NAME
v.net.path - Find shortest path on vector network. Reads start/end pointsfrom standard input in 2 possible formats:
id start_point_category end_point_category
id start_point_x start_point_y end_point_x end_point_y
Points specified by category must be exactly on network nodes.
SYNOPSIS
v.net.path
v.net.path help
v.net.path [-gs] input=string output=string [type=string[,string,...]] [afield=integer] [nfield=integer] [afcol=string] [abcol=string] [ncol=string] [maxdist=float]
Flags:
- -g
- Use geodesic calculation for longitude-latitude locations
- -s
- Write output as original input segments, not each path as one line.
Parameters:
- input=string
- Name of input vector
- output=string
- Name of output vector
- type=string
- Arc type
- Options: line,boundary
- Default: line,boundary
- afield=integer
- Arc field
- Default: 1
- nfield=integer
- Node field
- Default: 2
- afcol=string
- Arc forward/both direction(s) cost column
- abcol=string
- Arc backward direction cost column
- ncol=string
- Node cost column
- maxdist=float
- Maximum distance to the network if start/end are given as coordinates. If start/end point is outside this threshold, the path is not found and error message is printed. To speed up the process, keep this value as low as possible.
- Default: 1000
DESCRIPTION
v.net.path can find shortest path(s) on the vector network.
Costs may be either line lengths, or attributes saved in a database
table. These attributes values are taken as costs of whole segments. If read
from the table, arcs' costs may be different in both directions.
Shortest paths are written to output vector file and attached attribute table.
NOTE
If the columns 'afcol', 'abcol' and 'ncol' costs are not
specified, the length of network segments is measured and
zero costs are assumed for nodes.
When using attributes, the length of segments is not used. To get
more precise results, length should be taken indirectly into account
by attributes. For example, to get the fastest path the columns
'max_speed' and 'length' are required. The correct fastest path can then
be found by specifying afcol=length/max_speed (pg driver). If needed,
the line length can be calculated and written to the attributes table
by v.to.db.
SEE ALSO
d.path,
v.net,
v.net.alloc,
v.net.iso,
v.net.salesman,
v.net.steiner,
v.to.db
AUTHOR
Radim Blazek, ITC-Irst, Trento, Italy
Last changed: $Date: 2004/03/09 08:29:38 $
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