Data processing: vehicles – navigation – and relative location – Navigation – Determination of e.t.a.
Reexamination Certificate
1998-07-01
2001-06-26
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Navigation
Determination of e.t.a.
C340S910000, C340S994000, C340S917000, C342S457000, C342S042000, C246S005000, C455S405000
Reexamination Certificate
active
06253148
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to information systems for informing users of public transport networks about waiting times at stops in such networks.
More particularly, the invention relates to an information system for informing users of a public transport network about waiting times for public transport vehicles at stops of the network, the information system comprising:
electronic information devices, each provided with an interface for informing users about waiting times for public transport vehicles, each of said information devices being adapted to determine the waiting times for said public transport vehicles on the basis of successive positions of said public transport vehicles;
a central computer point adapted to broadcast repetitively to the information devices new positions for the public transport vehicles, said broadcasting beginning at successive transmission instants &thgr; and said positions reaching the information devices after a certain average transit time T has elapsed from each broadcast instant &thgr;; and
a locating system adapted to locate the public transport vehicles and to send data to the central computer point representing the position xi(ti) of each public transport vehicle in association with the instant ti at which the vehicle was located.
BACKGROUND OF THE INVENTION
Document WO-A-94/02923 describes an example of such an information system.
The information system described in that document provides satisfaction, but it appears to be desirable to refine the estimates of waiting time as performed by the electronic information devices of the system.
That is the particular object of the present invention.
OBJECTS AND SUMMARY OF THE INVENTION
To this end, according to the invention, in the information system of the kind in question, the central computer point is adapted:
prior to each broadcast instant &thgr;, to estimate the position xi(&thgr;+T) that each public transport vehicle is expected to have at instant &thgr;+T , as a function of the prior positions of the public transport vehicles; and
then, at the broadcast instant &thgr;, to transmit said estimates xi(&thgr;+T) to the information devices as the new positions of the public transport vehicles.
By means of these dispositions, the information devices have data available that faithfully represents the positions of the public transport vehicles at the moment at which said devices receive the data, thereby enabling the information devices to calculate a very accurate estimate of waiting times at stops in the public transport network, and this is achieved while transmitting a minimum volume of data to the information devices.
In particular, it is not necessary to transmit to the information devices the instants ti at which the various public transport vehicles were located.
This provides a saving the time required for data transmission to the information devices, and a saving in occupancy of the transmission network.
In preferred embodiments of the invention, use may optionally be made of one or more of the following dispositions:
at least some of the information devices are portable receiver appliances for receiving one-way radio paging, with the positions of the public transport vehicles being broadcast to said information devices by radio;
the public transport vehicles are buses;
the central computer point is adapted to estimate the position which each public transport vehicle is expected to have at instant &thgr;+T by calculating a distance Li that said vehicle will normally travel between instants ti and &thgr;+T, using the formula:
Li=Vi.(&thgr;+T−ti)
where Vi is an estimated speed for the public transport vehicle, the central computer point being adapted to calculate estimated speeds Vi as a function of earlier positions of the public transport vehicles;
when the most recently known position of said public transport vehicle is not at a stop in the public transport network, the central computer point is adapted to calculate the estimated speed Vi of each public transport vehicle as being an average speed travelled by said public transport vehicle;
when the position of said public transport vehicle as identified by the locating system has been at the same stop for a length of time greater than a predetermined first duration, the central computer point is adapted to calculate the estimated speed Vi of each public transport vehicle as being a past average speed of said public transport vehicle;
when the last known position of the public transport vehicle is for the first time at a stop of the public transport network, the central computer point is adapted to calculate the estimated speed Vi of each public transport vehicle as being equal to zero during a second predetermined duration, followed, after said second predetermined duration has elapsed, by Vi, where Vi is a past average speed of the public transport vehicle in question;
said past average speed is calculated over a period having a duration of less than 1 min;
said past average speed is an average speed calculated over a period of duration less than 5 min, multiplied by a correction factor lying in the range 1.1 to 1.5;
said past speed is the most recent non-zero speed of the public transport vehicle calculated between two successive located positions of said vehicle;
the central computer system is adapted to correct the most recent position xi(ti) of each public transport vehicle on the assumption that said public transport vehicle is at a stop of the public transport network if the most recent position is at a distance from said stop which is less than a certain limit value, which limit value may lie in the range 10 m to 50 m;
the positions of the public transport vehicles at instant &thgr;+T are estimated by the central computer point as a function of at least one parameter other than the data received from the locating system, the central computer point being adapted to compare the positions estimated in this way with the subsequent real positions of the public transport vehicles, and to adjust said parameter as a function of said comparison; and
the central computer point is adapted:
to receive data from at least one of the information devices;
to determine in this way, after each broadcast instant &thgr;, the real instant at which said information device actually receives the positions as broadcast at said broadcast instant; and
to adjust the value of the average transit time T as a function of said real instant of reception.
REFERENCES:
patent: 4791571 (1988-12-01), Takahashi et al.
patent: 5483454 (1996-01-01), Lewiner et al.
patent: 5740046 (1998-04-01), Elestedt
patent: 5970389 (1999-10-01), Lwiner et al.
patent: WO 83/04451 (1983-06-01), None
patent: 2751112 (1996-01-01), None
patent: WO 96/04634 (1996-02-01), None
Decaux Jean-Claude
Le Gars Jacques
Cuchlinski Jr. William A.
Decaux Jean-Claude
Piper Marbury Rudnick & Wolfe
To Tuan C
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