FR2693820A1 - Traffic data acquisition for work in progress - estimating vehicle position in urban area and systematically correcting positions on map by measurement at different positions - Google Patents

Abstract

The acquisition of data is determined by use of a signal from the estimated position (71,73) of a vehicle (1) to a small uncertainty and on a map of urban traffic routes (40). A signal is generated from the front of the vehicle with a signal for the speed and of the position with a value of uncertainty. There is an area of uncertainty (70) on the map for the estimated position (71,73). From the signal at the front it can be determined if there is a branch (51,57) on the route map inside the area of uncertainty and where the vehicle is to be formed. Using a set of data of the urban traffic it can be determined on which branch, speed and direction the traffic is moving. The signal for the speed is for a period of time inside the area that is received as the approximate position of the vehicle and by using further signals it is possible to reduce the area of uncertainty and determine the route, position and speed of the vehicles. USE - Determination of direction, position and speed of vehicles on urban route.

Description

Method of acquiring data on urban traffic,
central and vehicle for implementing the process
The present invention relates firstly to a method
acquisition of data on "urban" traffic in
from signals representative of the estimated position
a vehicle, known to an uncertainty, and a
traffic lane plan of an urban area where
find the vehicle.

A process of this kind is already known, in which a
navigation system, of the inertial central type,
installed in the vehicle, supplied by radio to a
centralization of data on ciculation
urban, at regular time intervals, the distance to
flight of birds traveled by the vehicle from its point
of departure, as well as the direction in which it
moved relative to this one. If he knows with
the position of the vehicle's starting point, the
central can then locate it on the map and, starting from
this urban position, report for each direction
provided by the inertial unit, the distance
corresponding.

If the vehicle has thus transmitted its position to
sufficiently close time intervals, the
successive positions are close enough to
define, on the plan, a line of points passing through
all the routes successively taken by the
vehicle and defining its route.

In addition, if the central office realizes that one of the points of the
path is not exactly on a lane but on the edge
of it, he can conclude that the system of
navigation is imprecise and provides slightly false indications; he corrects them by moving the point concerned to place it as closely as possible on the plane track. The reports on the map of the following positions are systematically corrected by the value of the correction made, until a new correction has to be made again, necessitated by the loss of precision of the navigation system over time.

The above method allows the central, from the sequence of positions thus determined and by memorizing the times at which they are noted, to divide the distance actually traveled between two positions, determined by calculating the length of the path on the plan, by the time taken to cover it, to provide an estimated average speed for a journey along the route followed. We can then inform by radio all the motorists of a city crossed by one or more vehicles of assistance to circulation.

However, it is necessary to have, on board each vehicle, a precise system making it possible to determine the absolute position of the carrier vehicle in the form of terrestrial coordinates, which, plotted on the plan, provides a relative position relative to the tracks of the plan and which must correspond exactly to the lane on which the vehicle is located. However, a system of the inertial central type is very expensive and fragile, which is a constraint for the driver. As indicated above, the errors of an inaccurate inertial unit can be remedied, but at the cost of frequent readjustment calculations throughout the journey. It is then necessary, in the vehicle, to calculate and transmit very often information indicating the route followed. , so that the central can move an erroneous position by transferring it to the nearest channel, which supposes that the positions are transmitted often enough so that the inertial unit has not drifted too much between two successive instants of position determination. However, the correction of the error may only be apparent, if the nearest channel was not the right one. Frequent transmissions require means of calculating and managing this information and lead to the transmission of longer radio messages, therefore more costly, and cluttering the available radio channels.

In addition, the information relating to speed is only very rough since it is only an average value on a journey including several lanes, a value which can be influenced by traffic congestion on part of the journey and does not finely translate the fluidity of traffic on a given lane.

