v.net.timetable(1grass) GRASS GIS User's Manual v.net.timetable(1grass)
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 ac-
cess 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 ac-
cess 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 ac-
cess 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 out-
put 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 ar-
rival 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 be-
tween 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 walk-
ing, 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 be-
tween two corresponding points. Finally, instead of straight line seg-
ment, 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 identi-
ficators 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 be-
tween 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
SOURCE CODE
Available at: v.net.timetable source code (history)
Accessed: unknown
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