METHOD AND APPARATUS FOR DETERMINATION OF POSITION

Abstract: It is disclosed a method and apparatus for determination of position of a moving object on the basis of a selection and storing a current position (Px) as a waypoint (Wx) if the following criteria are fulfilled: (1) the current distance (Dx) of the position (Px) along the road from the previous waypoint (Wx-1) is greater than a first parameter X; OR (2a) the current distance (Dx) of the position (Px) along the road from the previous waypoint (Wx-1) is greater than a second parameter Y, wherein Y < X, AND (2b) the deviation (Ax) between the current travelling direction of the object and the direction established by the connection of the last two waypoints (Wx-1, Wx-2) is greater than a third parameter Z, AND (2c) the speed of the object is greater than a minimum speed S. The stored waypoints allow a determination of the travelling direction which is advantageous for localization of vehicles driving on parallel one-way lanes.

Description: Method and apparatus for determination of position The invention relates to a method and apparatus for determination of position of a moving object like a vehicle, airplane, ship, especially along a predetermined way (route) . Navigation systems for determination of position by means of the GPS (Global Positioning System) are well known not only for application in airplanes and ships but have an increasing importance also for localization of a vehicle position. This purpose requires receiver and evaluation units of compact size and reasonable costs. Further, for reducing communication times and communication costs, the data are condensed as much as possible, however, this is limited by the fact that the data have to be significant enough for determination of the vehicle position with sufficient accuracy. WO 95/13594 discloses a device for recording information about a vehicle's itinerary. The device comprises a receiver for receiving position data of the vehicle and a memory device for continuously storing of position data, data on times of positions and data which identify the driver of the vehicle on an easy replaceable data carrier. WO 00/34932 discloses a monitoring system for automatically tracking the positions of a fleet of mobile units. Each mobile unit carries a position determining means, a processing means and a transmitting means for sending the latest position of the mobile unit to a central control unit at certain intervalls. For reducing the required transmission capacity, the processing means stores a number of rules for determining the interval between transmission of position update messages to the central control unit. These rules are based upon various factors like the direction of travel of the mobile unit, its location or distance from predetermined and stored other locations or a predetermined line defining the route or the required positional accuracy or other predetermined conditions or events. WO 00/10027 discloses a position monitoring method and apparatus for mobile units in which these units transmit current position data to a central control unit periodically or each time the unit has moved a predetermined distance. The positions are displayed on an electronic map in a variety of selectable ways. US-PS 5,598,167 discloses a method and apparatus for determining an actual position of a vehicle and for recurrently and wirelessly transmitting the same to a remote station. For restricting the number of transmissions a discrete internal change of status (e.g. a predetermined travelled distance) is detected in the vehicle and transmission is effected upon detection of such a status. It is an object of the invention to provide a method and apparatus for determination of position of a moving object which is very simple to implement and which requires only minor expense of hardware equipment. It is another object of the invention to provide a method and apparatus for determination of position of a moving vehicle which allows an exact determination of its position even with respect to two parallel one-way lanes on a highway. It is another object of the invention to provide a simple method and apparatus for selecting position data of a moving object as waypoints to be stored and displayed, so that a reduced number of waypoints describe a travelled route with better accuracy and reduced error especially in case of very different curved and straight courses as well as different velocities of the object. These and other objects are solved by a method according to claim 1 and an apparatus according to claim 8. By this, the decision about storing a position data as a (new) waypoint is made on the basis and in dependence of previously stored waypoints and not on every previous position data. Using (only) the waypoints for indicating and / or displaying the travelled route, a higher accuracy of the description of the travelled route with a reduced data volume is achieved. The subclaims are directed to advantageous embodiments of the solutions according to claim 1 and 8, respectively. Further details, features and advantages become apparent from the following description of a preferred embodiment of the invention with reference to the drawings, in which shows: Fig. 1 a schematic diagram of the environment of a method and apparatus according to the invention; Fig. 2 a schematic block diagram of an apparatus according to the invention; Fig. 3 a schematic view for explaining selection of waypoints; and Fig. 4 a chart of a route of travel of a vehicle in which selected waypoints are indicated. A preferred environment of an inventive method and apparatus is shown in Figure 1. It comprises a customer service center 10 with an operator 11. At least one