The navigation system mentioned above can be replaced by a radio receiver receiving beacon messages allowing it to determine its position. For example, the GPS system (Global Positioning System) is a navigation system comprising a plurality of satellites which transmit radio signals allowing a receiver to determine its position in longitude and latitude with known good accuracy, which is however not still sufficient to resolve an ambiguity in the position of the car between two neighboring lanes. In addition, the reception of radio waves from GPS satellites is, in cities, subject to the vagaries of propagation due to tall buildings.

The present invention aims to overcome these drawbacks.

To this end, the invention relates to a method of acquiring data on urban traffic from a signal representative of the estimated position of a vehicle, known to within an uncertainty, and from a plan of the traffic lanes. of an urban area where the vehicle is located, characterized in that - a heading signal representative of the heading is generated
tracked by the vehicle as it passes by said
estimated position, - a speed signal representative of
vehicle speed during an interval of
time determined before passing through said
estimated position, - by means of the position signal and the value of
uncertainty, we position an area on the plane
of uncertainty around the estimated position, - by means of the heading signal, at least one
section of track of the plan extending in the area
of uncertainty and on which the
vehicle and - we associate, in a group of data on the
urban traffic, said section, said speed
and a direction of flow corresponding to said heading.

Thus, it is possible to have, on board the vehicle, only inexpensive position determination means.

The exact position of the vehicle is located on the portions of lanes extending inside the area of uncertainty and the lanes, whose direction is incompatible with the heading signal, are not retained, which very often allows remove ambiguities between channels.

We then know a precise urban position, with which is associated a speed corresponding to a known direction of traffic. A multiplicity of data of this kind, obtained by means of one or more vehicles, makes it possible to have a fairly precise overview of traffic conditions and, in particular, to locate congestion.

Said group of data can be inhibited when, at the end of the process, more than one section is determined, in order to retain only reliable data.

Due to the large number of positions that can be determined, the absence of data from time to time represents only a small loss of information.

The invention also relates, for the implementation of the method of the invention, to a data acquisition center on urban traffic, comprising memory means containing a plan of the traffic lanes of an urban area where there is a vehicle, as well as receiving means arranged to receive a position signal representative, to an uncertainty known to the central office, of the estimated geographical position of the vehicle, characterized in that said receiving means are arranged to receive a heading signal and a speed signal respectively representative of the heading of the vehicle on passing through said position and of its average speed during a determined time interval before passing through said position, and
that it includes calculation means arranged for
receive said receiving signals from receiving means
position and heading, to determine, from
the value of said uncertainty and in cooperation
with said memory means, at least one section of
plane path extending into an area of uncertainty
surrounding said position, section on which can be
find the vehicle, the central being arranged to
receive, from receiving means, said signal
speed, to associate, in a group of data on
urban traffic, said section, said speed
and a direction of flow corresponding to said heading.

Finally, the invention also relates to a vehicle
comprising means arranged to determine, at a
known uncertainty, its geographic position and
transmitting means for transmitting a signal
representative of said position, characterized by the
fact that it includes calculation means arranged
for, from received signals representative of the heading
instantaneous and instantaneous vehicle speed,
generate a heading signal representative of the heading followed
by the vehicle just before passing through said
geographic position and a speed signal
representative of the vehicle speed during a
time interval determined before passing through
said geographic position and to order
the transmission, by said transmitting means, of said
position, heading and speed signals.

The invention will be better understood with the aid of the following description of a preferred embodiment of the method of the invention, with reference to the appended drawing, in which - FIG. 1 is a block diagram illustrating the
process of the invention - Figure 2 shows an example of a plan on which are
carried over from positions of a car
performs the above process and - Figure 3 is a diagram illustrating the position
temporal of time intervals during which
the course and speed of the car are measured.

