Abstract:
A tracking system comprises an arming unit, a motion sensor, a direction sensor, a processor, and a transceiver. The arming unit is switchable so as to place the tracking system in either an armed state or an unarmed state. The motion sensor is arranged to activate the tracking system when the system is in an armed state and motion is detected. The direction sensor and the motion sensor output signals indicative of the direction of travel and distance travelled, respectively, to the processor when the system is activated. The processor acts upon said signals so as to generate an output indicative of the distance and direction of travel. The transceiver actuable to transmit the output of the processor to a remote base station in order that the position of a tracked object can be monitored remotely.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to a tracking system and tracking method. More particularly, but not exclusively, it relates to a tracking system and method that is operable upon an unauthorised movement of an object, for example a motor vehicle. 
   2. Description of the Related Art 
   The tracking of stolen motor vehicles is well known and techniques for doing so range from the concept of an alarm sounding from which a vehicle can be audibly tracked to the use of the Global Positioning System (GPS) to track vehicles once they are known to be stolen. 
   An audible alarm is primarily a deterrent with notification of the presence of the alarm being intended to be sufficient to ward off casual or petty thieves. However, determined or professional car thieves will typically be able to disable most audible alarms either before stealing the vehicle, by use of infrared code scanners, or manually within seconds of effecting entry to the vehicle, thus giving the impression of a fake alarm or an accidental actuation of the alarm by the vehicle&#39;s owner. 
   GPS tracking systems suffer from the problem that it is necessary to have three satellites within a line of sight of the vehicle in order to be able to accurately determine the position of the vehicle. This is not always possible in the urban environment, particularly in cities, due to the surrounding buildings. This can lead to the inaccurate determination of the location of the stolen vehicle, or an imprecise location. 
   Another drawback of GPS tracking systems is that the owner must know that the vehicle has been stolen prior to the system being activated. This can give the thief a significant amount of time to get away and even cross jurisdictional boundaries. 
   WO 95/22131 discloses a tracking device in which signal strengths and identification information from cellular transmitters received at the device are retransmitted to a remote monitoring station along with information relating to the direction and distances travelled by the vehicle. A computer at the remote monitoring station determines the position of a vehicle using the information transmitted from the device. The direction and distance information is typically used when the vehicle cannot receive adequate signals from the cellular transmitters to triangulate. 
   U.S. Pat. No. 5,767,804 and U.S. Pat. No. 6,094,164 disclose a tracking system using radio direction finding and a GPS receiver. 
   WO 98/01769 discloses a tracking system using a GPS receiver and a gyroscope. 
   U.S. Pat. No. 6,327,219 discloses a system for directing a following device toward a moveable object using radio frequencies and an ultrasonic signal. 
   GB 2360588 discloses a navigation system for directing a user to a destination using GPS. 
   SUMMARY OF THE INVENTION 
   According to a first aspect of the present invention there is provided a tracking system, which is adapted to track an object independently of the processing of directionally dependent broadcast signals, comprising an arming unit, a motion detection device, a direction detection device, processing circuitry, a transmitter and an activation device; the arming unit being switchable so as to place the tracking system in either an armed state or an unarmed state, the activation device being arranged to activate the tracking system when the system is in an armed state, the direction detection device and the motion detection device being arranged to output signals indicative of the direction of travel and distance travelled, respectively, to the processing circuitry when the system is activated, the processing circuitry being arranged to act upon said signals so as to generate an output indicative of the distance and direction of travel, the transmitter being actuable to transmit the output of the processing circuitry to a remote receiving station. 
   This arrangement allows, in some embodiments, the instantaneous commencement of tracking of, for example, a motor vehicle as soon as it is used or starts to move and the tracking system is armed. As the system requires no visible or audible output it can be concealed and is therefore not easily circumvented. Also the system does not rely upon any external signal sources, such as satellites in GPS, or land based or triangulation signals. The system can therefore be operated in urban environments where multiple reflections and variations in the path between a transmitter and the system, for example the construction of a new building, can lead to inaccuracies in position determination using such methods as triangulation based upon received signal direction or signal strength measurements. Additionally, the lack of reliance upon external signal sources allows the system to be utilised in rural areas where transmitter coverage is poor or non-existent. 
   The removal of the necessity for triangulation measurements reduces the complexity of construction of the system compared to prior art systems as signal strength measurement circuitry can be omitted. Also the processing power required at the remote receiving station is reduced over prior art devices as there is no need to perform a comparison of signal strengths in order to determine the location of the system. 
