Provided by: grass-doc_7.0.3-1build1_all 
NAME
v.net.timetable - Finds shortest path using timetables.
KEYWORDS
vector, network, shortest path
SYNOPSIS
v.net.timetable
v.net.timetable --help
v.net.timetable input=name [layer=string] output=name [arc_layer=string]
[node_layer=string] [arc_column=string] [arc_backward_column=string]
[node_column=string] [walk_layer=string] route_id=name stop_time=name to_stop=name
walk_length=name [--overwrite] [--help] [--verbose] [--quiet] [--ui]
Flags:
--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=name [required]
Name of input vector map
Or data source for direct OGR access
layer=string
Layer number or name
Vector features can have category values in different layers. This number determines
which layer to use. When used with direct OGR access this is the layer name.
Default: 1
output=name [required]
Name for output vector map
arc_layer=string
Arc layer
Vector features can have category values in different layers. This number determines
which layer to use. When used with direct OGR access this is the layer name.
Default: 1
node_layer=string
Node layer
Vector features can have category values in different layers. This number determines
which layer to use. When used with direct OGR access this is the layer name.
Default: 2
arc_column=string
Arc forward/both direction(s) cost column (number)
arc_backward_column=string
Arc backward direction cost column (number)
node_column=string
Node cost column (number)
walk_layer=string
Layer number or name with walking connections or -1
A single vector map can be connected to multiple database tables. This number
determines which table to use. When used with direct OGR access this is the layer
name.
Default: -1
route_id=name [required]
Name of column with route ids
Default: route_id
stop_time=name [required]
Name of column with stop timestamps
Default: stop_time
to_stop=name [required]
Name of column with stop ids
Default: to_stop
walk_length=name [required]
Name of column with walk lengths
Default: length
DESCRIPTION
v.net.timetable finds the shortest path between two points using timetables.
v.net.timetable reads input, one query per line, from the standard input and writes output
to the standard output as well as to the output map and to tables linked to layers 1 and
2. Each line of input must follow one of the following formats:
PATH_ID FROM_X FROM_Y TO_X TO_Y START_TIME MIN_CHANGE MAX_CHANGES WALK_CHANGE
PATH_ID FROM_STOP TO_STOP START_TIME MIN_CHANGE MAX_CHANGES WALK_CHANGE
where PATH_ID is the identificator of a query that is used in the output map to
differentiate between queries. Search begins at START_TIME. MIN_CHANGE gives the minimum
number of time (inclusively) for a change from one route to another. MAX_CHANGES denotes
the maximum number of changes allowed or -1 if infinity. WALK_CHANGE is 1 or 0 depending
whether walking from a stop to another stop is considered a change or not. Finally, the
path is found from FROM_STOP to TO_STOP in latter case and from the stop closest to
(FROM_X, FROM_Y) coordinates to the stop closest to (TO_X, TO_Y) coordinates in former
case.
For each input query, module outputs a description of the shortest path to the standard
output. For example, using the tables given below, for the following input:
47 130 300 0 1 5 0
the following output is produced:
Route 15, from 130 leaving at 15 arriving to 250 at 22
Walk from 250 leaving at 22 arriving to 300 at 24
Moreover, the module writes the path to the output map and stores all the information
necessary to reconstruct the path to the tables. Table corresponding to stops/points is
linked to layer 1 and looks, after the query, as follows:
cat|path_id|stop_id|index|arr_time|dep_time
1|47|130|1|0|15
2|47|250|2|22|22
3|47|300|3|24|24
where CAT is the category of a point in the map, PATH_ID is the path identificator,
STOP_ID is the identificator of the stop as used in the input map, INDEX is the index of
the stop on the path (i.e, index=1 is the first stop visited, ...) and ARR_TIME and
DEP_TIME denote the arrival time and departure time respectively. Arrival time for the
first stop on the path is always equal to START_TIME and departure time for the last stop
is always equal to the arrival time.
The table linked to the second layer corresponds to subroutes taken between stops. The
following table is obtainedd for the above query:
cat|path_id|from_id|to_id|route_id|index|from_time|to_time
1|47|130|250|15|1|15|22
2|47|250|300|-1|2|22|24
where CAT is the category of lines of subroute between stops FROM_ID to TO_ID, ROUTE_ID is
the identificator of the route taken or -1 if walking, INDEX and PATH_ID are as above and
FROM_TIME and TO_TIME denote the times between which the route is taken.
The output map contains the points on the positions of used stops. If a subroute is taken
between two stops then a line segment is added between two corresponding points. Finally,
instead of straight line segment, the actual paths of routes can be given in paths layer.
If this parameter is used then each line in the input map must contain identificators as
category numbers of all routes passing through the line. The module then finds the path
between two stops and writes this path instead. In case of walking from one stop to
another, straight line between the stops is used.
NOTES
Timetables are stored in a table linked to the given layer of the input map. Timetable
consists of routes and each route is just a sequence of stops with specified arrival
times. If two sequences of stops differ only in times then they still correspond to two
routes. For example, if there is a bus line that leaves every 20 minutes and follow
exactly the same path every time then there still needs to be a separate route for every
time. For each stop (given by the category number of the point) the table storing
information about the routes must contain the list of all routes stopping at the
stop(given by route identificators) together with arrival times. That is, the table must
contain three columns: stop - which is the key of the table, route_id and stop_time where
each triple corresponds to a route arriving to a stop and a certain time. For example, a
valid table might look as follows:
cat|route_id|stop_time
100|5|0
130|5|10
150|5|20
250|5|30
300|5|40
260|15|5
130|15|15
250|15|22
150|35|17
250|35|27
300|35|37
100|35|50
Note that stop_time is an integer and so you can use any units and offest to specify
arrival times.
Also, walking connections between stops can be given by a table linked to walking layer of
the input map. If this parameter is -1 then walking between stops is not allowed. The
table must contain three columns: stop - which is the key of the table, to_stop and
length. A record in the table says that it takes length
units of time to walk from stop to to_stop. The following is a valid table:
cat|length|to_stop
250|2|300
Beware that this only means that it is possible to walk from stop 250 to stop 300 but not
the other way round.
EXAMPLES
To find a path from stop with identificator 130 to stop with category 300, starting at
time 0, with one time unit for change, maximum of 5 changes and with walking not
considered a change of route, we use the following command:
echo "47 130 300 0 1 5 0" | v.net.timetable \
input=buses output=path layer=5 walking=6 path=7
If, on the other hand, we know the coordinates of the places then the following command
might be used:
echo "47 10.31 54.31 90.21 28.21 0 1 5 0" | v.net.timetable \
input=buses output=path layer=5 walking=6 path=7
SEE ALSO
v.net, v.net.path, v.net.distance
AUTHORS
Daniel Bundala, Google Summer of Code 2009, Student
Wolf Bergenheim, Mentor
Last changed: $Date: 2013-05-23 21:59:24 +0200 (Thu, 23 May 2013) $
Main index | Vector index | Topics index | Keywords index | Full index
© 2003-2016 GRASS Development Team, GRASS GIS 7.0.3 Reference Manual