POSITION MONITORING METHOD AND APPARATUS

Abstract: A method of, and apparatus for, monitoring the positions of one or more mobile units (3) (e.g. search and rescue personnel or vehicles on land, water and/or in the air), in which the mobile units periodically and automatically transmit information regarding their current positions to a central control (4). The latest and previous positions of one or more of the mobile units are automatically displayed simultaneously on an electronic map (7) of the area in which the mobile units are located, the position data being displayed in a variety of selectable ways. Thus, regions within the area of interest which have and have not been traversed by the mobile units are visible on the display. Environmental effects that could affect the accuracy of the displayed positions can be measured and the displayed positions updated accordingly.

Description: Position Monitoring Method and Apparatus The present invention relates to a method of and apparatus for monitoring the positions of plural mobile units and in particular to such a method and apparatus for monitoring -the positions of a plurality of members of a search and rescue party. Emergency services such as the police and mountain rescue teams often have to conduct searches for missing persons. Typically the search will be carried out by a plurality of individual searchers whose movements will be coordinated centrally by a search coordinator or controller. The individual searchers and the central search coordinator will usually be in radio communication with each other. As is known in the art the central search coordinator can be kept informed of the searcher's positions by providing each searcher with a position determining device, such as a Global Positioning System (GPS) device, and arranging for each searcher to broadcast their current position, usually periodically, to the control centre using their mobile radio. The current positions of the searchers can then be displayed, e.g. on an electronic map, to assist the search coordinator to organise the search. With the above system a search coordinator at the control centre is only informed of the current positions of the searchers and thus the Applicants have recognised that the search coordinator can only be certain of those positions which the searchers are presently searching. However, the Applicants have further recognised that, particularly in difficult terrain or in poor weather conditions, it may not be possible for the searchers to be certain always of their positions. Consequently, they may be unable to follow exactly their intended search routes . This means that some areas may remain unsearched without the knowledge of the searchers . More significantly, because the search coordinator only knows the latest positions of the searchers, he is unable to verify which parts of the search area have already been searched and therefore the search coordinator also is unable clearly to identify any unsearched areas . Thus areas may remain unintentionally unsearched. This could be a significant problem, since in many cases, for example, a person missing in mountainous terrain who is suspected of being injured, it is important that the missing person is found in as short a time as possible so that medical assistance can be administered. According to a first aspect of the present invention, there is provided a method of monitoring the positions of one or more mobile units in which the mobile units periodically and automatically transmit information regarding their current positions to a central control, comprising displaying automatically on an electronic display means the latest and previous positions of one or more of the mobile units simultaneously on a map of the area in which the mobile units are located. According to a second aspect of the present invention, there is provided an apparatus for monitoring the positions of one or more mobile units, in which the mobile units automatically periodically transmit information regarding their current positions to the apparatus, comprising: means for receiving from each mobile unit radio signals comprising the position of the mobile unit; means for storing the received position data; and electronic display means for displaying simultaneously the latest and previous received positions of one or more of the mobile units on a map of the area where the mobile units are located. According to a further aspect of the present invention, there is provided a method of coordinating a search in which plural individual searchers provide periodic updates of their current positions to a search coordinator, comprising simultaneously displaying on an electronic display means the latest and previous position of the searchers on a map of the search area and automatically updating the display with the new position of a searcher as each new position update is received but while still displaying the previous positions of the searcher on the display. In the present invention, the current and historical positions of mobile units or searchers are simultaneously displayed on a map as position data is received. This means that the central controller, e.g. search coordinator, can readily determine not only where a mobile unit, e.g. searcher is, but also where they have been. Thus it can be readily ascertained whether an area has been thoroughly searched, and, more importantly, any unsearched areas can be quickly and easily identified (and searchers directed to cover them) . The mobile units could be individual people (e.g. searchers) or groups of people on foot, or they could be vehicles such as cars or trucks, boats, helicopters or aircraft or a combination thereof. The mobile units can determine their positions using any suitable position determining means, such as a GPS system. The mobile units can transmit their positions to the central control or search coordinator using any suitable means and would typically do so via mobile radio units of a mobile radio communications system. This is convenient, since in a search, each searcher or individual team of searchers or vehicle would normally carry a mobile radio