GRASS GIS: m.disline

NAME

m.disline - dissolving small linear entities

KEYWORDS

vector, line, dissolve

SYNOPSIS

m.disline
m.disline help
m.disline [-i] input=name output=name length=float [unit=string] [columnp=string] [valuep=string] [--overwrite] [--verbose] [--quiet]

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
length=float: min length value
unit=string: units (meters(me), kilometers(k)); Options: me,k; 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.disline allows the user to dissolve small linear entities with user's threshold (length parameter). Flag i prints only statistics (see Examples for details). Columnp and valuep can be used to treat separately particular entities (e.g. pipe entities can be dissolve only with pipe entities), see Examples for details.

NOTES

Dangle segments are removed (as in v.clean tool=rmdangle command).

Confluence integrity is preserved : in the following example, on the left figure, in the input layer, length of the segment 2 is under the user's threshold and should be merged on segment 4 which is its longest neighbour. But in order to preserve geometry confluence, segment 2 is merged on segment 1, as seen on the right figure in the output layer.

Input layer (left) ; Output layer (right)

EXAMPLES

Print Statistics

Print Statistics for dissolving linear entities for the line1 vector map (threshold is 200 meters)

GRASS 6.3.0 :~ > m.disline -i input=line1 output=line2 length=200 unit=me
You choose a minimum length of 200 m
 For the vector line1,
 the dissolving small linear entities operation will work
 on 8 lines for 32 total lines
 and will represent 3.5 % of the total length

Dissolving linear entities

Dissolving linear entities for the line1 vector map (threshold is 200 meters)

GRASS 6.3.0 :~ > m.disline input=line1 output=line2 length=200 unit=me

Particular entities treatment

Dissolving small linear entities for the network1 vector map (threshold is 100 meters) and separate treatment for particular entities defined by the column 'type' and the value 'pipe'

GRASS 6.3.0 :~ > m.disline input=network1 output=network2 length=100 unit=me columnp=type valuep=pipe

In the following figure, pipe segments are in grey color and segment nodes are represented by circles. In the output layer (on right figure), small segments with the same attribut (which length is under user's threshold) are dissolved; pipe segments can be preserved if they have no pipe neighbours.

Input network1 layer (left) ; Output network2 layer (right)

AUTHORS

Michael Rabotin, UMR LISAH, Montpellier, France

rabotin@supagro.inra.fr

Last Changed: 23 January 2012

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