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NAME

v.net.steiner - Create Steiner tree for the network and given terminals
Note that 'Minimum Steiner Tree' problem is NP-hard and heuristic algorithm is used in this module so the result may be sub optimal

KEYWORDS

vector, networking

SYNOPSIS

v.net.steiner
v.net.steiner help
v.net.steiner [-g] input=name output=name [type=string[,string,...]] [alayer=integer] [nlayer=integer] [acolumn=string] tcats=range [nsp=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 (used for terminals)
Default: 2
acolumn=string
Arcs' cost column (for both directions)
tcats=range
Category values
Categories of points on terminals (layer is specified by nlayer)
nsp=integer
Number of steiner poins (-1 for all possible)
Default: -1

DESCRIPTION

v.net.steiner calculates the optimal connection of nodes on a vector network.

A Steiner tree is used to calculate the minimum-cost vector network connecting some number of end nodes in a network framework. For example it could be used to find the path following a road system which will minimize the amount of fibre optic cable needed to connect a series of satellite offices.

EXAMPLE

Steiner tree for for 6 digitized nodes (Spearfish):
g.copy vect=roads,myroads
v.db.addcol myroads col="cost double precision"

# define traveling costs as inverse of speed limit:
v.db.update myroads col=cost val=1/50
v.db.update myroads col=cost val=1/75 where="label='interstate'"
v.db.update myroads col=cost val=1/5 where="label='unimproved road'"
v.db.update myroads col=cost val=1/25 where="label='light-duty road, improved surface'"
v.db.select myroads

# we have 6 locations to allocate
echo "1|601653.5|4922869.2|a
2|608284|4923776.6|b
3|601845|4914981.9|c
4|596270|4917456.3|d
5|593330.8|4924096.6|e
6|598005.5|4921439.2|f" | v.in.ascii cat=1 x=2 y=3 out=centers col="cat integer, \
                         east double precision, north double precision, label varchar(43)"

v.db.select centers
v.category centers op=report
# type       count        min        max
# point          6          1          6


#create lines map connecting points to network (on layer 2)
v.net myroads points=centers out=myroads_net op=connect thresh=500
v.category myroads_net op=report
# Layer / table: 1 / myroads_net
# type       count        min        max
# line         837          1          5
#
# Layer: 2
# type       count        min        max
# point          6          1          5

# The network is now prepared.
g.region vect=myroads_net
d.mon x0
d.vect myroads_net
d.vect -c centers icon=basic/triangle
d.font verdana
d.vect centers col=red disp=attr attrcol=label lsize=12

v.net.steiner myroads_net acol=cost tcats=1-6 out=mysteiner
d.vect mysteiner col=blue width=2
v.net.steiner example

SEE ALSO

d.path, v.net, v.net.alloc, v.net.iso, v.net.path, v.net.salesman

AUTHOR

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

Last changed: $Date: 2007-11-11 20:28:29 -0800 (Sun, 11 Nov 2007) $


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