   The arming unit may be a key and lock arrangement. Alternatively, the arming unit may be an infrared transmitter and receiver arrangement. The infrared transmitter may include a signal coder and the infrared receiver may include a complementarily arranged signal decoder. 
   This allows, in the case of, for example, a motor vehicle driver to arm the system upon exiting the vehicle by, for example, locking the doors by either using a key and lock arrangement or an infrared remote locking arrangement. 
   The activation device may be any one, or combination of, the following: the motion detection device, the direction detection device, an engine monitoring device (for example a rev counter), a vibration sensing device, an engine emission sensing device, a braking sensing device (for example a handbrake). 
   The motion detection device may be a distance meter, for example an odometer, or a cable attached to an odometer, an axle or a wheel, Alternatively or additionally the motion detection device may include velocimeter and/or an accelerometer. The velocimeter and/or the accelerometer may have a complementary clock coupled thereto. The motion detection device may include an inertia activated motion switch. The motion detection device may be electronic, preferably digitised. 
   In the case of an odometer the distance travelled can be directly measured, typically to an accuracy of 0.1 km, 0.05 km or better. For a velocimeter or accelerometer, the fact that motion has started is readily detected. However, a complementary clock must be coupled thereto in order to determine the distance travelled. The use of a discrete velocimeter/accelerometer arrangement such as an inertial arrangement that is not connected to a drive mechanism allows a vehicle&#39;s motion to be tracked even if it is loaded onto a truck before being moved as it is not dependent upon the vehicle being driven. 
   The arming unit may be arranged to reset a counter in the the processing circuitry that is arranged to receive the signal input to the the processing circuitry from the motion detection device upon being switched to the armed state. 
   This arrangement resets the measured distance travelled each time the system is armed so that the total distance measured from activation of the system is a true reflection of the distance travelled. 
   The direction detection device may be a compass. Alternatively or additionally the direction detection device may be a gyroscope. The direction detection device may be electronic, preferably digitised. 
   The direction detection device may be arranged to output the signal indicative of the direction of travel to the processing circuitry either periodically or upon a significant change in direction. The time between the output of the signal may be between any pair of the following: 0.1 s, 1 s, 5 s, 10 s, 30 s, 1 min, 5 min, 15 min. A significant change of direction may be a variation in heading of between any pair of the following values: 0°, 10°, 20°, 30°, 45°, 60°, 90°, 180°, 270°, 360°. 
   This arrangement allows for only the periodic transmission of information to the remote receiving station thereby reducing the data transmission across a network and thereby minimising cost. Thus the transmitter may be arranged to transmit data as any one of: a burst of a single distance/direction pair, a plurality of distance/direction pairs or a continual feed of distance/direction pairs. The upload of a history of movement of an object including the system in a burst of data allows the retracing of a vehicles movement during a period in which the transmitter may have been switched off. This is not an option when the device only transmits a continuous stream of data detailing the present location of the vehicle. This may be of significance, for example, when proving that a vehicle was used in a crime in a period when the transmitter was not active. It may be possible to request the device (wirelessly and remotely) to output a report logging its past movements/positions. 
   The transmitter may be arranged to transmit a signal to the base station that is indicative of the overall distance travelled and the net direction of travel since the activation of the tracking system. 
   The transmitter may be any one or combination: of the following: a global system for telecommunication (GSM) transceiver, a general packet radio service (GPRS) transceiver or a third generation (3G) cellular transceiver. The transmitter may be arranged to transmit any one, or combination, of the following to the remote base station: SMS text message, e-mail, voice message. The transmitter may be arranged to open a channel to the remote receiving station periodically, or it may maintain an open channel to the remote receiving station, once the system has been activated. The transmitter may be arranged to open a channel to the remote receiving station covertly whilst the tracking system is activated. 
   The use of cellular telecommunications infrastructure allows a variety of formats of data to be transmitted. In particular with GPRS and 3G where users are billed on the basis of their use of bandwidth rather than their usage time it is feasible to maintain a low data rate channel open almost permanently for minimal cost to the user. 
   The transmitter may be arranged to receive a signal from a waymarker. The waymarker&#39;s signal may contain details of its geographical location. The processing circuitry may be arranged to reset the counter therein when the transmitter receives the signal from the waymarker. The transmitter may be arranged to transmit the details of the waymarker&#39;s geographical location to the remote receiving station. 
