NAME

KEYWORDS

SYNOPSIS

Flags:

-i

print only statistics (no calcul) and exit

--overwrite

Allow output files to overwrite existing files

--verbose

Verbose module output

--quiet

Quiet module output

Parameters:

input=name

Input vector name

output=name

Output vector name

area=float

minimum area value

unit=string

units (meters (me), kilometers (k), acres (a), hectares (h))

Options: me,k,a,h

Default: me

columnp=string

Name of column used to treat particular entities (column must exist)

valuep=string

value used in 'columnp' to identify the particular entities

DESCRIPTION

m.dispolyg allows the user to dissolve small areal entities with user's threshold (area parameter). Flag i prints only statistics (see Examples for details). Columnp and valuep can be used to treat separately particular entities (e.g. road entities can be dissolved only with road entities), see Examples for details.

NOTES

Small areal entities are dissolved to the neighouring entity with whom they share the longest boundary. The dissolving process is iterative (process is stopped when no more small entity is found). Small areal entities under the threshold but with no neighbours are preserved.

EXAMPLES

Print statistics

Print statistics for dissolving areal entities for the polygon1 vector map (threshold is 1200 square meters)

GRASS 6.3.0 :~ > m.dispolyg -i input=polygon1 output=polygon2 area=1200 unit=me
You choose a minimum area of 1200 m2
 For the vector polygon1,
 the dissolving small area entities operation will work
 on 6 polygons for 28 total polygons
 and will represent 4.3 % of the total surface

Dissolving areal entities

Dissolving areal entities for the polygon1 vector map (threshold is 1200 square meters)

GRASS 6.3.0 :~ > m.dispolyg input=polygon1 output=polygon2 area=1200 unit=me

Input polygon1 layer (left) ; Output polygon2 layer (right)

Particular entities treatment

Dissolving small areal entities for the plot1 vector map (threshold is 100 square meters) and separate treatment for particular entities defined by the column 'type' and the value 'road'

GRASS 6.3.0 :~ > m.dispolyg input=plot1 output=plot2 area=100 unit=me columnp=type valuep=road

Input plot1 layer (left) ; Output plot2 layer (right)

SEE ALSO

m.disline

AUTHORS

Michael Rabotin, UMR LISAH, Montpellier, France

rabotin@supagro.inra.fr

Last Changed: 21 July 2010

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