GRASS GIS: m.dispolygseg

NAME

m.sliverpolygseg - dissolving sliver entities with hierarchical level after segmentation (use Gravelius Index)

KEYWORDS

vector, selective dissolve, areal, hierarchical order, sliver

SYNOPSIS

m.sliverpolygseg
m.sliverpolygseg help
m.sliverpolygseg [-i] input=name output=name index=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
index=float: gravelius INDEX max value; (in general, features with index > 1.6 are considered sliver features)
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 protect particular entities (column must exist)
valuep=string: value used in 'columnp' to identify the particular entities

DESCRIPTION

m.sliverpolygseg allows the user to dissolve sliver areal entities (using Gravelius Index) with user's threshold (index parameter) and with hierarchical order. The input layer must be created by m.seg script. 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. To treat particular entities, m.colseg script must be used to patch attribute column to identify entities.

NOTES

Sliver areal entities are dissolved to the neighouring entity with whom they share the longest boundary and whom have the lowest hierarchical order (selective cleaning procedure). Hierarchical order is defined by m.seg script and is provided by the attribute table(s)s of the input vector data. The dissolving process is iterative (process is stopped when no more small entity is found). Sliver areal entities superior to threshold but with no neighbours are preserved.

EXAMPLES

Print statistics for dissolving sliver areal entities for the seg1 vector map (threshold is 2)

GRASS 6.3.0 :~ > m.sliverpolygseg -i input=seg1 output=seg2 index=2 unit=me
You choose a maximum gravelius index of 2
 For the vector seg1,
 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 sliver areal entities

Dissolving sliver areal entities for the seg1 vector map (threshold is 2)

GRASS 6.3.0 :~ > m.sliverpolygseg input=seg1 output=seg2 index=2 unit=me

Particular entities treatment

Dissolving sliver areal entities for the seg1 vector map (threshold is 2) and separate treatment for particular entities defined by the column 'type' and the value 'road'. Using m.colseg script to patch attribute columns from field vector input data.

GRASS 6.3.0 :~ > m.colseg input=seg1 output=seg1p polygon=field columns=type
GRASS 6.3.0 :~ > m.sliverpolygseg input=seg1p output=seg2 index=2 unit=me columnp=type valuep=road

REFERENCES

Gravelius, H. (1914) GrundriB der gesamten Gewasserkunde, Band 1: FluBkunde (Compendium of Hydrology, vol. 1: Rivers, in German). Goschen, Berlin, Germany.

AUTHORS

Michael Rabotin, UMR LISAH, Montpellier, France

rabotin@supagro.inra.fr

Last Changed: 21 July 2010

Main index