   Waymarkers are typically short range transmitters at the side of the road, for example, at motorway junctions, that broadcast their exact location over a small area. Such a signal would not be directionally dependent but typically would broadcast locational information to devices within a short range, typically 100 m, that they were at a specific location, for example a specific freeway off-ramp. The distance measurement may then be reset and cumulative errors associated with such a measurement are avoided. Similarly, the waymarker may be arranged to broadcast very short range signal, for example of the order of 5 m, 10 m, 20 m or so, such that it encompasses only a number of lanes of traffic, for example traffic travelling in one direction. Such a signal may contain details of direction of travel, for example Westbound versus Eastbound, and the direction measurement can be reset. The retransmission of the information transmitted by the waymarker to a remote receiving station by the device allows periodic updates of the position of the vehicle without requiring computationally intensive calculations to be carried out. 
   Waymarkers can be used to reset the “distance counter” and provide new datums for calculating the distance travelled and direction of travel. This aims to obviate the inherent problems of inaccuracies in distance meters and compasses/gyroscopes which will always drift over time. 
   The processing circuitry may be a central processor unit (CPU) with associated memory. The processing circuitry may have a data file corresponding to a map stored therein. The processing circuitry may be arranged to determine the distance and direction travelled from a known location in order to ascertain co-ordinates on the map of the systems location. The processing circuitry may be arranged to pass the co-ordinates to the transmitter, which may be arranged to transmit the co-ordinates to the remote receiving station. 
   This allows, for example, a stolen vehicle to be tracked with reference to a known location on a reference map. The known location can be the last known position of the vehicle or a known waymarker. Thus, the exact location of the vehicle can be passed to the receiving station. The vehicle may always track itself. 
   The arming unit may be a keyboard. The keyboard may be arranged to enter a code to the processing circuitry. The keyboard may be arranged to enter a numerical value to the processing circuitry. The numerical value may be a value read from the motion detection device. 
   The keyboard allows arming and disarming codes to be entered into the system. Additionally if, for example, a vehicle does not have a digital distance meter, from which a reading can be automatically scanned by the the processing circuitry, the keyboard allows a distance reading to be entered into the system upon which the distance travelled once the system is activated is then based. 
   The remote receiving station may be a mobile telecommunications device such as, for example, a telephone or a personal digital assistant (PDA). Alternatively, or additionally, the remote receiving station may be a computer, for example a PC. The remote receiving station may be situated in a law enforcement agency&#39;s office, a company&#39;s office or a users home. There may be a plurality of remote receiving stations arranged to receive the transmission from the transmitter. 
   The use of a mobile device, for example a mobile, telephone, allows an owner of, for example, a vehicle being tracked to be directly notified of the vehicle&#39;s location. Alternatively, details of the vehicles journey can be downloaded to a PC, for example, to allow sales reps journey details to be checked against their claimed journeys. 
   There may be a plurality of tracking systems distributed about an object to be tracked. The plurality of tracking systems may be comprised of dissimilar components. This allows for a tracking system to be placed where it can be easily discovered thus lulling a thief whilst they are still tracked by a better concealed tracking system. 
   The system may be housed in a motor vehicle and may be arranged to track the motor vehicle when activated. 
   According to a second aspect of the present invention there is provided a method of tracking an object comprising the steps of:
         (i) activating a tracking system;   (ii) measuring the direction and distance of travel; and   (iii) transmitting the direction and distance of travel to a remote receiving station.       

   The method may include estimating the objects current location from its last known position and the aggregate direction and distance of travel. 
   The method may include activating the tracking arrangement by a signal from a motion detection device or other object use detection means. The method may include providing the motion detection device in the form of any one, or combination of the following: a velocimeter, accelerometer, a distance meter. The method may include combining the motion detection device with a clock, for example, to measure the distance of travel. The method may include measuring the direction of travel using either a compass and/or a gyroscope. The method may include measuring the direction and distance of travel using an electronic device, preferably a digital device. 
   The method may include activating the tracking arrangement by means of any one, or combination of the following: infrared transceiver arrangement, lock and key arrangement, keyboard. 
