1v.net.alloc(1)                Grass User's Manual               v.net.alloc(1)
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3
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NAME

6       v.net.alloc  - Allocates subnets for nearest centers.
7       Center  node must be opened (costs >= 0). Costs of center node are used
8       in calculation.
9

KEYWORDS

11       vector, network, cost allocation
12

SYNOPSIS

14       v.net.alloc
15       v.net.alloc --help
16       v.net.alloc  [-tgu]  input=name  output=name    [method=string]    cen‐
17       ter_cats=range       arc_layer=string      arc_type=string[,string,...]
18       node_layer=string     [arc_column=name]      [arc_backward_column=name]
19       [node_column=name]      [turn_layer=string]     [turn_cat_layer=string]
20       [--overwrite]  [--help]  [--verbose]  [--quiet]  [--ui]
21
22   Flags:
23       -t
24           Use turntable
25
26       -g
27           Use geodesic calculation for longitude-latitude locations
28
29       -u
30           Create unique categories and attribute table
31           Default: same category like nearest center
32
33       --overwrite
34           Allow output files to overwrite existing files
35
36       --help
37           Print usage summary
38
39       --verbose
40           Verbose module output
41
42       --quiet
43           Quiet module output
44
45       --ui
46           Force launching GUI dialog
47
48   Parameters:
49       input=name [required]
50           Name of input vector map
51           Or data source for direct OGR access
52
53       output=name [required]
54           Name for output vector map
55
56       method=string
57           Use costs from centers or costs to centers
58           Options: from, to
59           Default: from
60
61       center_cats=range [required]
62           Category values
63           Categories of centers (points on nodes) to which net will be  allo‐
64           cated, layer for this categories is given by nlayer option
65
66       arc_layer=string [required]
67           Arc layer
68           Vector  features can have category values in different layers. This
69           number determines which layer to use. When  used  with  direct  OGR
70           access this is the layer name.
71           Default: 1
72
73       arc_type=string[,string,...] [required]
74           Arc type
75           Input feature type
76           Options: line, boundary
77           Default: line,boundary
78
79       node_layer=string [required]
80           Node layer
81           Vector  features can have category values in different layers. This
82           number determines which layer to use. When  used  with  direct  OGR
83           access this is the layer name.
84           Default: 2
85
86       arc_column=name
87           Arc forward/both direction(s) cost column (number)
88
89       arc_backward_column=name
90           Arc backward direction cost column (number)
91
92       node_column=name
93           Node cost column (number)
94
95       turn_layer=string
96           Layer with turntable
97           Relevant only with -t flag
98           Default: 3
99
100       turn_cat_layer=string
101           Layer with unique categories used in turntable
102           Relevant only with -t flag
103           Default: 4
104

DESCRIPTION

106       v.net.alloc allocates subnets for nearest centers. Center nodes must be
107       opened (costs >= 0). Costs of center nodes are used in the calculation.
108
109       Costs may be either line lengths, or attributes saved in a database ta‐
110       ble.  These  attribute values are taken as costs of whole segments, not
111       as costs to traverse a length unit (e.g. meter)  of  the  segment.  For
112       example, if the speed limit is 100 km / h, the cost to traverse a 10 km
113       long road segment must be calculated as
114       length / speed = 10 km / (100 km/h) = 0.1 h.
115       Supported are cost assignments for both arcs and nodes, and  also  dif‐
116       ferent  costs  for  both directions of a vector line.  For areas, costs
117       will be calculated along boundary lines.
118
119       The input vector needs to be prepared with v.net  operation=connect  in
120       order to connect points representing center nodes to the network.
121
122       The  nearest center can be determined using either costs from the near‐
123       est center or costs to the nearest center with option method. See exam‐
124       ple below.
125
126       By  default,  the category value of the nearest center is used as cate‐
127       gory value for output lines. With the  -u  flag,  output  lines  become
128       unique  categories  and  an  attribute table is created with the fields
129       cat, ocat, center. The ocat field holds the original line  category  in
130       arc_layer and the center field holds the center category in node_layer.
131       Additionally, original  line  categories  are  copied  from  the  input
132       arc_layer to layer 2 in the output, together with any attribute table.
133
134       Application  of flag -t enables a turntable support. This flag requires
135       additional parameters turn_layer and turn_cat_layer that are  otherwise
136       ignored.  The  turntable  allows to model e.g. traffic code, where some
137       turns may be prohibited. This means that the input layer is expanded by
138       turntable  with  costs  of  every  possible  turn  on any possible node
139       (intersection) in both directions.  Turntable can  be  created  by  the
140       v.net  module.  For  more information about turns in the vector network
141       analyses see wiki page.
142

NOTES

144       Nodes and arcs can be closed using cost = -1.
145
146       Center nodes can also be assigned to vector nodes  using  wxGUI  vector
147       digitizer.
148