The method of the invention is implemented by means of a car 1 comprising a GPS receiver 2, a magnetometer 10 and an odometer 12 connected at output to inputs of a signal processing circuit 17 connected to the input of a microprocessor 4 controlling a radio transmitter 8. The circuit 17 filters signals which it receives before transmitting them to the microprocessor 4. The microprocessor 4 is arranged to cyclically control the transmission, by the transmitter 8, on a channel radio 16, with a position and heading signal 15 representing the geographic position, latitude and longitude, of car 1 and its heading at the time of signal 15 emission. In FIG. 3, T1 and T2 represent two successive instants of emission of signal 15, delimiting a cycle of emission of signal 15, corresponding respectively to two successive estimated positions 71 and 73 (FIG. 2) of the car 1. A memory 6, associated with the microprocessor 4, contains data 7 which are it cyclically provided by the microprocessor 4 and which represent the latitude and longitude of the last position transmitted, in the form of a signal 15, by the transmitter 8. The microprocessor 4 can also, by the same means, command, at the end of each above cycles, the emission, on channel 16, of a speed signal 21, generated as explained below, representing the speed of car 1 over a predetermined time interval tm (FIG. 3) ending, here, at the time of sending the signal 15, like the instant T2. In this example, the signals 15 and 21 are sent in grouped form in the same message on the radio channel 16.

The radio channel 16 connects the transmitter 8 to a central 20 for acquiring data on urban traffic.

Although the process is not limited to "urban" traffic, it is however of major interest in urban areas, where, compared to the countryside, traffic conditions are often more difficult and the lanes are closer, which may cause ambiguity in determining the position of the car 1.

The exchange 20 includes a radio receiver 18 tuned to receive signals on channel 16 and connected at output to a computer 24 which has two calculation blocks, 22 and 34, as well as two memories 26 and 30. The memory 26 contains data representing the value of an uncertainty affecting any position determined by the car 1 and supplies to the calculation block 22, on request thereof, an uncertainty signal 27 representative of the value of the above uncertainty.

The memory 30 contains a map 32 consisting of an electronic description of the lane positions of a given geographical area 40, here urban, traveled by the car 1. At the request of the calculation block 22, the memory 30 supplies the calculation block 34 a signal 31 representing vectors giving the urban position and the direction of tracks of an area of uncertainty, located in the urban area 40, surrounding a position transmitted by the car 1.

Similarly, the memory 30 supplies the calculation block 34 with a traffic direction signal 33 indicating the direction or directions of traffic authorized on the tracks in the area of uncertainty. Thus, for each lane, the signal 33 corresponds to one or two vectors, representing the direction or the two directions of circulation, while the signal 31 corresponds to a segment of the same position as the corresponding vector (s) and does not provide any indication traffic direction.

The process is carried out as follows.

The signal processing circuit 17 receives from the GPS receiver 2, when the latter is in connection with GPS satellites, data contained in a signal 3 representative of the geographical position of the car 1.

The circuit 17 also receives, continuously, an instantaneous heading signal 13, coming from the magnetometer 10, and an instantaneous speed signal 14, coming from the odometer 12. The microprocessor 4, thus having the various successive heading tracks followed and the travel distance corresponding to each, depending on the speed, then determines, over time, the deviation of the successive geographic positions occupied by the car 1 compared to the last position transmitted to the central 20.

When the microprocessor 4 must, at the instant T2, command the transmission, to the central 20, of the position of the car 1, it receives beforehand, from the memory 6, the data 7, from which it calculates the position car 1 instantaneous by shifting the last position, transmitted at time T1, by an amount equal to the deviation determined above. A position signal 5 is supplied by the microprocessor 4 to the radio transmitter 8.

Whether or not the heading signal 13 is used to calculate the position of the car 1, it is in all cases used by the microprocessor 4 to calculate, at each cycle, a heading signal 9 representing an average heading followed by the car 1 on a short time interval tc, here just before sending the position signal 5, at time T2.

The microprocessor 4 simultaneously transmits the position 5 and heading 9 signals to the transmitter 8 which transmits them, in the form of signal 15, to the receiver 18. The latter transmits the corresponding data, in the form of a signal 25 , in calculation block 22.