   The method may include transmitting the direction and distance of travel periodically, for example every 30 s. The method may include transmitting a burst of direction and distance information relating to the period since the last transmission. Alternatively, or additionally, the method may include transmitting the direction and distance of travel at any significant change of direction. The method may include defining a significant change of direction as being a variation between and pair of the following values: 0°, 10°, 20°, 30°, 45°, 60°, 90°, 180°, 270°, 360°. 
   The method may include transmitting the direction and distance of travel using any one, or combination of the following telecommunications standards: GSM, GPRS, 3G. The method may include transmitting the direction and distance of travel using any one, or combination, of the following: SMS text message, e-mail, voice message. The method may include opening a communication channel to the remote receiving station, from the object periodically. Alternatively the method may include maintaining a permanently open communication channel between the object and the remote receiving station once the system has been activated. 
   The method may include receiving a signal from a waymarker by the tracking system. The method may include containing within the signal details of the waymarker&#39;s geographical location. The method may include transmitting details of the waymarker&#39;s geographical location to the remote receiving station. The method may include providing a distance meter in the system and may include resetting the distance meter upon receiving a signal from a waymarker. 
   The method may include providing the processing circuitry containing a data file corresponding to a map therein and may include determining the distance and direction travelled from a known point in order to ascertain co-ordinates on the map of the objects location. The method may include transmitting the co-ordinates to the remote receiving station. 
   The method may include providing the remote receiving station in the form of a mobile telecommunications device, such as, for example, a telephone or a PDA. Alternatively, or additionally the method may include providing the remote receiving station in the form of a computer. 
   According to a third aspect of the present invention there is provided a motor vehicle including a tracking system according to the first aspect of the present invention. 
   According to a fourth aspect of the present invention there is providing a program storage device readable by a machine and encoding a program of instructions which when operated upon the machine cause the machine to act as the tracking system according to the first aspect of the present invention. 
   According to a fifth aspect of the present invention there is provided a computer readable medium having stored therein instructions for causing a system to execute the method of the second aspect of the present invention. 
   According to a sixth aspect of the present invention there is provided a tracking system for tracking an object comprising an arming unit, a motion detection device, a direction detection device, processing circuitry, a transmitter and an activation device; the arming unit being switchable so as to place the tracking system in either an armed state or an unarmed state, the activation device being arranged to activate the tracking system when the system is in an armed state, the direction detection device and the motion detection device being arranged to output signals indicative of the direction of travel and distance travelled, respectively, to the processing circuitry when the system is activated, the processing circuitry being arranged to act upon said signals so as to generate an output indicative of the distance and direction of travel, the transmitter being actuable to transmit the output of the processing circuitry to a remote receiving station, the processing circuitry not being adapted to perform either of signal strength measurements or direction of signal determinations, upon at least two signals received from each of a plurality of transmitters in order to triangulate the position of the object. 
   Thus, such a system does not rely on triangulation of broadcast signals in order to determine the location of the object. Instead of measuring signal strengths from known transmitters or determining the direction of known transmitters this system relies upon measuring the direction of travel and the distance travelled from a previously known location. 
   According to a seventh aspect of the present invention there is provided tracking system, which tracks an object independently of the processing of directionally dependent broadcast signals, comprising an arming unit, an accelerometer, a compass, processing circuitry, and a cellular transceiver; the arming unit being switchable so as to place the tracking system in either an armed state or an unarmed state, the accelerometer being arranged to activate the tracking system when the system is in an armed state, the compass and the accelerometer being arranged to output signals indicative of the direction of travel and distance travelled, respectively, to the processing circuitry when the system is activated, the processing circuitry being arranged to act upon said signals so as to generate an output indicative of the distance and direction of travel, the cellular transceiver being actuable to transmit the output of the processing circuitry to a remote receiving station. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: 
       FIG. 1  is a schematic diagram of a prior art GPS based tracking system; 
       FIG. 2  is a block diagram of the components of a tracking system according to an aspect of the present invention; 
       FIG. 3  is a schematic diagram of a first embodiment of the tracking system of  FIG. 2 ; 
       FIG. 4  is a schematic diagram of a second embodiment of the tracking system of  FIG. 2  showing a waymarker; 
       FIG. 5  is a schematic diagram of a motor vehicle including the tracking system of FIG.  2 ; 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows a prior art global positioning system (GPS) based tracking system  100 . The system  100  comprises three GPS satellite transmitters  102   a-c , a vehicle  104  having therein a GPS receiver  106  and a transceiver  108  therein and a remote receiver  110 . 