for communication with the central control. Radio communication between the mobile units and the central control may be via any suitable conventional transmission technique and may, for example, employ a slotted aloha mechanism in a trunked radio system. Thus, in the present invention, a mobile unit or searcher would .typically determine their current location using the position determining means and transmit a data message comprising their current location to the central control using a mobile radio. The position updating is preferably arranged such that each mobile radio unit broadcasts its position automatically to the central control at specified intervals or events. A position update can also be provided automatically on demand, e.g. of the central control . The current location of each of the mobile units is transmitted to the central control periodically, most preferably at predetermined regular intervals. For example the current locations could be transmitted at predetermined regular time intervals. This arrangement is more wasteful of radio time but can provide a display the density of which gives an indication of the rate at which an area has been traversed. Alternatively, the current location could be transmitted each time the mobile unit has moved a predetermined distance. In a further alternative embodiment, a grid pattern which cris-crosses the area being searched is stored and the current location of the mobile unit is transmitted when it crosses one of the pre-stored grid lines. This latter arrangement provides a neater display. Thus preferably each mobile unit stores a map of the area where it is located and a grid pattern overlying the map and periodically determines its position and transmits its position to the central control whenever it crosses a line of the grid pattern. In addition to comprising the current location of the mobile unit, the transmitted data message preferably also contains the identity of the mobile unit . It may also comprise data representing the time and date at which the position was determined. Alternatively, this time may be provided by the central control (although this would be less desirable where there are likely to be long delays . involved in transmitting and/or queuing the data message) . The central control and apparatus of the present invention store the position data and any other data transmitted such as the identity of the mobile unit, and the time and date of each position measurement. In the present invention, in addition to the current positions of the mobile units being displayed, the previous positions of the units are simultaneously displayed (i.e. both the latest and historical positions are displayed together at the same time) . The display should be made in real-time, i.e. the latest positions of the mobile units are displayed contemporaneously and automatically as the position data is received together with the historical positions of the mobile units (i.e. while the historical positions are still displayed) . In this way a direct and immediate indication of the area searched and the searchers' current locations is provided. The latest and previous positions of the mobile units may be represented on the map by appropriate symbols such as, for example, small dots. The representations preferably include the identities of the units (and different units could be distinguished by different symbols) . In a particularly preferred embodiment the present invention includes the step of or means for displaying the latest positions of the mobile units in a different manner to the previous positions, so that the current positions can be quickly and easily distinguished from the previous positions. For example, the current position symbols may be different colours, different shapes or shaded differently (especially if using a monochromatic display) . Alternatively, the symbols representing the current positions may flash on and off and those representing previous positions may continuously remain on the display. In a particularly preferred embodiment, the invention includes the step of or means for displaying the previous positions of the mobile units (i.e. in a search and rescue context, the area which has been searched) as a shaded region or regions. Most preferably, at successive updated positions within the displayed area, an area of shade proportional to area visible to the mobile unit (e.g. searcher) at each position is plotted on the display. In this way a shaded region representing the area seen by each searcher can be built up. This arrangement could be adjusted, e.g. in a predetermined manner, according to the sort of search being conducted. For example, a broad-brush search could be plotted in large regions of colour and a finger-tip search could be plotted as smaller regions or dots of colour. Thus, the combination of shaded regions produced for each searcher results in a larger shaded region depicting the total area searched. Unsearched areas would be unshaded or represented differently from the searched regions. The symbols used to represent the positions of the searchers are preferably distinguished from the shaded regions so that the searchers can be more easily identified on the display. The symbols (e.g. shading) used on the display to indicate a searched area could be made to change appearance, e.g. grow paler or to change colour, as time elapses, for example, so that a recent search of an area has a stronger colour in comparison and therefore looks 'fresher'. This could be particularly applicable to helicopter searches in which the helicopter may need to repeatedly search the same area in a short space of t ime . The present invention, particularly in its preferred embodiments, enables the search coordinator to easily and accurately identify the regions within the search area which have been searched. Any unsearched areas would also be clearly visible on the display. As the search coordinator is also informed of the searchers' current locations, he can efficiently direct the searcher (s) nearest to the unsearched area(s) to search those areas, without undue disruption to the main search and without