The memory 26 of the computer 24 supplies to the calculation block 22, at its request, the uncertainty signal 27. the calculation block 22 defines, according to the signals 25 and 27, the urban position occupied by an area of uncertainty 70, limited by a circle 76 represented in FIG. 2, centered on the estimated urban position 71, provided by the car 1 and of radius equal to the value of the uncertainty of position. The actual position of car 1 is therefore inside the area of uncertainty 70.

The calculation block 22 transmits to the memory 30 a signal 23 representing the geographical position of the area of uncertainty 70 and the memory 30 supplies in return, to the calculation block 34, the signal 31.

If a straight line carrying a "vector" (signal 31) representing the position of a channel intersects the circle 76 and if the "vector" considered is at least partially in the circle 76, the calculation block 34 then determines, for each of the "vectors" above, by comparison between the signals 23 and 31, one or more sections of tracks, here 51 and 57, of the area of uncertainty 70 whose direction corresponds, with a tolerance, to the course provided by car 1. In the case where, as here, several track sections are thus determined, the traffic direction signal 33 is supplied by the memory 30 to the calculation block 34 which then eliminates the sections whose direction of traffic is incompatible with the heading of car 1 provided by signal 23.

In the present example, the course followed by the car 1 is assumed to be substantially opposite to the one-way traffic on the section 51, represented by an arrow 53, so that only the section 57 is retained by the calculation block 34, which provides a signal 91 representing the position of the section 57.

In the case where there are still at least two sections of track on which the car 1 can be, it is not, in this example, provided any information on this subject and the output of the signal 91, provided in principle at each transmission estimated position, is inhibited.

The supply of signal 91 would certainly be possible, since the determination of at least two sections would clearly show that the corresponding information is not secure. The invention saves the user from having to reject uncertain information.

Of course, if no section is in the area of uncertainty 70, no signal 91 is provided: the position is wrong and rejected.

In order to improve the accuracy of determining the urban position of the car 1, there is provided, in this example, a GPS receiver 42 of known position, here fixed and close to that of the central 20, periodically supplying the calculation block 22 a signal 43 representative of the geographical position of the receiver
GPS 42.

The computer 24, which stores the value of the precise geographical position of the GPS receiver 42, compares it to that provided by the signal 43, giving the geographical position of the GPS receiver 42. The geographical position of the GPS receiver 42 being known with precision, the computer 24 thus determines the error due to the satellites and therefore corrects the geographical position provided by the car 1. The computer 24 then defines the urban position of an area of uncertainty (not shown) of size smaller than the initial area 70, which serves, in place of the latter, for determining the sections exposed above and makes it possible to achieve, by its reduced size, less ambiguity between sections.

Furthermore, the odometer 12 supplying, to the microprocessor 4, the signal 14 representative of the value of the instantaneous speed of the car 1, the corresponding information is integrated by the latter over a predetermined interval tm ending, here, at the instant T2 of transmission of the position 73 of the car 1 associated with an area of uncertainty 78.

The above integration provides the value of the average speed during the time interval tm, which is, at time T2, sent by the microprocessor 4 to the calculation block 34, in the form of a signal 11 arriving to the transmitter 8, which then transmits the speed signal 21. The latter is received by the receiver 18 and transmitted to the calculation block 22 in the form of a signal 41, itself transmitted to the calculation block 34 by means of the signal 23.

The calculation block 34, which has in memory the value of the predetermined time interval tm, can then fix with precision, at the diameter near the area of uncertainty 78, the position of a segment 83, on the track corresponding to position 73, to which the above average speed is associated, since the segment 83 ends at the location where position 73 is reported. The position of segment 83, determined by means of signal 91 generated at time T2 , as well as the value of the associated average speed and the corresponding direction of movement are supplied at the output of the calculation block 34 in the form of a signal 93. When the output of the signal 91 is inhibited, the same is true of the signal 93 .

It will be understood that the measurement of the average speed can be related to a predetermined distance traveled, and not to a time interval, such as tm.

Having, for each of the urban positions of car 1, the position information, heading and speed indicated above, the operating center 20, under the control of an operator, can then send messages by radio intended to inform all motorists in urban area 40 on traffic conditions for the lanes traveled, in the specified direction, by car 1.