   The three GPS satellite transmitters  102   a-c  are in precise geosynchronous orbits above the earth and broadcast signals which the GPS receiver  106  can triangulate and accurately determine the position of the vehicle  104 . When the tracking system  100  is activated, typically from a remote operations centre  112  by the manual activation of a cellular telecommunications link  114  between the operations centre  112  and the transceiver  108 , the transceiver  108  transmits the location of the vehicle  104  to the operations centre  112 . 
   The arrangement has a number of disadvantages including the obscuration of the vehicle  104  from the line of sight of the satellites  102   a,c  in  FIG. 1  by the partial wavefronts  102 ′ a,c ) by buildings  16   a,b . This, along with multiple reflection of wavefronts from the buildings  112 ,  116   a,b , results in the inaccurate or imprecise determination of the vehicle&#39;s location as it prevents accurate triangulation in the urban environment. 
   Additionally, during times of military and political tensions intentional errors are introduced into the GPS system by the military in order to prevent its utilisation by an enemy. This prevents the accurate determination of the vehicle&#39;s location. The GPS system may even be made unavailable for civilian users entirely in the future. 
   Referring now to  FIG. 2 , a tracking system  200 , which does not utilise triangulation in order to determine it&#39;s location, typically for use in a motor vehicle such as a car, comprises an arming unit  202 , a motion sensor  204 , a direction sensor  206 , a processor  208  and a cellular transceiver  210 . In this embodiment the motion sensor  204  acts as an activation means such that the system  200  becomes active once the processor  208  receives a positive indication of motion from the motion sensor  204 . 
   In use, the arming unit  202  receives an input, typically from a locking device  212  used to lock or secure the vehicle against theft. The locking device  212  can be an infrared coded transmitter, a key and lock arrangement, or a keypad for an engine immobiliser. Upon the locking device  212  being activated the arming unit  202  sends a signal to the processor  208 . The processor  208  sends activation signals to the motion sensor  204 , typically a distance meter (e.g. the vehicle&#39;s odometer), velocimeter, accelerometer, or recounter, and the direction sensor  206 , typically a compass or a gyroscope in response to the signal from the arming unit  202 . 
   The motion sensor  204  and the direction sensor  206  are typically electronic, digital devices. However, should they be non-electronic devices, there will be provided suitable monitoring circuitry arranged to enable the sensors  204 ,  206  to be monitored. It is to this monitoring circuitry that the activation signal will be sent. 
   Provided that the motion sensor  204  does not detect any movement no signal is sent to the processor. However, as soon as the motion sensor  204  detects motion of the vehicle it sends a signal to the processor  208 , which then interrogates the direction sensor  206  to determine the direction of travel of the vehicle. 
   The processor  208  passes either the raw distance and directional information or further processed information that contains an evaluated position signal of the location of, for example, a vehicle containing the system  200 , to the transceiver  210  from where it is transmitted to a base station  214 . The base station  214  will typically be a mobile telecommunications device belonging to the vehicle&#39;s owner such as a mobile telephone or a PDA. Alternatively or additionally, the base station  214  may be provided at an associated receiver at a tracking station or law enforcement agency. The base station may comprise a PC. 
   The processor  208  polls the sensors  204 ,  206  periodically, typically every few seconds, or possibly at longer intervals such as every 15 seconds and takes a direction and a distance reading that it then passes to the transceiver  210  for transmission to the base station  214 . Alternatively, the sensors  204 ,  206  may be arranged to send information to the processor  208  for transmission in response to a change in either the direction of travel or after a pre-set amount of distance of travel. The size of the change in direction of travel and/or the pre-set distance of travel are usually factor set values and will typically be around 15° and 0.16 km. 
   If a GSM connection between the transceiver  210  and the base station  214  is used it is advantageous to open a fresh connection between the transceiver  210  and the base station  214  each time the transfer of data is required as charges for GSM services are based upon a connection duration. However, if a GPRS or G3 connection is used a constantly open connection between the transceiver  210  and the base station  214  is feasible as charges are made on the basis of bandwidth utilisation in both 3G and GPRS rather than connection duration. 
   The motion sensor  204  can either measure the distance directly, in the case of a distance meter, for example a mileometer, or can be an indicator of distance, for example a velocimeter and/or accelerometer arrangement. In the case of a velocimeter and/or accelerometer arrangement the distance travelled can be calculated by monitoring the amount of time spent at each velocity and/or acceleration and applying basic kinematic models. A clock for this purpose will typically be provided as a sub-routine in the processor. 
