GB2255250A - Location determining arrangement - Google Patents

Abstract

A vehicle location determining arrangement includes a module 6 carried by the vehicle 5, a plurality of receiver stations 1, 2 and 3 and a base station 4. If the driver of the vehicle wishes to summon assistance, he operates the module 6 causing an identification code to be transmitted. The time of receipt of the transmitter signal at each of the receiver stations 1, 2 and 3 is recorded and transmitted to the base station 4. The position of the vehicle 5 can then be determined and appropriate assistance dispatched. The arrangement may also be used for other circumstances for example, for locating the position of a pedestrian. <IMAGE>

Description

LOCATION DETERMINING ARRANGEMENT This invention relates to an arrangement for determining the location of a person or object and more particularly to obtaining information regarding the position at a remote base station.

If a vehicle breaks down, for example, unless the driver possess a car phone or other form of transmitter, he must leave the vehicle in order to summon assistance. The driver may be concerned about the possibility of being attacked when leaving the vehicle, particularly if it has broken down in a remote location or on a motorway.

The present invention arose from the consideration of this problem but it is believed that it also has other applications.

According to the invention there is provided an arrangement for determining the location of an object or person comprising: a transmitter adapted to be carried by said object or person, a plurality of receiver stations for receiving signals transmitted by the said transmitter, a base station and means for determining the relative times of reception of a signal transmitted by said transmitter at-the receiver stations.

As the positions of the receiver stations are known, by monitoring the time of reception of a signal transmitted by the transmitter, the distance travelled by the signal may be determined and hence the location of the object or person. Thus, if equipment in accordance with the invention is carried on a vehicle, say, for summoning assistance in the case of a breakdown, the driver is able to request help without needing to leave his vehicle. As his position may be determined without the intervention of the driver, a breakdown service or other rescue organisation which monitors the signals-received at the base station may obtain accurate positional information even when the driver is unsure of his location.

When the signal is transmitted at a number of times and the object or person is moving, the positional information may be derived when only two receiver stations are available. However, to avoid ambiguity, it is preferred that the arrangement of receiver stations is such that at least three are within the transmitter range of any mobile carrying a transmitter. If the position may be determined at more than one time, the direction of movement may also be determined.

The base station may also act as a receiver station or may be a separate dedicated installation remote from the receiver stations. As the arrangement does not rely on signal strength in making the location determination, only a few receiver stations are capable of covering a relatively large region. This ensures that costs incurred in setting up the installation are minimised.

Although it is envisaged that the invention would be particularly applicable in case of summoning assistance to the occupants of vehicles, it may also be advantageously used for people involved in other activities, such as mountain walking or jogging.

Some ways in which the invention may be performed are now described by way of example with the reference to the accompanying drawings in which: Figure 1 schematically illustrates an arrangement in accordance with the invention; Figures 2 and 3 show parts of the arrangement of Figure 1 in greater detail; and Figure 4 schematically illustrates an alternative to the part shown in Figure 3.

With reference to Figure 1, a vehicle location arrangement includes a plurality of similar receiver stations 1, 2 and 3, only some of which are shown, distributed over a region covered by the arrangement and a base station 4. A vehicle 5 travelling through the region is equipped with a module 6 by means of which a driver may summon assistance should he break down, for example. If he requires help, the driver activates the module 6 to transmit identification signals via an antenna 7 mounted on the vehicle. The signals are received by the receive stations 1, 2 and 3 and their relative times of reception monitored.

By utilising this information, the position of the vehicle 5 may be determined, as is explained in greater detail below.

The module 6 is shown in greater detail in Figure 2.

In this embodiment of the invention, the module 6 includes three buttons, 8, 9 and 10 which can be activated to transmit information defining the type of assistance required. One button 8 is used to request assistance from a vehicle breakdown and recovery organisation, another button 9 is employed to summon medical assistance and the third button 10 requests attendance by the fire service. When-a button is depressed, an appropriate code is transmitted from an associated store 11, 12 and 13 to a combiner 14. On receipt of a signal from one of the stores 11, 12 and 13, the combiner 14 accesses an identification (ID) code from store a 15. This ID code is specific to the vehicle equipped with the module 6 or to the driver and, may represent the driver's membership number of a breakdown service.The combined signal is transmitted along a line 16 to a transmitter processing circuit 17 which causes a signal representative of the ID code and the type of service required to be transmitted via the antenna 7.

The receiver stations 1, 2 and 3 are arranged in a distribution which ensures that any signal transmitted from the vehicle 5 has a high degree of probability of being received by three or more receiver stations.

Figure 3 schematically illustrates one of the receiver stations 1. It includes an internal clock 18 which is synchronised with clocks at the other receiver stations and with the base station. This synchronisation is achieved by the transmission of a clock setting signal from the base station 4 to each receiver. The receiver station receives the signal via an antenna 19 and a receive circuit 20 and the signal is transmitted along a line 21 to clock setting circuit 22. From a knowledge of the position of the receiver station relative to the base station 4 and the time represented by the signal, the clock 18 is set.

