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NAME

       v.net.alloc   -  Allocate  subnets  for nearest centres (direction from
       centre).
       Centre node must be opened (costs >= 0). Costs of centre node are  used
       in calculation

KEYWORDS

       vector, network, allocation

SYNOPSIS

       v.net.alloc
       v.net.alloc help
       v.net.alloc  [-g]  input=name  output=name   [type=string[,string,...]]
       [alayer=integer]           [nlayer=integer]           [afcolumn=string]
       [abcolumn=string]      [ncolumn=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
           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

DESCRIPTION

       v.net.alloc  allocates  subnets  for  nearest  centers  (direction from
       center). center nodes must be opened (costs >=  0).   Costs  of  center
       nodes are used in the calculation.

       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  both  arcs  and nodes, 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.

NOTES

       Nodes and arcs can be closed using cost = -1.

       Center nodes can also be assigned to vector nodes  using  wxGUI  vector
       digitizer.

EXAMPLES

       1. Subnetwork allocation using distance:

       2. Subnetwork allocation using traveling time:

       Example 1: Calculating subnets for 3 center nodes using distances
       # Spearfish
       # center nodes:
       echo "591235.5|4926306.62|1
       596591.8|4917042.5|2
       602722.9|4923544.2|3" | v.in.ascii in=- out=centernodes
       g.copy vect=roads,myroads
       # connect points to network
       v.net myroads points=centernodes out=myroads_net op=connect thresh=200
       # allocate, specifying range of center cats (easier to catch all):
       v.net.alloc myroads_net out=myroads_net_alloc ccats=1-100000 nlayer=2
       # report categories
       v.category myroads_net_alloc option=report
        To display the result, run for example:
       # show result
       g.region vect=myroads_net
       d.mon x0
       d.vect myroads_net layer=1
       #  the  result  has  to  be selected by category number of the relevant
       node:
       d.vect myroads_net_alloc cat=1 col=red layer=1
       d.vect myroads_net_alloc cat=2 col=green layer=1
       d.vect myroads_net_alloc cat=3 col=yellow layer=1
       # center nodes
       d.vect  myroads_net  col=red  icon=basic/triangle  fcol=green   size=12
       layer=2

       Example 2: Calculating subnets for 3 center nodes using traveling time

       # Spearfish
       # center nodes:
       echo "591235.5|4926306.62|1
       596591.8|4917042.5|2
       602722.9|4923544.2|3" | v.in.ascii in=- out=centernodes
       g.copy vect=roads,myroads
       # create lines map connecting points to network
       v.net  myroads points=centernodes out=myroads_net op=connect thresh=500
       alayer=1 nlayer=2
       # set up costs
       # 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,bcost 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:
       # set forward costs
       v.db.update myroads_net_time layer=3 col=cost val="length / speed * 60"
       # set backward costs
       v.db.update myroads_net_time layer=3 col=bcost val="length  /  speed  *
       60"
       # subnetwork allocation with fastest paths
       v.net.alloc    in=myroads_net_time    alayer=3    nlayer=2   afcol=cost
       abcol=bcost out=myroads_net_alloc_time ccats=1-3
        To display the result, run for example:
       # show result
       g.region vect=myroads_net
       d.mon x0
       d.vect myroads_net type=line layer=1
       # the result has to be selected by  category  number  of  the  relevant
       node:
       d.vect myroads_net_alloc_time cat=1 col=red layer=1
       d.vect myroads_net_alloc_time cat=2 col=green layer=1
       d.vect myroads_net_alloc_time cat=3 col=yellow layer=1
       # center nodes
       d.vect  myroads_net_time col=red icon=basic/triangle fcol=green size=12
       type=point layer=2

SEE ALSO

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

AUTHOR

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

       Last changed: $Date: 2013-05-23 13:01:55 -0700 (Thu, 23 May 2013) $

       Full index

       © 2003-2013 GRASS Development Team



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