GB2309132A

GB2309132A - Object location system

Info

Publication number: GB2309132A
Application number: GB9600537A
Authority: GB
Inventors: Hugh Malcolm Ian Bell
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-01-11
Filing date: 1996-01-11
Publication date: 1997-07-16
Anticipated expiration: 2016-01-11
Also published as: GB2309132B; GB9600537D0

Abstract

An object locating apparatus for connection to an object 3 which is subsequently to be located comprises a transmitter 26 and a receiver 23. The transmitter 26 is activated in response to a signal received by the receiver and the receiver is only capable of receiving signals intermittently. The apparatus is used in an object location system which comprises a network of nodes 2 where network receivers are provided and are capable of receiving a signal emitted by the transmitter 26 when the object is sufficiently close to the respective network receiver, and means for detecting the approximate location of the object at a given time by determining which of the network receivers can detect a signal emitted by the transmitter 26 at that time, and without obtaining any directional information from the network receivers. In addition a mobile receiver is provided which, once the approximate location of the object has been found, uses direction finding equipment in order to locate the object more precisely.

Description

Object Location System This invention relates to a system for locating objects, for example stolen property, and in particular to such a system employing the use of a radio transmitter for connection to the property and a network of radio receivers.

As a result of the high crime rates in many areas of the world, there is a clear demand for systems that assist in the prevention of theft and in the recovery of stolen goods. As a result of this, various systems have been proposed which are designed to assist property owners and the police in tracking down stolen goods.

One approach is to fit a radio transmitter to the property which is set to emit a particular signal. This signal is then detected by radio receivers having direction finding capability and the location of the property is thereby determined. Once such system, disclosed in US 4596988 (Wanka), is designed for locating stolen vehicles. This uses a radio receiver and transmitter hidden in the vehicle. When the vehicle is reported stolen, a radio signal is transmitted from a central location to the receiver in the vehicle and this then causes the transmitter to emit a signal. A number of radio receivers located at different places are then used to determine the direction from which the signal is emitted and the location of the vehicle is then found by means of triangulation.

A major disadvantage of this system results from the fact that the transmitter must be of comparatively low power in order for it to be sufficiently small to be concealed from a potential thief. Consequently, there will be a very limited range within which signals from it can be detected. Since thieves could move the property a significant distance before the theft is noticed, it is clearly important that this system is operative over a large area of land. As a result, a large number of receiving stations having direction finding capability will be necessary in order to provide the desired coverage and this will result in the system being expensive to implement.

According to the present invention there is provided an object radio location system comprising a first transmitter for connection to an object which is subsequently to be located, a network of first receivers capable of receiving a signal emitted by the first transmitter when the object is sufficiently close thereto, and means for determining the approximate location of the object at a given time by determining which of the first receivers detects a signal emitted by the first transmitter at that time, and without obtaining any directional information from the individual first receivers.

Thus, by means of the present invention the requirement for a large number of receivers with direction finding capability is overcome. Whilst a network of receivers is required, generally located at fixed locations, these need only be of simple construction and need have no directional capabilities.

The receiver and any other associated apparatus at a given location forms "node". The use of such simple receivers greatly reduces the cost as compared to the prior art system and also obviates the need for complex directional antenna systems. This is possible because the inventor has realised that when a network of radio receivers is used in combination with a comparatively low power transmitter, then only a small number, eg.

just one, of the receivers will detect the signal and so the stolen property must be in the region of the or those receivers. It will be appreciated that the accuracy of the system can be increased by using a low power transmitter in combination with a large network of receivers or reduced if a higher power transmitter is used with a smaller network.

In more sophisticated versions of the invention, if a group of nodes all detect a signal then the relative locations of these nodes could be considered since it is more likely that the stolen property would be towards the centre of any such group.

It will therefore be seen that in its broadest aspect, the invention provides a practical low cost system for determining the approximate location of an object, for example a stolen vehicle or other goods. In many circumstances, this information may be sufficient to enable the object to be found. For example, in a case of a large object such as a lorry trailer moving along a highway in open countryside a series of approximate locations would be sufficient to enable it to be found because the route being taken would soon become obvious.