   The locking device  212  may be a keypad as described hereinbefore. Should the motion sensor  204  not be an electronic device that is directly sampled by the processor  208  an initial starting distance value can be entered to the processor  208  by the vehicle&#39;s owner as they arm the system  200 . 
   Additional distance can be incremented to this initial value by monitoring circuitry in order to give an additional overall distance count. 
   Alternatively, whether or not the motion sensor  204  is electronic and can be directly sampled by the processor  208 , there is a counter provided within a sub-routine running on the processor  208  that is reset to zero each time the arming unit  202  sends the arming signal to the processor  208 . The counter increments in line with the distance/distance indicator signals received from the motion sensor  204  by the processor  208 . Thus, the counter effectively becomes a ‘trip counter’ for the journey that is being monitored. 
   The processor  208  can also generate and store a log of the movement of the vehicle by recording the direction of travel and aggregate distance of travel to a file each time the processor  208  receives signals from the sensors  204 ,  206 . The movement log can be downloaded either to a mobile telecommunications device via the transceiver or to a PC in order to provide analysis of the vehicle&#39;s movements, for example to check if delivery drivers have deviated from their planned routes. 
   Referring now to  FIG. 3  a tracking system  300  is installed in a vehicle  302  and comprises an arming unit, a digital distance meter  304 , a digital compass  306 , a processor  308  and a GPRS transceiver  310 . 
   The arming unit  303  comprises a key  311  and lock  312  combination. As the key  311  is turned in the lock  312  to a locked configuration the arming unit  303  sends a signal to the processor  308  which in turn interrogates the distance meter  304  and the compass  308  directly. 
   The processor  308  stores the initial distance meter reading and the initial measured compass heading. If the vehicle  302  is not moved prior to the key  311  being turned in the lock  312  to an unlocked configuration no further action is taken and the tracking system  300  is disarmed upon the arming unit  303  being in the unlocked configuration. 
   However, should the vehicle  302  be moved, as sensed by either the distance meter  304 , for example registering an increase in the distances registered thereupon of a 0.16 km or more, or the compass  306 , for example registering a significant, typically more than 15°, a signal is sent by the sensor registering the change to the processor  308 . The processor  308  interrogates the distance meter  304  and the compass  306  at regular intervals thereafter, typically between every 10 to 30 seconds. The total distance travelled and the net direction of travel can be ascertained from the final readings recorded. Also the total distance and net direction of travel can be sub-divided into time slots and the direction and distance travelled in any time slot can be found. 
   Once the system  300  is armed the GPRS transceiver opens a communication channel to a mobile telephone  314  belonging to the vehicle&#39;s owner. In the case of a GPRS mobile telephone it would be usual in this case to leave the channel permanently open as the user pays for the amount of bandwidth that he/she uses not the amount of time for which the connection is open. 
   The processor  308  passes each of the distance meter and compass readings to the transmitter to be sent to the mobile telephone  314 , typically as a SMS text message. Alternatively, the processor  308  contains a file corresponding to a map  316  containing the vehicle&#39;s initial location, which can be entered manually via a keypad typically as an address or a grid reference. 
   The map  316  can be downloaded over the communication channel from the system  300  to the telephone  314  and a marker displayed upon a screen  318  of the phone in order that the vehicle&#39;s owner can track it and can if necessary call a law enforcement agency. 
   Whilst detailed hereinbefore as a mobile telephone it will be appreciated that any suitably configured electronic device containing a GPRS transceiver will suffice as a receiver for the distance meter and compass readings, for example a suitably configured PC or a PDA. 
   Referring now to  FIG. 4  a tracking system  400  is installed in a vehicle  402  and comprises an arming device  403 , an analogue velocimeter/accelerometer arrangement  404  with monitoring circuitry  405 , an analogue gyroscope  406  with sensing circuitry  407 , a processor  408  and a GPRS transceiver  410 . 
   In this embodiment the arming device  403  is an engine immobiliser  412  that is activated by entering a code at a keypad  413 . Upon activation of the immobiliser  402 , by the entry of an arming code at the keypad a signal is sent to the processor  408  that activates the tracking system  400 . 
