GRASS GIS: v.net.iso

NAME

v.net.iso - Split net by cost isolines
Splits net to bands between cost isolines (direction from centre). Centre node must be opened (costs >= 0). Costs of centre node are used in calculation.

KEYWORDS

vector, networking

SYNOPSIS

v.net.iso
v.net.iso help
v.net.iso [-g] input=name output=name [type=string[,string,...]] [alayer=integer] [nlayer=integer] [afcolumn=string] [abcolumn=string] [ncolumn=string] ccats=range costs=integer[,integer,...] [--overwrite] [--verbose] [--quiet]

Flags:

-g: Use geodesic calculation for longitude-latitude locations
--overwrite: Allow output files to overwrite existing files
--verbose: Verbose module output
--quiet: Quiet module output

Parameters:

input=name: Name of input vector map
output=name: Name for output vector map
type=string[,string,...]: Type; Arc type; Options: line,boundary; Default: line,boundary
alayer=integer: Layer number; Arc layer; Default: 1
nlayer=integer: Layer number; Node layer; Default: 2
afcolumn=string: Arc forward/both direction(s) cost column (number)
abcolumn=string: Arc backward direction cost column (number)
ncolumn=string: Node cost column (number)
ccats=range: Category values; Categories of centres (points on nodes) to which net will be allocated. Layer for this categories is given by nlayer option.
costs=integer[,integer,...]: Costs for isolines

DESCRIPTION

v.net.iso splits net to bands between cost isolines (direction from centre). Centre node must be opened (costs >= 0). Costs of centre node are used in calculation. Supported are cost assignments for both arcs and nodes, and also different in both directions of a vector line. For areas cost will be calculated along boundary lines.

NOTES

Nodes must be on the isolines.

Center nodes have to be assigned to vector nodes. Nodes and arcs can be closed using cost = -1.

EXAMPLE

Subdivision of a network into areas:
The map must contain at least one center (point) on the vector network which can be patched into with v.patch.

# Spearfish

# start node:
echo "591280.5|4926396.0|1" | v.in.ascii out=startnode
g.copy vect=roads,myroads

#connect point to network
v.net myroads points=startnode out=myroads_net op=connect thresh=200

g.region vect=myroads_net
d.mon x0
d.vect myroads_net
d.vect myroads_net col=red icon=basic/triangle fcol=green size=12 layer=2
v.category myroads_net layer=2 op=print

# specify range of center cats (easier to catch all):
v.net.iso input=myroads_net output=myroads_net_iso ccats=1-100000 costs=1000,2000,5000
v.category myroads_net_iso option=report
# ... reports 4 categories:

The network is 4 categories:

cat | distance from point
1          0 - 1000
2       1000 - 2000
3       2000 - 5000
4            > 5000

To see the result, run for example:

g.region n=4928200 s=4922300 w=589200 e=596500
d.erase
d.vect myroads_net_iso
d.vect myroads_net_iso col=blue   cats=1
d.vect myroads_net_iso col=green  cats=2
d.vect myroads_net_iso col=orange cats=3
d.vect myroads_net_iso col=magenta  cats=4
d.vect myroads_net col=red icon=basic/triangle fcol=green size=12 layer=2

AUTHOR

Radim Blazek, ITC-Irst, Trento, Italy
Documentation: Markus Neteler

Last changed: $Date: 2007-08-03 05:33:14 -0700 (Fri, 03 Aug 2007) $

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