table of contents
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 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 offset 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: Thursday Aug 01 05:16:52 2024
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