   Once activated the monitoring circuitry  405  and the sensing circuitry  407  monitor the motion of the vehicle  402  constantly. The circuitry  405 ,  407  send signals to the processor  408  when a significant change in velocity, typically more than 2 ms- 1 , acceleration, typically more than 5 ms- 2 , or direction, typically more than 15°, is noted. The processor  408  has a clock routine running thereupon that is used by the processor to convert the velocimeter and accelerometer readings into distances using known simple kinematic equations, e.g. s=ut+½at 2 . 
   Each time the tracking system  400  is armed a counter routine within the processor  408  is reset. This counter is incremented by a distance corresponding to the distance determined from the velocimeter and accelerometer readings. 
   The GPRS transceiver  410  establishes a connection with a telecommunications device  414 , in this case a suitably configured PC resident at the vehicle owner&#39;s base. The GPRS transceiver  410  passes the distance and direction information to the PC  414 . 
   Both the velocimeter/accelerometer arrangement  404  and the gyroscope  406  are subject to inaccuracies and drift over time, as are distance meters, whether they are analogue or digital. A waymarker  416  broadcasts a signal containing information relating to its exact geographical location. The transceiver  410  receives the waymarker&#39;s signal and passes it to the processor  408 . The processor  408  then resets the counter routine which proceeds to increment from a precisely defined geographical location. A signal containing the location of the waymarker is sent to the PC  414 . 
   It will be appreciated that although shown as digital devices the distance meter and compass of  FIG. 3  may be analogue with appropriate monitoring and/or sensing circuitry and correspondingly the analogue velocimeter/accelerometer arrangement and gyroscope may be digital devices. It will further be appreciated that the distance measuring devices may be replaced with such devices as fuel tank weight monitors or engine revolution counters. Any suitable combination of distance metering arrangements and/or direction monitoring arrangements disclosed hereinbefore may be employed to realise a tracking system in accordance with the first aspect of the present invention. 
   It will further be realised that an infrared coded ‘key’ transceiver may be used to arm a tracking system in accordance with the present invention. 
   It will also be realised that any mobile telecommunications standard, for example, GSM, G3, UTMS, GPRS may be used to transmit details of the distance and direction travelled by the vehicle, in use. 
   Referring now to  FIG. 5 , this is a flowchart detailing the steps of a method tracking an object, for example a vehicle. A tracking system is activated (Step  500 ), typically by a key, or coded input as described hereinbefore. Direction and distance sensors, of the types described hereinbefore, are interrogated by the processor to ascertain if the vehicle has moved (Step  502 ), if it has not moved the system waits and interrogates the sensors after a time delay, typically 30 seconds or so. 
   If the movement of the vehicle is detected the direction and distance sensors are used to measure the direction and distance travelled by the vehicle (Step  504 ). This information is passed to a mobile telecommunications transceiver and transmitted to a remote monitoring site (Step  506 ). 
   The sensors self-monitor to see if there is a significant change in either distance or direction (Step  508 ), if there is not they continue to self-monitor. However, if a significant change is noted in either distance or velocity the sensors measure the direction and distance of travel again (Step  504 ). Alternatively, the sensors are arranged to wait a predetermined time (Step  510 ) before measuring the direction and distance of travel (Step  512 ). 
   The transceiver may detect a waymarker and receive a signal therefrom containing detailed information relating to the geographical location of the waymarker (Step  514 ). The processor resets the measure of the distance travelled (Step  516 ) and the transceiver transmits the detailed location information relating to the waymarker to the remote monitoring site (Step  518 ). The sensors start measuring the direction of travel and the distance of travel from a precisely defined datum (Step  504 ), i.e. the location of the waymarker. 
   It will be appreciated that there are known proposals, for example the disclosure of WO98/01769, where a device is adapted to triangulate signals from a plurality of emitters placed at known locations. This is different from a system which is simpler and cannot do that, but instead uses “dead reckoning” to establish the position of the vehicle. Correcting the estimated current position of a vehicle as it passes a waymarker is simple technology to compensate for drift and accumulated errors. Being able to have the device provide, upon request, a past history of where the vehicle has been since the alarm was activated is beneficial in comparison with a system which can only report upon its present position. 
   There are a number of distinctions of embodiments of the present invention over WO98/01769 for example the structure/software running on the control processor of the device is not configured to be able to triangulate the position of the device from received triangulation signals; and/or there is no structure or software configured to evaluate signal strengths of received triangulation signals. A receiving antenna of embodiments which can detect waymarker signals indicative of their position is typically not a directional antenna.