wasting valuable search time or prolonging the search unnecessarily. The number of previous positions displayed can be selected as desired, although plural previous positions would normally be displayed for each mobile unit. Thus, for example all the stored previous positions of the mobile units could be displayed, or only a selected group of the stored positions. Preferably, only positions determined, received or transmitted within a particular or predetermined time window or range, e.g. from a particular or predetermined time to the present are displayed. In this way, the search coordinator would be able to view the extent of the area searched within a specified time, e.g. from the time at which a person was first reported missing or the search was started. Also, different time ranges could be displayed in a different manner, e.g. a different colour, to distinguish them. Further variations in displaying the positions of the mobile units are envisaged. For example, while preferably the latest and past positions of all the mobile units or searchers providing position data are displayed (such that preferably positions of plural mobile units are displayed) , it would be possible to display the positions of fewer mobile units, e.g. of subsets of the mobile units providing the position data down to displaying an individual unit only. In this arrangement the current positions of all or some units, but only the historical positions of less than all of the mobile units, could be shown . Also, the appearance (e.g. size or shape) of the symbols for each unit (e.g. the symbols indicating their current positions) could be varied to indicate the speed of movement of the unit across the ground. The mobile units could, for example, determine and transmit their speeds to the central control to allow this to be done. Alternatively, the central control could estimate a mobile unit ' s speed from the rate of change of its position. The present invention preferably further includes a step of or means for modifying the displayed previous positions of the mobile units to compensate for environmental effects or conditions that could affect the accuracy of the displayed positions, such as the effects of tide, wind and/or currents. Thus the displayed positions can be made to drift with time on the display in a particular or predetermined manner to account for this. This is particularly useful for searches over water. A preferred way of estimating environmental effects on the displayed historical positions is to release one or more free or untethered markers into the search environment and observe their position changes with time. For example, free-floating marker buoys could be dropped into water to estimate the effects of tide, wind and/or currents, etc. This gives a real-time empirical estimate of the effect of wind and/or currents, etc. on the position of a free moving body in the environment of the search, i.e. of how such effects will affect the position data displayed. The observed drift in position of the markers can then be used to modify the historical position data on the display to account for these effects. The position changes could be interpolated in both space and time to do this. The change in position of each marker can be estimated by tracking the markers over time. Each marker could be equipped with a position determining means and a transmitter, and arranged to provide position updates to the central control for this purpose. Alternatively, each marker could transmit .a marker signal that can be tracked to give the relative position changes with time of the marker. In a particular preferred embodiment the invention further includes a step of or means for displaying the last known position of a missing person in addition to the current and historical positions of the searchers. Most preferably concentric rings or contour lines showing where the person could have reached after various elapsed times are also displayed. The rings need not be circles and preferably take into account variations in terrain (such that they would not normally be circular) . For example, the rings would be shown closer together on the display in a mountainous or hilly area because the missing person would not be able to traverse such terrain as quickly as a flat area. More than one missing person or party could be monitored at one time and the areas which might be covered by the different parties could be distinguished using, for example, different colours on the display. In the above described embodiment in which rings or contour lines on the electronic map indicate distances which the missing person could have traversed in certain times, the shape of the rings could also be modified over time to take into account natural effects such as the wind, tides and currents. Other features such as, for example, road blocks and surveillance cameras could also be displayed on the map, if desired. This may be desirable where, for example, the search is for an escaped prisoner. In another preferred embodiment, the invention preferably includes a step of or means for identifying a mobile unit which has stopped moving, and then automatically changing the display to indicate this fact . This may be done by determining when a mobile unit has not changed position for a predetermined period of time. Once such a situation is detected, the stationary mobile unit (e.g. searcher) is preferably automatically identified on the display using a more prominent symbol such as, for example, a flashing indicator. This would highlight the situation to the search coordinator and allow him/her to investigate the cause. For example, such a feature may highlight that the searcher was in difficulty. Similarly, the mobile radios of the mobile units could be provided with tilt switches and arranged to transmit their current position to the central control, which is then arranged to highlight the position, automatically when the tilt switch is triggered. This enables a fallen searcher to be quickly identified. Although the invention has been described above with reference to a search and rescue application, it could be used in other