vehicle 20, at least one boat or ship 24, as well as one or more stationary equipments 25 like a remote facility or plant communicate with the service center 10 via a cellular communication network 30 like GSM (european standard) or AMPS (US standard) and / or a satellite communication network 31, both for exchanging of information, data and voice communication, each in both directions. Even software programs can be transmitted if necessary. Emergency assistance vehicles 22 and a roadside assistance vehicle 23 communicate with the service center 10 in a similar manner or in any other way and are activated by the service center in case of need by one of the objects 20, 24, 25. A position of each object can be detected by means of a global positioning system (GPS) 40. Vehicles, especially trucks, which are guided or monitored by the service center, are equipped with appropriate transmitting means for transmitting position data to the service center. In case of accident or emergency, if an assistance vehicle 23 is needed, the driver of the same must exactly know the actual position of the vehicle which is calling for help, especially if such vehicle was driving on a highway or road with separated lanes for each direction. The indication of the position by means of GPS is normally not good enough to allow a distinction between two parallel one-way lanes (one for each direction) and an indication on which lane the target car was travelling. The method and apparatus according to the invention allows such distinction and indication by determining not only the position but also the direction of movement of the object. This is achieved on the basis of a series of certain previously localized positions which are selected under certain criteria and stored in a corresponding memory as waypoints and which are transmitted if necessary to the service center or an assistance car, so that an actual position of the object as well as its route of travel prior to that position and consequently its moving direction can be determined which allows a decision on which lane the target object actually is. The position of the object is determined for example every second in a known manner by evaluating GPS signals. However, for saving memory and reducing processor demands, communication costs and communication times, only selected position data are stored in a memory and transmitted if necessary as waypoints along the travelled route. The transmission of position data can either be automatically initiated in case of an accident, it can be initiated from the service center or it can be manually initiated at the object by e.g. operating a switch. Figure 2 shows schematically an apparatus according to the invention. It comprises a first means 100 for determining a current position P of the object which is preferably a GPS receiving and evaluating unit. The position data are supplied to a data processing unit 200. This unit 200 comprises a second, third and fourth means . The second means 110 is a memory for storing previous positions which have been determined as waypoints. The third means 120 is provided for determining a current distance D of the object from a previous waypoint W and for determining a current deviation A between a current travelling direction and a previous travelling direction of the object. The previous direction is preferably established by the connection of the last two stored waypoints. Further, the third means 120 is preferably provided for determining the current speed of the object. The fourth means 130 is provided for comparing the current distance D and the current deviation A with at least one set of parameters X, Y, Z, which define criteria for storing a position as a new waypoint, and, if the criteria are fullfilled, for actually storing the current position P in the second means 110 (memory) as a new waypoint W. Preferably, the fourth means 130 is also provided for comparing the current speed with a predetermined minimum speed S and for storing the current position P as a new waypoint W if, as an additional prerequisite, the current speed is above the minimum speed S. Preferably, more than one limit speed LI, L2, .. and more than one set of parameters (XI, Yl, Zl) , (X2, Y2, Z2),...is provided. In this case, the fourth means 130 is preferably provided for comparing the current speed with the at least one limit speed LI; L2;.. and for applying one of the sets of parameters (XI, Yl, Zl) ; (X2, Y2, Z2);... in dependence of which of the limit speeds (LI; L2;..) the current speed of the object is below or above. Finally, a transmitting means 140 is provided for transmitting said stored waypoints to a remote station for indicating and / or displaying the position and / or the travelling direction of the object. The selection of waypoints shall be described with reference to Figure 3. The continuous line indicates the travelled route of the object, the point P is the current position of the object. The point W0 and Wl is a first and a second waypoint, respectively. D denotes the current distance along the road between the second (last) waypoint Wl and the actual position P, whereas X and Y are parameters indicating a predetermined value of distance from the last waypoint which is the second waypoint Wl in Figure 3, and A is a deviation between the current travelling direction of the object and the direction established by the connection of the last two waypoints WO and Wl. In the following description, a value which is "currently" determined shall be denoted with an index "x", whereas such value which has been determined before the current value shall be denoted with an index "x-1" and so on. First, a current position Px and a current distance Dx of the