EXAMPLES

150       1. Subnetwork allocation using distance:
151
152       2. Subnetwork allocation using traveling time:
153
154       Example 1: Calculating subnets for 3 center nodes using distances
155       # Spearfish
156       # center nodes:
157       echo "591235.5|4926306.62|1
158       596591.8|4917042.5|2
159       602722.9|4923544.2|3" | v.in.ascii in=- out=centernodes
160       g.copy vect=roads,myroads
161       # connect points to network
162       v.net myroads points=centernodes out=myroads_net op=connect thresh=200
163       # allocate, specifying range of center cats (easier to catch all):
164       v.net.alloc myroads_net out=myroads_net_alloc center_cats=1-100000 node_layer=2
165       # report categories
166       v.category myroads_net_alloc option=report
167       To display the result, run for example:
168       # show result
169       g.region vector=myroads_net
170       d.mon x0
171       d.vect myroads_net layer=1
172       # the result has to be selected by category number of the relevant node:
173       d.vect myroads_net_alloc cat=1 col=red layer=1
174       d.vect myroads_net_alloc cat=2 col=green layer=1
175       d.vect myroads_net_alloc cat=3 col=yellow layer=1
176       # center nodes
177       d.vect myroads_net col=red icon=basic/triangle fcol=green size=12 layer=2
178
179       Example 2: Calculating subnets for 3 center nodes using traveling time
180       # Spearfish
181       # center nodes:
182       echo "591235.5|4926306.62|1
183       596591.8|4917042.5|2
184       602722.9|4923544.2|3" | v.in.ascii in=- out=centernodes
185       g.copy vect=roads,myroads
186       # create lines map connecting points to network
187       v.net myroads points=centernodes out=myroads_net op=connect thresh=500 arc_layer=1 node_layer=2
188       # set up costs
189       # create unique categories for each road in layer 3
190       v.category in=myroads_net out=myroads_net_time opt=add cat=1 layer=3 type=line
191       # add new table for layer 3
192       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"
193       # copy road type to layer 3
194       v.to.db myroads_net_time layer=3 qlayer=1 opt=query qcolumn=label columns=label
195       # upload road length in miles
196       v.to.db myroads_net_time layer=3 type=line option=length col=length unit=miles
197       # set speed limits in miles / hour
198       v.db.update myroads_net_time layer=3 col=speed val="5.0"
199       v.db.update myroads_net_time layer=3 col=speed val="75.0" where="label=’interstate’"
200       v.db.update myroads_net_time layer=3 col=speed val="75.0" where="label=’primary highway, hard surface’"
201       v.db.update myroads_net_time layer=3 col=speed val="50.0" where="label=’secondary highway, hard surface’"
202       v.db.update myroads_net_time layer=3 col=speed val="25.0" where="label=’light-duty road, improved surface’"
203       v.db.update myroads_net_time layer=3 col=speed val="5.0" where="label=’unimproved road’"
204       # define traveling costs as traveling time in minutes:
205       # set forward costs
206       v.db.update myroads_net_time layer=3 col=cost val="length / speed * 60"
207       # set backward costs
208       v.db.update myroads_net_time layer=3 col=bcost val="length / speed * 60"
209       # subnetwork allocation with fastest paths
210       v.net.alloc in=myroads_net_time arc_layer=3 node_layer=2 arc_column=cost arc_backward_column=bcost out=myroads_net_alloc_time center_cats=1-3
211       To display the result, run for example:
212       # show result
213       g.region vector=myroads_net
214       d.mon x0
215       d.vect myroads_net type=line layer=1
216       # the result has to be selected by category number of the relevant node:
217       d.vect myroads_net_alloc_time cat=1 col=red layer=1
218       d.vect myroads_net_alloc_time cat=2 col=green layer=1
219       d.vect myroads_net_alloc_time cat=3 col=yellow layer=1
220       # center nodes
221       d.vect myroads_net_time col=red icon=basic/triangle fcol=green size=12 type=point layer=2
222
223       Example 3: Differences between costs from centers and costs to centers
224       Each lane of the two-lane road is a one-way road.
225
226       1. Subnetwork allocation from centers:
227
228       A center reaches any point following the one-way lanes.
229
230       2. Subnetwork allocation to centers:
231
232       Any  node  reaches  reaches  the  nearest  center following the one-way
233       lanes.
234
235       In case of an accident, the ambulance  should  come  from  the  nearest
236       ’from’ hospital and go to the nearest ’to’ hospital.
237       # North Carolina
238       # center nodes are hospitals:
239       # connect hospitals to streets as layer 2
240       v.net input=streets_wake points=hospitals output=streets_hospitals operation=connect thresh=400 arc_layer=1 node_layer=2
241       v.to.db map=streets_hospitals layer=1 type=line option=cat columns=cat
242       # close oneway roads
243       v.db.update map=streets_hospitals column=TF_COST value=-1 where="ONE_WAY = ’FT’"
244       v.db.update map=streets_hospitals column=FT_COST value=-1 where="ONE_WAY = ’TF’"
245       # add costs to newly created lines
246       v.db.update map=streets_hospitals column=TF_COST value=0 where="cat > 49746"
247       v.db.update map=streets_hospitals column=FT_COST value=0 where="cat > 49746"
248       # from centers
249       v.net.alloc in=streets_hospitals out=streets_hospitals_alloc_from center_cats=1-10000 arc_column=FT_COST arc_backward_column=TF_COST
250       # to centers
251       v.net.alloc in=streets_hospitals out=streets_hospitals_alloc_to method=to center_cats=1-10000 arc_column=FT_COST arc_backward_column=TF_COST
252

SEE ALSO

254       d.path, v.net, v.net.iso, v.net.path, v.net.steiner, v.net.salesman
255

AUTHOR

257       Radim Blazek, ITC-Irst, Trento, Italy
258       Documentation: Markus Neteler, Markus Metz
259
260   TURNS SUPPORT
261       The  turns  support  was  implemnented  as part of GRASS GIS turns cost
262       project at  Czech  Technical  University  in  Prague,  Czech  Republic.
263       Eliska  Kyzlikova, Stepan Turek, Lukas Bocan and Viera Bejdova partici‐
264       pated at the  project.   Implementation:  Stepan  Turek  Documentation:
265       Lukas Bocan Mentor: Martin Landa
266

SOURCE CODE

268       Available at: v.net.alloc source code (history)
269
270       Main  index  | Vector index | Topics index | Keywords index | Graphical
271       index | Full index
272
273       © 2003-2019 GRASS Development Team, GRASS GIS 7.8.2 Reference Manual
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277GRASS 7.8.2                                                     v.net.alloc(1)
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