The signal transmitted from the module 6 is received via antenna 19 at receive circuit 20 and applied to a decoding circuit 23 which extracts the ID code and the code representing the type of assistance required. This information is applied to a combining circuit 24 which adds information representative of the time the signal is received by the receiver station 1. This information is then transmitted to a further combination circuit 25 which adds an identification code from store 26 which is representative of the receiver station. The combined information is transmitted at 27 to the base station 4.

The base receives information regarding the time the signal from the vehicle 5 is received at each receiver station 1, 2 and 3. As the positions of the receiver stations 1, 2 and 3 are fixed and known, and the time of reception of the signals is known, the vehicle location can be determined.

The activation of the transmission module 6 causes the ID code to be transmitted a plurality of times giving better accuracy than would be the case if only one transmission were to be made. An appropriate averaging process is carried out at the base station 4. If the vehicle is moving, this also enables the direction of travel to be determined.

When the vehicle location has been calculated at the base station 4, and also the type of assistance required has been determined, the base station 4 transmits a signal to the nearest recovery patrol vehicle or other type of service required giving vehicle details obtained from knowledge of the ID code and an exact location for the vehicle. The base station 4 also includes a facility for transmitting an acknowledgment signal to the vehicle 5 which is received by the module 6 at 28 and displayed for the driver to see at 29. Although in this embodiment of the invention, the acknowledgment is sent directly from the base station 4, in other arrangements in accordance with the invention, each receiver station includes a facility for receiving an acknowledgment signal from the base station 4 and re-transmitting it to the vehicle. The acknowledgment signal is transmitted via the nearest receiver station using the receiver ID code to address the data appropriately.

Although in the arrangement shown in Figure 1, there is direct communication between each of the receiver stations 1, 2 and 3 and the base station 4, intervening relay stations may be utilised where direct signal reception between a receiver station and the base station is difficult or impossible. Also, although in the arrangement, the base station 4 is shown to be distinct from the receiver stations 1, 2 and 3, it could also be arranged to act as a receiver station itself.

In another embodiment of the invention, the signal transmitted via the module 6 when activated includes a series of timing pulses in addition to the ID code and the information regarding the type of service required. The timing pulses are transmitted first and after a set number of such pulses, for example ten, the ID code is transmitted and then the code representing the required service.

The receiver stations include additional signal processing circuitry as illustrated in Figure 4. The signal transmitted from the module 6 is received at antenna 19 and receiver circuit 20 and passed to a signal processing circuit 30. The timing signals are applied to a counter 31 which is incremented by 1 on receipt of each timing signal and after ten such signals have been received, the expected ID signal and service ID code are applied on the output of the signal processing circuit 30 to the combining circuit 24. If identification for any reason the ID code is not received after the expected time, an alert code from store 32 is accessed instead and applied to the output. This is transmitted to the base station and acts as an alert to the effect that an emergency transmission has been made but the ID code is not yet available.If information has received from sufficient other receiver stations, the timing information from that station which did not receive the ID code may still be utilised in determining the vehicle location.

In another arrangement, the signal transmitted by the module 6 includes a plurality of timing pulses, each of which contains information identifying its position in the sequence of timing pulses. Thus, when the third timing pulse is received, the count circuit 31 notes that a timing pulse has been received and also that it is the third expected one. If the next detected timing pulse is the fifth, it still enables the identification code time slot to be determined even if difficulties in reception exist.

The module 6 may be modified so as to include an alarm button so that when activated, as well as summoning assistance, the module acts a personal alarm to frighten any attacker away. This form of signal is particularly suitable for use by pedestrians for example.

Claims (7)

1. An arrangement for determining the location of an object or person comprising: a transmitter adapted to be carried by said object or person, a plurality of receiver stations for receiving signals transmitted by the said transmitter, a base station and means for determining the relative times of reception of a signal transmitted by said transmitter at the receiver stations.

2. An arrangement as claimed in claim 1 wherein each receiver station includes a clock for timing receipt of a received signal and the arrangement including means for synchronising the clocks of the receiver stations.

3. An arrangement as claimed in claim 1 or 2 wherein the signal transmitted by the transmitter includes a code identifying the object or person.

4. An arrangement as claimed in claim 1, 2 or 3 wherein the signal transmitted by the transmitter includes information representative of the type of service required by the object or person.

5. An arrangement as claimed in claim 3 or 4 and including timing signals transmitted prior to the transmission of the code and/or information.

6. An arrangement as claimed in any preceding claim and including means for transmitting information from the base station to the object or person.

7. An arrangement for determining the location of an object or person substantially as illustrated in and described with reference to Figures 1, 2 and 3 or Figure 4 of the accompanying drawings.