object from a previous position Px-1 which has been stored as a waypoint Wx-1 is determined. Then, a current deviation Ax between a current travelling direction and a previous travelling direction of the object is determined. The previous travelling direction is preferably according to Figure 3 the direction of the line which connects the last two stored waypoints WO (generally Wx-2) and Wl (generally Wx-1) . The criteria for selecting and storing a current position Px as a new waypoint Wx are as follows: (1) The current distance Dx of the position Px along the road from the previous waypoint Wx-1 is greater than a first parameter X; OR (2) (a) The current distance Dx of the position Px along the road from the previous waypoint Wx-1 is greater than a second parameter Y, wherein Y < X, AND (b) the deviation Ax between the current and previous travelling directions of the object is greater than a third parameter Z, AND (c) the speed of the object is greater than a minimum speed which is a fourth parameter S. If one of the conditions (1) or (2a-c) is fulfilled, then the current position Px of the object is stored as a new waypoint Wx. Preferably, the last seven waypoints are stored in the memory and are used for displaying the travelled route of the object. Criterium (1) makes sure that waypoints are taken at least at a certain interval even while travelling on a road which is substantially straight. Criterium (2a) maintains a smaller distance between waypoints if according to criterium (2b) a highway turns or a road in a city has corners and roundabouts. The speed S according to criterium (2c) is a lower speed limit to make sure that while travelling very slow, for example in parking areas, waypoints are not taken even if the other criteria (2a) and (2b) are fulfilled. However, the criterium (2c) is optional and can be deleted if the route does not lead through such areas in which speed has to be very low. In the example of Figure 3, the current position P is marked and stored as a new waypoint, if the speed of the object is above the minimum speed S and if its distance D from the second waypoint Wl is greater than Y and if the deviation angle A is bigger than Z degrees. If one or more of these criteria have still not been fulfilled, when the object reaches the distance X from the second waypoint Wl, a new waypoint is taken anyway. The current speed of the object and its distance D as well as the deviation angle A are evaluated on the basis of GPS data and compared according to the above criteria and stored by means of an evaluation unit comprising a memory unit inside the obj ect . The parameters (X, Y, Z) are predetermined in dependence of the speed of the object in comparison to a limit speed L. In case of a vehicle which is normally driving in a city or on highways with common speed ranges, one limit speed L is sufficient. The limit speed L is chosen to distinguish between city traffic and traffic on highways so that an appropriate value could be about 50 km/h. Consequently, a first set of parameters (XI, Yl, Zl) for speeds below the limit speed L and a second set of parameters (X2, Y2, Z2) for speeds above the limit speed L is fixed. Various testing with numerous different routes has revealed preferred values for the first set of parameters as of (500m, 50m, 45°) and for the second set of parameters as of (1000m, 100m, 45°) . The minimum speed S was set to 5 km/h. Although the angle deviation Z was set to be 45° in both speed ranges, the value for Z should ideally be predetermined somewhat minor in the speed range above the limit speed L and somewhat larger in the speed range below the limit speed L especially because in cities, many turns are full 90° street corners. However, 45° seems at present to be a fairly good compromise for both speed ranges. However, more than one speed limit Ll; L2;... and accordingly more than two sets of parameters (XI, Yl, Zl) ; (X2, Y2, Z2) ; ... can be predetermined and applied wherein the current speed is compared with those limit speeds . Preferably, the last seven waypoints are stored in the memory and transmitted to a remote station (service center) if necessary. At the service center, the waypoints are transferred into a road map or indicated on a display showing an electronic map. The latest waypoint shows the latest position of the car, whereas the order of all waypoints indicates the travelling direction so that the position of the car even with respect to two parallel one-way lanes on a road or highway can be localized. Figure 4 is a schematic illustration of a map, indicated at a remote station, with a road 10 running through a city 11 and the surrounded countryside 12. A vehicle 13 travels along the road. The previous positions of the vehicle which have been selected as waypoints according to the invention are each indicated with a cross. The last seven waypoints W0 to W6 are stored in the memory of the evaluation unit inside the vehicle. These waypoints may be transmitted to e.g. the service center at a predetermined event. This event may be an accident which is detected with an appropriate sensor in the vehicle. It is also possible for the service center to transmitt a special signal to the vehicle that will enable the vehicle to transmit the waypoints. The transmission of waypoints can also be manually initiated by e.g. operating a switch in the vehicle. Figure 4 shows how several waypoints are grouped at narrower turns in the city and how the distance between waypoints increases with speed as the trip goes out to the countryside on a more straight way. The steps of the inventive method are preferably written as a computer program code which is stored in and run on a data processing unit like a computer.