Although in very basic embodiments of the invention a simple display could be used to indicate which of the first radio receivers has detected a transmission from the object, it is preferred that each of the first radio receivers is connected to a central computer, for example by means of the telephone network. The central computer is then arranged to determine the approximate location of the object from the signals received from the first radio receivers. However, in other circumstances more precise information may be useful and therefore preferably the system further comprises a mobile receiver having means to determine the direction from which a signal emitted by the first transmitter is coming. Thus, once the approximate location of the object has been determined, the mobile receiver can then be taken to that approximate location and its directional apparatus used to provide a more precise result. It will be appreciated that this results in a much more efficient use of comparatively expensive and complex directional radio equipment than is known from the prior art.

The mobile apparatus is preferably carried by a vehicle such as a car or motorcycle and the vehicle may in particularly preferred embodiments carry locating apparatus such as a global positioning system (GPS) of known type. Preferably, information is exchanged between the mobile apparatus and the central computer, for example by means of the cellular telephone network.

Thus, details of a code required to activate the first transmitter could be sent to the mobile unit and data regarding the position and direction of the mobile apparatus can be sent to the central computer.

Although in the simplest possible systems according to the invention, only a radio transmitter is provided for connection to the object, this results in an inefficient use of power since the transmitter will operate even when no purpose is served by its doing so.

Thus, preferably the system further comprises a second receiver for connection to the object, the second receiver being connected to the first transmitter such that the first transmitter may be actuated in response to a signal received by the second receiver.

Thus, normally the radio transmitter will transmit only when it is decided to find the object, for example following a theft, at which time a radio signal will be transmitted. When this is received by the second receiver the first radio transmitter will then be actuated. These actuation signals may be transmitted from one central second transmitter or a number of second transmitters which are preferably associated with the first receivers. This refinement provides a significant advantage since, as already discussed, it is important to keep the size of the apparatus for connection to the object to a minimum and therefore battery capacity is limited. By means of this feature, only the receiver need be continuously actuated and this will require at least an order of magnitude less power than the transmitter. Another advantage is that it is undesirable to make transmissions from the apparatus because when the apparatus is used to protect stolen goods such transmissions could assist thieves in locating and disabling the apparatus.

In a particularly preferred embodiment, the second receiver is arranged to actuate the first receiver only when it receives a predetermined code. As well as further increasing the difficulties faced by thieves who may suspect that radio location apparatus is connected to the object, this feature also greatly reduces the risk of accidental activation of the device.

The network of first radio receivers is useful for detecting almost any number of separate objects, and clearly in a commercially viable system it will be important to be able to have a large number of objects fitted with first transmitters for use with the system.

As already discussed, it is advantageous for a code to be required to actuate the radio receiver connected to the object. Provided that a sufficiently large number of codes are available, then also provided that each first radio receiver is allocated a separate code, then the desired object can be looked for in isolation.

Since it is possible that it may be necessary to search for a number of objects simultaneously, in a particularly preferred embodiment of the invention the first transmitter transmits a code which uniquely identifies the object to which it is connected.

In order to further reduce the amount of power used by the transmitter and receiver connected to the object, the second receiver may be arranged so that it is only actuated intermittently, for example every five minutes for a few seconds. In this way, the entire device is effectively switched off and will draw no electric current except for the very small amount required to operate a timer. The second receiver can then be actuated and in turn cause the transmitter to emit a signal.

A simple way to actuate the apparatus is to transmit a signal which is longer than the interval between the times when the receiver is actuated. A further refinement, however, is for the times at which the receiver is actuated to be predetermined such that a signal need only be transmitted to the second receiver at or about these times. This arrangement avoids the need for unnecessary transmissions from the second transmitter(s). Furthermore, once the receiver has been actuated, further signals can be sent to it which can be used to vary its operation. For example, the first transmitter could be set to transmit continuously or at particular intervals and the level of power used for transmission could be adjusted.