situations if desired. For example a similar system may also be employed by bus or freight transport companies who wish to monitor the progress of their vehicles. The vehicles would be tracked in real-time and their positions transmitted to a control centre at pre-determined intervals and displayed. A preferred embodiment of the present invention will now be described by way of example only and with reference to the accompanying Figure which illustrates a system in accordance with the present invention. Taking as an example a search and rescue operation, each mobile unit (e.g. individual searcher or vehicle) of the search party would typically be equipped with a position determining means 1, such as a GPS system, a mobile radio unit 3 of a mobile radio communications system (such as a cellular phone or mobile radio) , and a mobile computer 2, such as a conventional laptop or palmtop computer. The mobile computer 2 is linked to and controls both the position determining means 1 and the mobile radio unit 3. In the embodiment shown in the Figure, the mobile computer, the position determining means and the mobile radio unit are shown as discrete components. However, they could be combined in an integral unit or units, if desired. The search coordinator is provided with a central control system 4 comprising a control computer 6, which includes conventional data storage means, a fixed radio unit 5 which can communicate wirelessly with the mobile radio units of the searchers, and an electronic display 7. Communication between the mobile units and the central control can be accordance with any suitable, known technique such as, for example, a slotted aloha mechanism in a trunked radio system. In use, each mobile unit or searcher would determine its current position using the position determining means, and then transmit a data message comprising, inter alia , the current position of the mobile unit to the central control or search coordinator 4 via the mobile radio unit 3. The position updating is automated under the control of the mobile computer 2 such that each mobile unit transmits its current position automatically to the central control 4 at specified time intervals or events. Each mobile unit can transmit its current position at predetermined regular time intervals. Alternatively, the current location could be transmitted each time the mobile unit has moved a predetermined distance. In a further alternative embodiment, a grid pattern which cris-crosses the area being searched is stored and the current location of the mobile unit is transmitted when it crosses one of the pre-stored grid lines. The data message transmitted by the mobile unit also contains the identity of the mobile unit, and data representing the time and date at which the position was determined in addition to its current location. Alternatively, the time and date could be provided by the central control 4. The time and date of each position measurement, as well as the identity and position of the mobile unit are stored by the control computer 6 of the central control 4. At the central control 4 , the current and historical positions of the mobile units are automatically displayed simultaneously on an electronic map display 7 of the area in which the mobile units are located (i.e. both the latest and historical positions are displayed together at the same time) as the position data is received. The map can be generated and viewed on the screen of a conventional computer monitor or it could, for example, be an optically projected image generated from an electronic source. The display is made in real time. Thus, as the position data is received from the mobile units, their current positions are automatically displayed contemporaneously together with the historical positions of the mobile units. The display 7 thus provides a convenient and automatic immediate real-time and direct indication not only of the current locations of the mobile units, but also of where they have been. Thus a search coordinator can readily distinguish searched and unsearched areas, and also which searchers are most conveniently located or suitable to cover unsearched areas. He or she can then direct the searchers accordingly (e.g. via the mobile radio link) . The latest and previous positions of the mobile units are represented on the map 7 by symbols such as, for example, small dots. The representations also include the identities of the units. The latest positions of the mobile units are displayed in a different manner from the previous positions, so that the current positions can quickly and easily be identified. The display itself and the manner of displaying the information can be arranged or modified in accordance with any or all of the preferred and optional features discussed above. Preferably the various display changes and features are arranged to occur automatically and/or in a predetermined manner. The system can also be arranged to identify a mobile unit which has stopped moving, and then automatically change the display 7 to indicate this fact . This could be done by the central computer 6 determining when a mobile unit has not changed position for a predetermined period of time. Once such a situation is detected, the stationary searcher is preferably automatically identified on the display 7 using a more prominent symbol such as, for example, a flashing indicator. This would highlight the situation to the search coordinator and allow him/her to investigate the cause. For example, such a feature may highlight that the searcher was in difficulty. Similarly, the mobile radio units 3 of the mobile units could be provided with tilt switches and arranged to transmit their current position to the central control 6, which is then arranged to highlight the position on the display 7 automatically, when the tilt switch is triggered. This enables a fallen searcher to be immediately identified. In another arrangement, the mobile computers 2 of each mobile unit could also be arranged to display maps and the positions of mobile units. They could, for example, periodically receive the data necessary to do this from the central control 4.

