Ubuntu Manpage: v.net.distance - Computes shortest distance via the network between the given sets of features.

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 nearest element in set to for every point 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. 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 a
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.

v.net.distance will not work if you are trying to find the nearest neighbors within a group of nodes,
i.e. where to and from are the same set of nodes, as the closest node will be the node itself and the
result will be zero-length paths. In order to find nearest neighbors within a group of nodes, you can
either loop through each node as to and all other nodes as from or create a complete distance matrix with
v.net.allpairs and select the lowest non-zero distance for each node.

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

AUTHORS

       Daniel Bundala, Google Summer of Code 2009, Student
       Wolf Bergenheim, Mentor

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

       Full index

       © 2003-2013 GRASS Development Team

GRASS 6.4.3                                                                               v.net.distance(1grass)