NAME¶
v.net.distance - Computes shortest distance via the network
between the given sets of features.
Finds the shortest paths from a feature 'to' to every feature 'from' and various
information about this realtion are uploaded to the attribute table.
KEYWORDS¶
vector, network, shortest path
SYNOPSIS¶
v.net.distance
v.net.distance help
v.net.distance [-
g]
input=
name
output=
name [
from_layer=
integer]
[
from_cats=
range] [
from_where=
sql_query]
[
to_layer=
integer] [
to_cats=
range]
[
to_where=
sql_query]
[
to_type=
string[,
string,...]]
afcolumn=
name
[
abcolumn=
name] [--
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
- from_layer=integer
-
From layer number or name
A single vector map can be connected to multiple database tables. This
number determines which table to use.
Default: 1
- from_cats=range
-
From category values
Example: 1,3,7-9,13
- from_where=sql_query
-
From WHERE conditions of SQL statement without 'where' keyword
Example: income = 10000
- to_layer=integer
-
Layer number
To layer number or name
Default: 1
- to_cats=range
-
To category values
Example: 1,3,7-9,13
- to_where=sql_query
-
To WHERE conditions of SQL statement without 'where' keyword
Example: income = 10000
- to_type=string[,string,...]
-
To feature type
Options: point,line,boundary
Default: point
- afcolumn=name
-
Arc forward/both direction(s) cost column
- abcolumn=name
-
Arc backward direction cost column
DESCRIPTION¶
v.net.distance finds the nearast element from set
to for every
element in set
from.
NOTES¶
These two sets are given by the respective
layer,
where and
cats parameters. The type of
to features is specified by
to_type parameter and all
from features are
points. A
table is linked to
output map containing various information about the
relation. More specifically, the table has three columns:
cat,
tcat and
dist storing category of each
from feature,
category of the nearest
to feature and the distance between them
respectively. Furthemore,
output map contains the shorest path between
each
cat,
tcat pair. Each path consist of several lines. If a
line is on the shorest path from a point then the category of this point is
assigned to the line. Note that every line may contain more than one category
value since single line may be on the shortest path for more than one
from feature. And so the shortest paths can be easily obtained by
querying lines with corresponding category number.
The costs of arcs in forward and backward direction are specified by
afcolumn and
abcolumn columns respectively. If
abcolumn
is not given, the same cost is used in both directions.
EXAMPLES¶
Find shortest path and distance from every school to the nearest hospital and
show path from school number one.
v.net.distance input=city output=nearest from_where="type=school"
to_where="type=hospital" afcolumn=SHAPE_LEN
d.vect nearest cats=1
SEE ALSO¶
v.net.path, v.net.allpairs, v.net.distance,
v.net.alloc
AUTHORS¶
Daniel Bundala, Google Summer of Code 2009, Student
Wolf Bergenheim, Mentor
Last changed: $Date: 2011-11-08 10:42:51 +0100 (Tue, 08 Nov 2011) $
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