Claims: Claims : 1. A method of monitoring the positions of one or more mobile units in which said mobile units periodically and automatically transmit information regarding their current positions to a central control, comprising displaying automatically on an electronic display means the latest and previous positions of one or more of said mobile units simultaneously on a map of the area in which said mobile units are located. 2. A method of coordinating a search in which plural individual searchers provide periodic updates of their current positions to a search coordinator, comprising simultaneously displaying on an electronic display means the latest and previous position of said searchers on a map of the search area and automatically updating the display with the new position of a searcher as each new position update is received but while still displaying the previous positions of the searcher on the display. 3. The method according to claim 1 or 2 , wherein each mobile unit or searcher transmits its current position to the central control or search coordinator automatically at predetermined regular intervals. 4. The method according to claim 3 , wherein each mobile unit or searcher transmits its current position to the central control or search coordinator whenever it crosses a line of a predetermined grid pattern overlying the map of the area . 5. The method according to any one of the preceding claims, further comprising displaying the identity of each mobile unit or searcher on the display. 6. The method according to any one of the preceding claims, further comprising displaying the latest position of each mobile unit or searcher in such a manner that it is distinguished from the displayed previous positions of the mobile unit or searcher. 7. The method according to any one of the preceding claims, further comprising displaying each displayed previous position of a mobile unit or searcher as a shaded region, the area of each shaded region being varied in accordance with the estimated area visible to the mobile unit or searcher at the respective previous position. 8. The method according to any one of the preceding claims, further comprising changing the appearance of the displayed previous positions on the display over time to indicate less recent positions. 9. The method according to any one of the preceding claims, further comprising displaying the previous positions of the mobile units or searchers from a particular time window or range only. 10. The method according to any one of the preceding claims, further comprising varying the appearance of the displayed symbol representing a mobile unit or searcher in accordance with the speed of movement of the mobile unit or searcher across the ground. 11. The method according to any one of the preceding claims, further comprising modifying the displayed previous positions of the mobile units or searchers to compensate for environmental effects or conditions that could affect the accuracy of the displayed positions. 12. The method according to claim 11, wherein the displayed previous positions of the mobile units or searchers are made to drift over time on the display in a particular manner. 13. The method according to any one of the preceding claims, further comprising displaying the last known position of a missing person on the map of the area. 14. The method according to claim 13, further comprising displaying contour lines on the map of the area indicating where the missing person could have reached after one or more elapsed times from their last known position. 15. The method according to any one of the preceding claims, further comprising identifying a mobile unit or searcher which has stopped moving for a particular period of time, and then automatically changing the display to highlight that mobile unit or searcher. 16. An apparatus for monitoring the positions of one or more mobile units, in which said mobile units automatically periodically transmit information regarding their current positions to the apparatus, comprising : means for receiving from each mobile unit radio signals comprising the position of the mobile unit; means for storing the received position data; and electronic display means for displaying simultaneously the latest and previous received positions of one or more of said mobile units on a map of the area where said mobile units are located. 17. The apparatus according to claim 16, further comprising means for displaying the identity of each mobile unit on the map on the electronic display means. 18. The apparatus according to claim 16 or 17, further comprising means for displaying the latest position of each mobile unit in such a manner that it is distinguished from the displayed previous positions of the mobile unit on the electronic display means . 19. The apparatus according to claim 16, 17 or 18 wherein said electronic display means further comprises means for displaying each displayed previous position of a mobile unit as a shaded region, and means for varying automatically the area of each shaded region in accordance with the estimated area visible to the mobile unit at the respective previous position. 20. The apparatus according to any one of claims 16 to 19, wherein said electronic display means further comprises means for changing automatically the appearance of the displayed previous positions on the display over time to indicate less recent positions. 21. The apparatus according to any one of claims 16 to 20, further comprising means for selecting from the stored received position data, data from a particular time window or range; and means for displaying on the electronic display means the selected previous positions of the mobile units only. 22. The apparatus according to any one of claims 16 to 21, further comprising means for varying automatically the appearance of the displayed symbol representing a mobile unit in accordance with the speed of movement of the mobile unit across the ground. 23. The apparatus according to any one of claims 16 to 22, wherein said electronic display means further comprises means for modifying the displayed previous positions of the mobile units to compensate for environmental effects or conditions that could effect the accuracy of the displayed positions. 24. The apparatus according to claim 23, wherein said electronic display means further comprises means for automatically making the displayed previous positions of the mobile units drift over time on the display in a particular manner. 25. The apparatus according to any one of claims 16 to 24, further comprising means for displaying the last known position of a missing person on the map of the area on said electronic display means. 26. The apparatus according to claim 25, further comprising means for displaying automatically contour lines on the map of the area on said electronic display means indicating where a missing person could have reached after one or more elapsed times from their last known position. 27. The apparatus according to any one of claims 16 to 26, further comprising means for identifying a mobile unit which has stopped moving for a particular period of time, and means for automatically changing the display of the electronic display means to highlight that mobile unit . 28. A system for monitoring the positions of one or more mobile units, comprising an apparatus according to any one of claims 16 to 27, and further comprising one or more mobile units, each mobile unit including means for automatically transmitting its current position to the apparatus at predetermined regular intervals. 29. A system according to claim 28, wherein each mobile unit comprises means for storing a map of the area and a predetermined grid pattern overlying the map, and means for transmitting automatically the current position of the mobile unit to the apparatus whenever the mobile unit crosses a line of the grid pattern.

Inventors: RAYNE MARK WENTWORTH, RAYNE, MARK, WENTWORTH
Applicants: RAYNE MARK WENTWORTH, SIMOCO INT LTD, RAYNE, MARK, WENTWORTH, SIMOCO INTERNATIONAL LIMITED
Application year: 1998
Main classification: G01S5
IPC codes: G01S5