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v.net.iso(1)		    GRASS GIS User's Manual		  v.net.iso(1)

NAME
       v.net.iso  - Splits subnets for nearest centers by cost isolines.
       Splits net to bands between cost	isolines (direction from center). Cen-
       ter 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]	  cen-
       ter_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=nameA [required]
	   Name	of input vector	map
	   Or data source for direct OGR access

       output=nameA [required]
	   Name	for output vector map

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

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

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

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

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

       node_layer=stringA [required]
	   Node	layer
	   Vector  features can	have category values in	different layers. This
	   number determines which layer to use. When used with	direct OGR ac-
	   cess	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 ta-
       ble. 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 dif-
       ferent 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	 near-
       est 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 (in-
       tersection) 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  partici-
       pated  at  the  project.	  Implementation:  Stepan Turek	Documentation:
       Lukas Bocan Mentor: Martin Landa

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

       Main index | Vector index | Topics index	| Keywords index  |  Graphical
       index | Full index

       A(C) 2003-2020 GRASS Development	Team, GRASS GIS	7.8.3 Reference	Manual

GRASS 7.8.3							  v.net.iso(1)

NAME | KEYWORDS | SYNOPSIS | DESCRIPTION | NOTES | EXAMPLES | SEE ALSO | AUTHOR | SOURCE CODE

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