NAME
v.net - Performs network maintenance.
KEYWORDS
vector, network, maintenance
SYNOPSIS
v.net
v.net help
v.net [-c] [input=name] [points=name] [output=name] operation=string alayer=string nlayer=string [thresh=float] [file=name] [--overwrite] [--verbose] [--quiet]
Flags:
- -c
- Assign unique categories to new points
- For operation 'nodes'
- --overwrite
- Allow output files to overwrite existing files
- --verbose
- Verbose module output
- --quiet
- Quiet module output
Parameters:
- input=name
- Name of input vector line map (arcs)
- Required for operation 'nodes', 'connect', 'report' and 'nreport'
- points=name
- Name of input vector point map (nodes)
- Required for operation 'connect' and 'arcs'
- output=name
- Name for output vector map
- operation=string [required]
- Operation to be performed
- Options: nodes, connect, arcs, report, nreport
- nodes: new point is placed on each node (line end) if doesn't exist
- connect: connect still unconnected points to vector network by inserting new line(s)
- arcs: new line is created from start point to end point
- report: print to standard output {line_category start_point_category end_point_category}
- nreport: print to standard output {point_category line_category[,line_category...]}
- alayer=string [required]
- Arc layer
- A single vector map can be connected to multiple database tables. This number determines which table to use. When used with direct OGR access this is the layer name.
- Default: 1
- nlayer=string [required]
- Node layer
- A single vector map can be connected to multiple database tables. This number determines which table to use. When used with direct OGR access this is the layer name.
- Default: 2
- thresh=float
- Threshold
- Required for operation 'connect'. Connect points in given threshold.
- file=name
- Name of input file
- Required for operation 'arcs'. '-' for standard input.
DESCRIPTION
v.net is used for network preparation and maintenance.
It permits to insert missing nodes or arcs and to connect unconnected
nodes to the network within a given distance threshold.
It can also report the current network graph status.
In terms of network analysis, a network consists of nodes connected by
arcs. In a vector map prepared for network analysis, nodes are represented
by the grass-internal geometry type node and arcs by the geometry
type line. If a line consists of several vertices and
segments (the typical case), only its staring and ending vertex are
regarded as network nodes. Further more, explicit starting and ending
nodes for e.g. a least costly path search or subnetwork allocation are
represented by the geometry type point.
In general, network analysis will find the least costly (shortest or
fastest) path from point A to point B by follwing the existing lines.
This implies that these points must lie at the start or end point of a
line with is part of the network. If no line is starting or ending at a
given point, this point is not part of the network, i.e. the point is
unconnected and unreachable.
NOTES
If vector editing is required to modify the
graph, wxGUI vector
digitizer or v.edit can be
used. Separately,
Linear Referencing System is available in
GRASS.
EXAMPLES
NC dataset based examples.
Create nodes globally for all line ends and intersections:
v.net input=streams output=streams_node operation=nodes
v.net input=streams points=firestations out=streems_net operation=connect thresh=500
[category of edge] [category of start node] [category of end node]
v.net points=geodetic_swwake_pts output=geodetic_swwake_pts_net operation=arcs file=- << EOF
> 1 28000 28005
> 2 27945 27958
> 3 27886 27897
> EOF
SEE ALSO
wxGUI vector digitizer,
v.edit
v.net.iso,
v.net.path,
v.net.steiner,
v.net.salesman
AUTHORS
Radim Blazek, ITC-irst, Trento, Italy
Martin Landa, FBK-irst (formerly ITC-irst), Trento, Italy and CTU in
Prague, Czech Republic (operation 'connect' and 'arcs')
Last changed: $Date: 2011-12-11 12:12:25 -0800 (Sun, 11 Dec 2011) $
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