In the description above, it has been assumed, for the sake of clarity, that the position signal 5 was sent immediately as soon as the microprocessor 4 had generated it. It will be understood that the position signal 5 as well as all those emitted by the car 1 can be memorized and emitted in deferred time if the channel 16 is not always available.

Claims (7)

1. Method for acquiring traffic data  urban from a signal (5) representative of the  estimated position (71, 73) of a known vehicle (1)  to an uncertainty (27) near, and of a plane (32) of  traffic lanes in an urban area (40) where  find the vehicle (1),  characterized by the fact that  - a heading signal (9) representative of the  heading followed by the vehicle (1) as it passes by  said estimated position (71, 73),  - a speed signal is generated (21)  representative of vehicle speed (1)  during a specified time interval (tm)  before passing through said estimated position (71,  73),  - by means of the position signal (5) and the value  of uncertainty (27), we position on the plane  (32) an area of uncertainty (70) around the  estimated position (71, 73),  - by means of the heading signal (9), it is determined at  minus a section (51, 57) of track of the plane (32)  lying in the area of uncertainty (70) and on  which vehicle can be found (1) and  - we associate, in a group of data (93) on the  urban traffic, said section (51, 57),  said speed (21) and a direction of circulation  corresponding to said heading (9). 2. Method according to claim 1, in which  inhibits said data group (93) when more  of a section (51, 57) are determined. 3. Central (20) data acquisition on the  urban traffic, including memory means  (30) containing a plan (32) of the traffic lanes  an urban area (40) where a vehicle is located  (1), as well as receiving means (18) agencies  to receive a position signal (15)  representative, to an uncertainty (27) near known to the  central (20), estimated geographic position  (71, 73) of the vehicle (1), characterized by the fact  that said receiving means are arranged to  receive a heading signal and a speed signal  respectively representative of the heading of the vehicle to  its passage through said position and its speed  average over a specified time interval  before it passes through said position, and that it  comprises calculation means (24) arranged for  receiving said receiving means (18)  position and heading signals (15), to  determine, from the value of said  uncertainty (27) and in cooperation with them  memory means (30), at least one section (51, 57)  plan track (32) extending in an area  of uncertainty (70) surrounding said position,  section, on which the vehicle can be (1),  the central being arranged to receive, means  receivers (18), said speed signal, for  associate, in a data group (93) on the  urban traffic, said section (51, 57), said  speed (21) and a corresponding traffic direction  audit cap (9). 4. Central (20) according to claim 3, wherein  said calculation means (24) are arranged for  inhibit said data group (93) when more  of a section (51, 57) are determined. 5. Central (20) according to one of claims 3 and 4,  wherein said calculating means (24) are  arranged to receive, memory means (30), a  traffic direction signal authorized on  said channels and to determine from among said  sections of tracks, those (93) whose direction of  traffic is compatible with said traffic signals  position and heading (15). 6. Central (20) according to one of claims 3 to 5,  wherein said calculating means (24) are  arranged to receive from a receiver  GPS (42), with a known position with precision,  information (43) representative of the position  said GPS receiver (42), to calculate one  correction to be made to any position (71, 73) of the  vehicle (1) determined by the latter by means of  GPS satellites. 7. Vehicle comprising means (2, 4) arranged for  determine, to an uncertainty (27) known, its  geographic position (71, 73) and means  transmitters (8) for transmitting a signal (5)  representative of said position (71, 73),  characterized by the fact that it includes means for  calculation (4) arranged for, from received signals  representative of the instant heading (13) and the  instantaneous speed (14) of the vehicle (1), generate  a heading signal (9) representative of the heading followed by  the vehicle (1) just before passing through said  geographic position (71, 73) and a signal  speed (11) representative of the vehicle speed  (1) during a determined time interval (tm)  before passing through said geographic position  and for controlling the transmission, by said transmitting means (8), of said position (5), heading (9) and speed (11) signals.