.reclass.area.py - GRASS manual

NAME

r.reclass.area.py - Reclasses a raster map greater or less than user specified area size (in hectares).

KEYWORDS

SYNOPSIS

r.reclass.area.py

r.reclass.area.py --help

r.reclass.area.py [-cdimv] input=name output=name [value=float] [mode=string] [lower=float] [upper=float] [method=string] [--overwrite] [--help] [--verbose] [--quiet] [--ui]

Flags:

-c: Input map is clumped
-d: Generate clumps including diagonal neighbors
-i: Invert filter (remove clumps larger than lower and smaller than upper)
-m: Apply lower area threshold as "minsize" during clumping
-v: Output vector map, do not convert back to raster (only for method 'rmarea')
--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 [required]: Name of input raster map
output=name [required]: Name for output raster map
value=float: Value option that sets the area size limit (in hectares) (deprecated)
mode=string: Keep only areas lesser or greater than specified value (deprecated); Options: lesser, greater
lower=float: Value for the lower area size limit (in hectares). Pixel clumps with areas below this value are removed.
upper=float: Value for the upper area size limit (in hectares). Pixel clumps with areas above this value are removed.
method=string: Method used for area size filtering; Options: reclass, rmarea; Default: reclass

DESCRIPTION
EXAMPLES
SEE ALSO
AUTHORS

DESCRIPTION

r.reclass.area removes areas (pixel clumps) from a raster map that are smaller than a user specified lower area size and/or greater than a user-specified upper threshold (both in hectares). r.reclass.area provides two methods for filtering:

reclass - raster-based filtering
rmarea - vector-based filtering

With the reclass method, the input raster map is clumped and then reclassified using the clump size. With the -m flag, reclass method will remove small areas already during clumping, using the minsize option there. If the -c flag is used, r.reclass.area will skip the creation of a clumped raster and assume that the input raster map is already clumped. The rmarea method converts the raster map to vector and removes areas outside the given thresholds using v.clean and v.edit. With the -v flag the output is the filtered vector map instead of a raster. An important difference between the two methods with regard to the lower area size threshold is that method=reclass deletes these areas, whereas method=rmarea tries to merge these small areas with a neighbouring larger area if existing. Details are explained in v.clean describing the behaviour of tool=rmarea.

EXAMPLES

In this example, the ZIP code map in the North Carolina sample dataset is filtered for large areas (removing smaller areas from the map).

g.region raster=zipcodes -p
r.report zipcodes unit=h

Extract only areas greater than 2000 ha, NULL otherwise:

r.reclass.area input=zipcodes output=zipcodes_larger2000ha greater=2000

r.report zipcodes_larger2000ha unit=h

Figure: r.reclass.area method=reclass

In this example, the ZIP code map in the North Carolina sample dataset is filtered for smaller areas which are substituted with the value of the respective adjacent area with largest shared boundary. Reclass by substitutional removing of areas smaller than 1000 ha:

r.reclass.area input=zipcodes output=zipcodes_minor1000ha mode=lesser value=1000 method=rmarea

Figure: r.reclass.area method=rmarea

AUTHORS

NRCS,
Markus Neteler,
Stefan Blumentath

SOURCE CODE

Available at: r.reclass.area source code (history)

Latest change: Friday Aug 07 20:45:33 2026 in commit: 0850a40412c109476e3551dd90a17c99e45908ff