It is believed that the intermittent activation of a receiver as discussed above in itself contains inventive subject matter, and therefore, according to another aspect of the invention there is provided an object location apparatus for connection to an object which is subsequently to be located, comprising a transmitter and a receiver, wherein the transmitter is arranged to be activated in response to a signal received by the receiver and the receiver is only capable of receiving signals at intervals in time.

As previously discussed, this significantly reduces the power requirement for the apparatus as compared to the prior art systems since only some form of timing apparatus is required to be continuously powered. As is well known from the technology used in electronic watches, such circuitry can be constructed to run for years from tiny power supplies.

As such apparatus must generally be small enough to be concealed, this aspect of the invention clearly provides a highly significant advantage over the prior art systems which require continually operating transmitters and/or receivers. The arrangement also provides greater security, since even if the presence of such a device is suspected by a potential thief, it cannot be found by the thief producing a signal which mimics the signal used to activate the device, unless he is prepared to activate it for a considerable period of time. This would, of course, delay the thief and so increase the risk of his being caught. The advantage is further enhanced if a secret code is required to cause the receiver to actuate the transmitter.

As already discussed, preferably, the receiver is set to be actuated only at predetermined times and in this way the actuation signal only need be transmitted at those times.

Preferably, the apparatus is employed in a system as previously described.

It is to be understood that, although the invention has primarily been discussed in relation to the recovery of stolen objects, the invention also has other applications, for example for locating life rafts etc.

at sea, tracking animals for experimental purposes or in providing devices to assist in the finding of lost or abducted persons.

In addition, whilst the terms transmitter and receiver have been used herein this does not mean that discrete transmitters and receivers must be employed.

Indeed, in many embodiments it may be preferable to combine these in the form of a compact transceiver.

The invention also extends to methods of locating an object and therefore, from a further aspect the invention provides a method of locating an object comprising the steps of:a) connecting a radio transmitter to the object; b) providing a network of radio receivers, each of the receivers being capable of receiving a signal emitted by the radio transmitter when the object is sufficiently close thereto; c) providing means for determining the approximate location of the object at a given time by determining which of the radio receivers detects a signal emitted by the radio transmitter at that time and without obtaining any directional information from the individual radio receivers.

Preferably the method further comprises the step of using a mobile receiver to determine the direction from which the signal from the transmitter is emitted and thereby locating the object more accurately.

From a still further aspect the invention provides a method of locating an object comprising the steps of: a) connecting a transmitter and a receiver to the object, the receiver being arranged to activate the transmitter when it receives a predetermined signal; b) transmitting a signal to the receiver, thereby activating the transmitter; wherein the receiver is only capable of receiving signals intermittently. Preferably the receiver is capable of receiving a signal at a predetermined time and the signal is transmitted thereto substantially only at that time.

Certain embodiments of the invention will now be described, by way of example only, and with reference to the accompanying drawings: Figure 1 is a schematic diagram showing the methods by which a transceiver connected to an object can be actuated; Figure 2 is a schematic diagram showing the transmission of a signal from the transceiver connected to the object to transceivers at two nodes; Figure 3 is a schematic diagram showing the routing of data from the nodes to a central computer; Figure 4 is a schematic diagram which shows the transmission of signals between the object and transceivers located at nodes; and Figure 5 is a schematic diagram illustrating the connections between a timer, transmitter section and receiver section in transceiver apparatus for concealing in an object which is to be located.

As will be seen from Figure 1, a large number of nodes 2 having transceivers are provided at various locations distributed about the area in which the object locating system is to operate. The nodes do not have to be distributed in any particular pattern, although they should be fairly evenly distributed. However, it is important that the precise location of each node is known, either by means of GAS technology or, more conventionally from map references. The object 3 which is to be protected by means of the system has a further transceiver fitted to it in a concealed location. The frequencies of all of the transceivers are chosen such that signals may be exchanged between the nodes and the object and generally the same frequency (eg in the 27MHz Citizens Band) will be used for all transmissions.

