NAME¶

v.net - Performs network maintenance.

KEYWORDS¶

vector, networking, maintenance

SYNOPSIS¶

v.net v.net help v.net [-c] input=name [points=name] [output=name] [operation=string] [alayer=integer] [nlayer=integer] [thresh=float] [--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 map

points=name

 

Name of input point vector map

 

Required for operation 'connect'

output=name

 

Name for output vector map

operation=string

 

Operation to be performed

 

Options: nodes,connect,report,nreport

 

Default: nodes

 

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)

 

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=integer

 

Arc layer

 

A single vector map can be connected to multiple database tables. This number determines which table to use.

 

Default: 1

nlayer=integer

 

Node layer

 

A single vector map can be connected to multiple database tables. This number determines which table to use.

 

Default: 2

thresh=float

 

Threshold

 

Required for operation 'connect'. Connect points in given threshold.

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 starting and ending vertex are regarded as network nodes. Further more, explicit starting and ending nodes for e.g. least cost path search or subnetwork allocation are represented by the geometry type point which must be identical with the start or end vertex (network node) of a line. 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 the points A, B 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, v.digit or v.edit can be used. Separately, Linear Referencing System is available in GRASS.

EXAMPLES¶

Spearfish based examples: Create nodes globally for all line ends and intersections: v.net input=roads output=roads_node operation=nodes Merge in nodes from a separate map within given threshold: echo "1|601955.1|4916944.9|start 2|594385.6|4921565.2|end" | v.in.ascii in=- cat=1 x=2 y=3 out=startend col="cat integer, \
east double precision, north double precision, label varchar(6)" #create lines map connecting points to network (on layer 2) v.net myroads points=startend out=myroads_net op=connect thresh=200

SEE ALSO¶

v.digit, 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, Trento, Italy Last changed: $Date: 2011-11-14 09:27:31 +0100 (Mon, 14 Nov 2011) $ Full index © 2003-2011 GRASS Development Team