Claims: Claims 1. Method for determination of position of a moving object, comprising the following steps: determining a current distance (Dx) ■ of the object from a previous position (Px-1) which has been stored as a waypoint (Wx-1) ; determining a current deviation (Ax) between a current travelling direction and a previous travelling direction which is evaluated on the basis of at least one previous waypoint; comparing the current distance (Dx) and the current deviation (Ax) with at least one set of parameters (X, Y, Z) which define criteria for storing a position as a new waypoint; determining and storing the current position (Px) as a new waypoint (Wx) if the criteria are fullfilled; and repeating the above steps and storing a predetermined number of last waypoints (Wx, Wx-1, Wx-2,...) for indicating position and / or travelling direction of the object. 2. Method according to claim 1, characterized in that the criteria are defined as fullfilled if: (1) the current distance (Dx) is greater than the first parameter (X) ; OR (2a) the current distance (Dx) is greater than the second parameter (Y) wherein Y < X; AND (2b) the deviation (Ax) between the current travelling direction and the direction established by the connection of the last two waypoints (Wx-1, Wx-2) is greater than the third parameter (Z) . 3. Method according to claim 2, characterized in that the criteria are defined as fullfilled if in AND-combination with condition (2b) : (2c) the speed of the object is greater than a predetermined minimum speed S . 4. Method according to claim 1, comprising the following steps: determining the current speed of the object and comparing the current speed with at least one limit speed (Ll; L2; .. ) ; applying one of a plurality of predetermined sets of parameters [(XI, Yl, Zl) ; (X2, Y2, Z2);...] in dependence of which of the limit speeds (Ll; L2;..) the current speed of the object is below or above. 5. Method according to one of claims 1 to 4, comprising the following step: transmitting the predetermined number of last waypoints (Wx, Wx-1, Wx-2,...) at a predetermined event. 6. Computer program comprising computer program code means adapted to perform a method according to one of claims 1 to 4 when said program is run on a computer. 7. Computer program product stored on a computer usable medium, comprising computer program code means to perform a method according to one of claims 1 to 4 when loaded into the internal memory of a computer. 8. Apparatus for determination of position of a moving object, comprising: a first means (100) for determining a current position (Px) of the object; a second means (110) for storing previous positions (Px-1, Px-2,...) of the object as waypoints (Wx-1, Wx- Λ , ... ) ; a third means (120) for determining a current distance (Dx) of the object from a previous waypoint (Wx-1) and for determining a current deviation (Ax) between a current travelling direction and a previous travelling direction of the object; and a fourth means (130) for comparing the current distance (Dx) and the current deviation (Ax) with at least one set * of parameters (X, Y, Z) , which define criteria for storing a position as a new waypoint, and, if the criteria are fullfilled, for storing the current position (Px) in the second means (110) as a new waypoint (Wx) . 9. Apparatus according to claim 8, characterized in that the third means (120) is provided for additionally determining the current speed of the object, and the fourth means (130) is provided for additionally comparing the current speed with a predetermined minimum speed (S) and for storing the current position (Px) as a new waypoint (Wx) if, as an additional prerequisite, the current speed is above the minimum speed (S) . 10. Apparatus according to claim 9, characterized in that the fourth means (130) is provided for comparing the current speed with at least one limit speed (Ll; L2;..) and for applying one of a plurality of predetermined sets of parameters [(XI, Yl, Zl) ; (X2, Y2, Z2);...] in dependence of which of the limit speeds (Ll; L2;..) the current speed of the object is below or above. 11. Apparatus according to one of claims 8 to 10, characterized in a transmitting means (140) for transmitting said stored waypoints (Wx-1, Wx-2,...) to a remote station for indicating and / or displaying the position and / or the travelling direction of the object. 12. Apparatus according to one of claims 8 to 11, characterized in that the first means (100) is a GPS receiver, and the second to fourth means (110 to 130) are implemented in a data processing unit (200) comprising a memory and a computer program code means for performing the method according to one of claims 1 to 4 when run on the data processing unit (200) .

Inventors: GUDMUNDSSON STEFAN, JONSSON SVEN, GUDMUNDSSON, STEFAN, JONSSON, SVEN
Applicants: GUDMUNDSSON STEFAN, JONSSON SVEN, VOLVO TEKNISK UTVECKLING AB, GUDMUNDSSON, STEFAN, JONSSON, SVEN
Application year: 2001
Main classification: G01S5
IPC codes: G01C21, G01S5