The nodes are in turn connected to a central computer by means of the arrangement shown in Figure 3.

Thus, each node 2 is connected by means of electrical cable 9 to a modem 7 and then by further cables to the public telephone system 8. At some remote location, a central computer 10 is also connected to the public telephone system by means of modem 7 and cables 9.

These interconnections are purely conventional and are not therefore described further herein.

The general principle of operation is that, in the event that it is discovered that object 3 has been stolen, the transmitter located therein must be activated to cause it to transmit. As shown in Figure 1, this can be achieved either by means of a transmission from a single source 1 (of high power) that can be received in any part of the area covered by the system, and/or signals transmitted by each of the nodes 2. The latter signals are indicated by reference numeral 5 in Figure 1. In fact, as will be discussed in more detail below, the receiver connected to the object can only be received at certain times in order to conserve battery power. However, this does not affect the general principle of operation of the system.

In order to prevent accidental actuation of the system, the transceiver connected to the object will only be actuated in response to a particular coded signal (access code), for example a number transmitted in binary form by means of pulses. If the correct access code is received, then the transceiver could, if required, emit a signal which should also contain a code in order to provide a unique identification of the object. This could be a simple re-transmission of the access code. Thus, the nodes can be used to detect signals from more than one object and distinguish between them.

As may be seen from Figure 2, the signals 6 from the object will be detected by a number of nodes 2 and these nodes will then send a signal via the telephone system to the central computer 10 as previously described. In order to reduce the amount of telephone traffic, the system is arranged such that nodes need only send data via the telephone system when they receive a signal from the object (i.e. no "negative" data is sent).

The computer then establishes the telephone number from which the signal comes (and therefore identifies the node) by means of the caller identification systems provided by modern telephone exchanges and thus there is no need for the node to transmit identifying information. As locations of each of the nodes are known by the computer it is then able to find the approximate location of the object. In addition, the computer can then, again via the telephone network, cause the nodes to transmit further signals to the transceiver connected to the object, for example to cause it to operate at particular times or with a different power. Additionally, the apparatus could be interrogated to provide details of battery condition etc.

If a large area is covered by the system, it may be impractical to search the entire area simultaneously.

In this case, the nodes may be selected by the central computer in a pattern so that the areas where the object is most likely to be (for example near the location of theft) can be searched first. Thus, all of the nodes in a given area can be sent details of the missing object(s). These details include the access code of the hidden transmitter(s) and the times at which they may be actuated. Subsequently, at the correct access times, the transceivers at these nodes will simultaneously transmit the access code(s). The remaining nodes are contacted in the same way at different times and in this way, the whole area covered by the system can be systematically searched.

As already mentioned, in order to conserve power the transceiver connected to the object is not permanently activated. As may be seen from Figure 5, the transceiver comprises a power supply 20 (eg. a battery) which supplies current permanently to a timer 21. The timer controls a switch 22 such as a small relay which controls the supply of current to the receiver section 23 and in this way the receiver section is only energised at certain predetermined times for a predetermined period of perhaps only a few seconds. If during that period a signal is received from the antenna 24 and is found by the receiver 23 to carry the correct code, then the receiver 23 activates switch 25 which in turn allows current to be supplied to the transmitter section 26. Additional and conventional switching (not shown) permits the same antenna to be used to transmit and receive. Thus, in response to the correctly timed and coded signal the apparatus will transmit a signal which may also be coded as previously described.

The final stage is to the find the exact location of the object within the approximate area previously defined. This is done by means of a mobile unit which is either already in, or is taken to the area concerned.

The unit is a motorcycle which carries a searching system comprising a transceiver having a radio-frequency direction finding facility, a portable computer, a GAS system and a cellular telephone system. The known approximate location, the object's access code, actuation time and possibly other information such as a description of the object is transmitted via the cellular telephone system to the portable computer.

