v.net.steiner(1)

NAME
v.net.steiner

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

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: 2007-11-12 05:28:29 +0100 (Mon, 12 Nov 2007) $

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