Method of automatically determining the position of vehicles

Details Method of automatically determining the position of vehicles Method of automatically determining the position of vehicles

1998-11-24

2001-02-27

Blum, Theodore M. (Department: 3614)

Communications: directive radio wave systems and devices (e.g.,

Directive

Including a satellite

C701S215000

Reexamination Certificate

active

06195038

ABSTRACT:

TECHNICAL FIELD
The invention is directed to a method of automatically determining the position of vehicles by means of a DGPS (
D
ifferential
G
lobal
P
ositioning
S
ystem) wherein at least one vehicle in the ÖPNV (
L
ocal
P
ublic
P
assenger
T
raffic) and a fixed station (
2
) receive GPS (
G
lobal
P
ositioning
S
ystems) data, which characterize the distance to GPS satellites, where the GPS data from the fixed station are transmitted as correction data via service radio transmissions to the mobile stations in the vehicles, and wherein the transmission of the correction data takes place through expansion of the service radio transmissions by at least one information byte.
BACKGROUND OF THE INVENTION
From the technical article “AVLS—A system for automatically determining the position of vehicles” by A. Bethmann et al., 1994, Alcatel SEL, Stuttgart, it is known to use a number of position determination possibilities to compute the exact location of vehicles. The GPS Global Positioning System is used to that end for example. The system comprises 25 satellites, not all of which are still active however. The accuracy of the location is approximately 100 meters for private users. The determination of the position is based on the direct distance measurement between satellites and vehicular receiver by means of the half-wave time delay measurement method with synchronized time reference. Inaccuracies must be expected, because ionospheric disturbances affect the signal propagation time, and atmospheric disturbances and damping limit the availability of the signal. Multipath reception furthermore causes positioning errors, particularly in a city environment. Signal shading is possible in tunnels.
The problems with the global positioning system are partly avoided when a differential method is used. A GPS receiver is installed in a known reference location. This reference receiver is able to determine very accurately the distance from its location to the satellites. In the vehicles these distances are now compared with the distances measured in the vehicles. This determines the errors in the distance measurement and thereby improves the result of the measurement. With this method the positioning accuracy can be increased to 10 meters in the horizontal direction. The above-cited technical article also discusses the type of data transmission between the fixed station and the mobile devices. The use of (PMR=
P
rivate
M
obile
R
adio) service radio for communication by the mobile stations with the fixed station is discussed as an example of a solution. Service radio networks are widely used, particularly in local public traffic, but their data capacity cannot be expanded to any desired extent.
SUMMARY OF THE INVENTION
Therefore the object exists to integrate the advantages of the differential position determination GPS into existing motor pools by using existing service radio networks for exchanging the relevant data.
The method of the invention is a method of automatically determining the position of vehicles by means of a DGPS method (
D
ifferential
G
lobal
P
ositioning
S
ystem), whereby at least one vehicle in the ÖPNV (
L
ocal
P
ublic
P
assenger
T
raffic) and a fixed station receive GPS (
G
lobal
P
ositioning
S
ystems) data, which characterize the distance to GPS satellites, where the GPS data from the fixed station are transmitted as correction data via service radio transminssions to the mobile stations in the vehicles, and wherein the transmission of the correction data takes place through expansion of the service radio transmissions by at least one information byte. This method has the advantage that by including the GPS data of the fixed station in a service radio telegram, the correction data needed to compute an accurate position are transmitted to the mobile station. The system to carry out the method requires no replacement of the already existing infrastructure and no change in the provided service radio protocols. The relevant correction data are redirected inside of individual information bytes to the mobile station in the vehicle.
It is particularly advantageous that the method can be built without great expense into the quasi norm 420 of the VDV (Association of German Traffic Entrepreneurs).
It is furthermore possible to insert in a simple manner up to 15 additional information bytes into the data frame of the structure provided by the VDV protocol. It is an advantage that an information byte is transmitted by signalling whether correction data are sent by a satellite, and if so by one or by two satellites. In addition, the entire information required to correct the position, such as alignment rates, times, scale factors etc., is transmitted in the information bytes.


REFERENCES:
patent: 5689431 (1997-11-01), Rudow et al.
“Automatic Vehicle Location System” Electrical Communication, 2 Quartal, 1994, Paris France by Bethmann et al, pp. 129-135.
“Differential GPS Markets in the 1990's” by Lewis. Proceedings of Electro International, Jun. 21, 1995, IEEE, New York, US. pp. 163-186.
“AVLS—A System for Automatically Determinign the Position of Vehicles” by A. Bethmann et al. 1994 Alcatel SEL. Stuttgart, pp. 129-135.

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