This then automatically actuates the transceiver to transmit the access code at the appropriate time.

When a signal is received from the object, the direction from which that signal was sent in relation to the axis of the motorcycle is determined by the direction finding equipment and transferred to the portable computer. Simultaneously, the location and velocity of the motorcycle are also determined and also transferred to the portable computer. The computer then determines the position of the motorcycle and the direction of the object and displays these on a screen, eg in the form of a map. This enables the motorcyclist to ride towards the object. The data is continuously received and processed and so, after a period of time, the location of the object can be determined by means of triangulation using data from different locations of the motorcycle. The location of the object can then be displayed on the screen. This data can then be relayed to the central computer via the cellular telephone system.

If desired, a digital cellular telephone system can be used which will enable any information available to the portable computer or the motorcycle rider to be continuously transmitted to the central computer.

There, it can be processed and interpreted and used to give further data or instructions to the motorcycle rider. This enables far more sophisticated computer systems to be employed than can be mounted on a motorcycle. For example, video images could be transmitted back to the central computer to assist in locating and directing the motorcyclist or to be stored for use as evidence when the object (eg stolen car) is found.

Eventually, when the object is located, a transmission to the central computer giving the location of the object will enable the police to be called rapidly to precisely the correct location.

Claims

1. An object radio location apparatus for connection to an object which is subsequently to be located, comprising a transmitter and a receiver, wherein the transmitter is arranged to be activated in response to a signal received by the receiver and the receiver is only capable of receiving signals intermittently.

2. Apparatus as claimed in claim 1, wherein the receiver is arranged to be activated at predetermined times.

3. Apparatus as claimed in claim 2, wherein power is only supplied to the receiver when it is activated at the predetermined times.

4. Apparatus as claimed in claim 1, 2 or 3, wherein power is only supplied to the transmitter when it is activated by the receiver.

5. Apparatus as claimed in any preceding claim, wherein the receiver is arranged only to activate the transmitter when the signal received by the receiver comprises a predetermined code.

6. An object radio location system comprising apparatus as claimed in any preceding claim, and a network of receivers each being capable of receiving a signal emitted by the transmitter of the apparatus when the transmitter is sufficiently close thereto.

7. A system as claimed in claim 6, further comprising a network of transmitters each being capable of emitting a signal for reception by the receiver of the apparatus when the apparatus is sufficiently close thereto, to activate the first transmitter.

8. A system as claimed in claim 6 or 7, further comprising means for determining the approximate location of the object by determining which of the receivers of the network detects a signal emitted by the transmitter of the apparatus, and without obtaining any directional information from the individual receivers of the network.

9. A system as claimed in claim 6, 7 or 8, further comprising a mobile receiver, the mobile receiver being capable of detecting signals emitted by the transmitter of the apparatus and having means to determine the direction from which such a signal is emitted.

10. A system as claimed in claim 9, wherein the mobile receiver is associated with a global positioning system which is arranged to determine the location of the mobile receiver.

11. A system as claimed in any of claims 6 to 10, wherein each of the receivers of the network is linked to a central computer, the central computer being arranged to determine the approximate location of the object from at least one signal received thereby from the receivers of the network.

12. A system as claimed in any of claims 6 to 11, wherein the transmitter of the apparatus transmits a code which identifies the object.

13. A method of locating an object comprising the steps of: a) connecting a transmitter and a receiver to the object, the receiver being arranged to activate the transmitter when it receives a predetermined signal; b) transmitting a signal to the receiver, thereby activating the transmitter; wherein the receiver is only capable of receiving signals intermittently.

14. -A method as claimed in claim 13, wherein the receiver is capable of receiving a signal at a predetermined time and the signal is transmitted thereto substantially only at that time.

15. An object radio location apparatus substantially as hereinbefore described with reference to the accompanying drawings.

16. An object radio location system substantially as hereinbefore described with reference to the accompanying drawings.

17. A method of locating an object substantially as hereinbefore described with reference to the accompanying drawings.