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NAME

       v.net.iso  - Splits subnets for nearest centers by cost isolines.
       Splits  net  to  bands  between cost isolines (direction from center). Center node must be
       opened (costs >= 0). Costs of center node are used in calculation.

KEYWORDS

       vector, network, cost allocation, isolines

SYNOPSIS

       v.net.iso
       v.net.iso --help
       v.net.iso    [-tgu]    input=name    output=name     [method=string]     center_cats=range
       costs=integer[,integer,...]          arc_layer=string         arc_type=string[,string,...]
       node_layer=string   [arc_column=name]    [arc_backward_column=name]     [node_column=name]
       [turn_layer=string]     [turn_cat_layer=string]     [--overwrite]   [--help]   [--verbose]
       [--quiet]  [--ui]

   Flags:
       -t
           Use turntable

       -g
           Use geodesic calculation for longitude-latitude locations

       -u
           Create unique categories and attribute table
           Default: one category for each iso-band

       --overwrite
           Allow output files to overwrite existing files

       --help
           Print usage summary

       --verbose
           Verbose module output

       --quiet
           Quiet module output

       --ui
           Force launching GUI dialog

   Parameters:
       input=name [required]
           Name of input vector map
           Or data source for direct OGR access

       output=name [required]
           Name for output vector map

       method=string
           Use costs from centers or costs to centers
           Options: from, to
           Default: from

       center_cats=range [required]
           Category values
           Categories of centers (points on nodes) to which net will be allocated, layer for this
           categories is given by nlayer option

       costs=integer[,integer,...] [required]
           Costs for isolines

       arc_layer=string [required]
           Arc layer
           Vector  features  can have category values in different layers. This number determines
           which layer to use. When used with direct OGR access this is the layer name.
           Default: 1

       arc_type=string[,string,...] [required]
           Arc type
           Input feature type
           Options: line, boundary
           Default: line,boundary

       node_layer=string [required]
           Node layer
           Vector features can have category values in different layers. This  number  determines
           which layer to use. When used with direct OGR access this is the layer name.
           Default: 2

       arc_column=name
           Arc forward/both direction(s) cost column (number)

       arc_backward_column=name
           Arc backward direction cost column (number)

       node_column=name
           Node cost column (number)

       turn_layer=string
           Layer with turntable
           Relevant only with -t flag
           Default: 3

       turn_cat_layer=string
           Layer with unique categories used in turntable
           Relevant only with -t flag
           Default: 4

DESCRIPTION

       v.net.iso splits a network into bands between cost isolines (distance from center). Center
       nodes must be opened (costs >= 0). The 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.

       The  nearest  center can be determined using either costs from the nearest center or costs
       to the nearest center with option method.

       By default, the iso band number is used as category value for output lines.  With  the  -u
       flag,  output  lines  become  unique categories and an attribute table is created with the
       fields cat, ocat, center, isonr, isolbl. The ocat field holds the original  line  category
       in  arc_layer,  the  center field holds the center category in node_layer, the isonr field
       holds the  iso  band  number  and  the  isolbl  field  holds  a  label  for  the  isoband.
       Additionally,  original  line categories are copied from the input arc_layer to layer 2 in
       the output, together with any attribute table.

       Application of flag  -t  enables  a  turntable  support.  This  flag  requires  additional
       parameters  turn_layer and turn_cat_layer that are otherwise ignored. The turntable allows
       to model e.g. traffic code, where some turns may be prohibited. This means that the  input
       layer  is  expanded  by  turntable  with costs of every possible turn on any possible node
       (intersection) in both directions.  Turntable can be created by the v.net module. For more
       information about turns in the vector network analyses see wiki page.

NOTES

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

       Nodes must be on the isolines.

EXAMPLES

       The  map  must  contain  at  least  one  center (point) on the vector network which can be
       patched into with v.net.

       Isonetwork using distance:

       Isonetwork using time:

   Subdivision of a network using distance:
       # Spearfish
       # start node:
       echo "591280.5|4926396.0|1" | v.in.ascii in=- out=startnode
       g.copy vect=roads,myroads
       # connect point to network
       v.net myroads points=startnode out=myroads_net op=connect thresh=200
       # define iso networks using distance:
       v.net.iso input=myroads_net output=myroads_net_iso center_cats=1-100000 costs=1000,2000,5000
       The network is divided into 4 categories:
       v.category myroads_net_iso option=report
       # ... reports 4 categories:
       #cat | distance from point in meters
       #1          0 - < 1000
       #2       1000 - < 2000
       #3       2000 - < 5000
       #4             >= 5000
       To display the result, run for example:
       g.region n=4928200 s=4922300 w=589200 e=596500
       d.mon x0
       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

   Subdivision of a network using traveling time:
       Prepare the network as above:
       # Spearfish
       # start node:
       echo "591280.5|4926396.0|1" | v.in.ascii in=- out=startnode
       g.copy vect=roads,myroads
       # connect point to network
       v.net myroads points=startnode out=myroads_net op=connect thresh=200
       Define costs as traveling time dependent on speed limits:
       # 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"
       # define iso networks using traveling time:
       v.net.iso input=myroads_net_time output=myroads_net_iso_time arc_layer=3 node_layer=2 arc_column=cost arc_backward_column=bcost center_cats=1-100000 costs=1,2,5
       To display the result, run for example:
       # add table with labels and coloring
       v.db.addtable myroads_net_iso_time columns="cat integer,trav_time varchar(20),GRASSRGB varchar(11)"
       # labels
       v.db.update map=myroads_net_iso_time layer=1 column=trav_time value="0 - 1" where="cat = 1"
       v.db.update map=myroads_net_iso_time layer=1 column=trav_time value="1 - 2" where="cat = 2"
       v.db.update map=myroads_net_iso_time layer=1 column=trav_time value="2 - 5" where="cat = 3"
       v.db.update map=myroads_net_iso_time layer=1 column=trav_time value="> 5" where="cat = 4"
       # colors
       # cats=1: blue
       v.db.update map=myroads_net_iso_time layer=1 column=GRASSRGB value="000:000:255" where="cat = 1"
       # cats=2: green
       v.db.update map=myroads_net_iso_time layer=1 column=GRASSRGB value="000:255:000" where="cat = 2"
       # cats=3: orange
       v.db.update map=myroads_net_iso_time layer=1 column=GRASSRGB value="255:128:000" where="cat = 3"
       # cats=4: magenta
       v.db.update map=myroads_net_iso_time layer=1 column=GRASSRGB value="255:000:255" where="cat = 4"
       # show results
       g.region n=4928200 s=4922300 w=589200 e=596500
       d.mon x0
       d.vect myroads_net_iso_time layer=1 -a rgb_col=GRASSRGB
       d.vect myroads_net col=red icon=basic/triangle fcol=green size=12 layer=2

SEE ALSO

        d.path, v.net, v.net.alloc, v.net.path, v.net.salesman, v.net.steiner, v.patch

AUTHOR

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

   TURNS SUPPORT
       The turns support was implemnented as part of  GRASS  GIS  turns  cost  project  at  Czech
       Technical  University  in  Prague,  Czech Republic.  Eliska Kyzlikova, Stepan Turek, Lukas
       Bocan and Viera  Bejdova  participated  at  the  project.   Implementation:  Stepan  Turek
       Documentation: Lukas Bocan Mentor: Martin Landa

       Last changed: $Date: 2017-06-23 08:55:26 +0200 (Fri, 23 Jun 2017) $

SOURCE CODE

       Available at: v.net.iso source code (history)

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