NAME¶

v.net.salesman - Creates a cycle connecting given nodes (Traveling salesman problem). Note that TSP is NP-hard, heuristic algorithm is used by this module and created cycle may be sub optimal

KEYWORDS¶

vector, network, salesman

SYNOPSIS¶

v.net.salesman v.net.salesman help v.net.salesman [-g] input=name output=name [ type=string[,string,...]] [alayer=integer] [nlayer=integer] [acolumn=string] ccats=range [--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,...]

 

Arc type

 

Options: line,boundary

 

Default: line,boundary

alayer=integer

 

Layer number

 

Arc layer

 

Default: 1

nlayer=integer

 

Layer number

 

Node layer (used for cities)

 

Default: 2

acolumn=string

 

Arcs' cost column (for both directions)

ccats=range

 

Category values

 

Categories of points ('cities') on nodes (layer is specified by nlayer)

DESCRIPTION¶

v.net.salesman calculates the optimal route to visit nodes on a vector network. Costs may be either line lengths, or attributes saved in a database table. These attribute values are taken as costs of whole segments, not as costs to traverse a length unit (e.g. meter) of the segment. For example, if the speed limit is 100 km / h, the cost to traverse a 10 km long road segment must be calculated as length / speed = 10 km / (100 km/h) = 0.1 h. Supported are cost assignments for arcs, and also different costs for both directions of a vector line. For areas, costs will be calculated along boundary lines. The input vector needs to be prepared with v.net operation=connect in order to connect points representing center nodes to the network. Points specified by category must be exactly on network nodes, and the input vector map needs to be prepared with v.net operation=connect.

NOTES¶

Arcs can be closed using cost = -1.

EXAMPLE¶

Traveling salesman for 6 digitized nodes (Spearfish): Shortest path, along unimproved roads: Fastest path, along highways: Searching for the shortest path using distance and the fastest path using traveling time according to the speed limits of different road types: # Spearfish g.copy vect=roads,myroads # we have 6 locations to visit on our trip 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 in=- cat=1 x=2 y=3 out=centers col="cat integer, \
east double precision, north double precision, label varchar(43)" # verify data preparation 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 # find the shortest path v.net.salesman myroads_net ccats=1-6 out=mysalesman_distance # set up costs as traveling time # create unique categories for each road in layer 3 v.category in=myroads_net out=myroads_net_time opt=add cat=1 layer=3 type=line # add new table for layer 3 v.db.addtable myroads_net_time layer=3 col="cat integer,label varchar(43),length double precision,speed double precision,cost double precision" # copy road type to layer 3 v.to.db myroads_net_time layer=3 qlayer=1 opt=query qcolumn=label columns=label # upload road length in miles v.to.db myroads_net_time layer=3 type=line option=length col=length unit=miles # set speed limits in miles / hour v.db.update myroads_net_time layer=3 col=speed val="5.0" v.db.update myroads_net_time layer=3 col=speed val="75.0" where="label='interstate'" v.db.update myroads_net_time layer=3 col=speed val="75.0" where="label='primary highway, hard surface'" v.db.update myroads_net_time layer=3 col=speed val="50.0" where="label='secondary highway, hard surface'" v.db.update myroads_net_time layer=3 col=speed val="25.0" where="label='light-duty road, improved surface'" v.db.update myroads_net_time layer=3 col=speed val="5.0" where="label='unimproved road'" # define traveling costs as traveling time in minutes: v.db.update myroads_net_time layer=3 col=cost val="length / speed * 60" # find the fastest path v.net.salesman myroads_net_time alayer=3 nlayer=2 acol=cost ccats=1-6 out=mysalesman_time To display the result, run for example: # Display the results g.region vect=myroads_net # shortest path d.mon x0 d.vect myroads_net d.vect centers -c icon=basic/triangle d.vect mysalesman_distance col=green width=2 d.font Vera d.vect centers col=red disp=attr attrcol=label lsize=12 # fastest path d.mon x1 d.vect myroads_net d.vect centers -c icon=basic/triangle d.vect mysalesman_time col=green width=2 d.font Vera d.vect centers col=red disp=attr attrcol=label lsize=12

SEE ALSO¶

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

AUTHOR¶

Radim Blazek, ITC-Irst, Trento, Italy Documentation: Markus Neteler, Markus Metz Last changed: $Date: 2013-05-23 22:01:55 +0200 (Thu, 23 May 2013) $ Full index © 2003-2014 GRASS Development Team