Tracking workers or trains in a railway tunnel

Abstract

A method of tracking a location of a worker or train 230 in a railway tunnel 210 based on a plurality of beacon signals including beacon data which are broadcast from a plurality of beacons B1, B2, B3

Description

FIELD The present disclosure relates to tracking the position of workers or trains in a railway tunnel. BACKGROUND 5 From time to time workers will inspect, repair or carry out otherwork in a railway tunnel. Examples, include, railway tunnels, such as but not limited to a tunnel of an underground railway. In order to prevent accident due to collision of a vehicle, such as a train, with the workers, a team leader of the workers may make a telephone call to a traffic controller of the railway tunnel to obtain authorisation before any work is carried out and to update the traffic controller as to the location 10 of the workers. The team leader may keep track of the workers and ensure they do not enter into a wrong area of the railway tunnel or wander outside of a designated working area. BRIEF DESCRIPTION OF THE DRAWINGS Examples of the present disclosure will be explained below with reference to the accompanying drawings, in which:- 15 Fig 1 shows an example of a network of railway tunnels; Fig. 2 shows an example of a system for tracking workers or trains in a railway tunnel according to the present disclosure; Fig. 3 shows an example method of tracking workers or trains in a railway tunnel according to the present disclosure; 20 Fig. 4A shows a prior art method of triangulating a signal source from three known positions; Fig. 4B shows an example railway tunnel in which a plurality of beacons have been placed in accordance with the present disclosure; Fig. 4C shows another example railway tunnel in which a plurality of beacons have been placed in accordance with the present disclosure; 25 Fig. 5 shows an example method of determining a location of a worker or train according to the present disclosure; Fig. 6 shows another example method of determining a location of a worker or train according to the present disclosure; Fig. 7 shows an example of beacon data generated by an example beacon according to the 30 present disclosure; 25 06 25 25 06 25 Fig. 8 shows an example of beacon data generated by an example beacon according to the present disclosure; Fig. 9 shows an example of a location data packet received by a server according to the present disclosure; 5 Fig. 10 shows an example display of worker location according to the present disclosure; Fig. 11A is a schematic diagram showing an example of a worker left behind alert condition according to the present disclosure; Fig. 11B is a schematic diagram showing an example of a worker outside designated area alert condition according to the present disclosure; 10 Fig. 11C is a schematic diagram showing an example of a proximity alert condition according to the present disclosure; Fig. 12A is a diagram showing a plurality of beacons in underground railway tunnel according to an example of the present disclosure; Fig. 12B shows an example of a beacon positioned next to a chainage plate according to an 15 example of the present disclosure; Fig. 13 shows an example of a server for tracking a location of a worker or train in a railway tunnel according to the present disclosure; Fig. 14 shows an example of a non-transitory machine readable storage medium storing instructions for tracking a location of a worker or train mobile device in a railway tunnel according 20 to the present disclosure; Fig. 15 shows an example of a non-transitory machine readable storage medium storing instructions for execution by a mobile device used in a system according to an example of the present disclosure; and Fig. 16 shows an example of a worker walking between a plurality of beacons in a railway tunnel 25 according to an example of the present disclosure. SUMMARY A first aspect of the present disclosure provides a method of tracking a location of a worker or train in a railway tunnel comprising: 30 25 06 25 a) broadcasting a plurality of beacon signals from a plurality of beacons spaced along the railway tunnel, each beacon signal including beacon data; b) configuring a mobile device of the mobile device to receive beacon signals and determine received signal strengths of the beacon signals; and 5 c) determining a location of the worker or train based on the beacon data and received signal strengths of the beacon signals; wherein determining a location of the worker or train comprises determining an average received signal strength of beacon signals received by the mobile device over a period of time for at least some of said plurality of beacons and determining the 10 location of the worker or train based on a location of a beacon which has the highest average received signal strength; and wherein the average received signal strength is a weighted average which accords a greater weight to more recently received beacon signals. In the context of this disclosure, tracking a location of a “worker or train” should be interpreted in 15 an inclusive sense, as including tracking the location of at least one worker, or tracking the location of at least one train, or tracking the location of at least one worker and at least one train. By tracking the location of workers and / or trains in the railway tunnel, safety may be improved. A further aspect of the present disclosure provides a computer-readable medium comprising instructions which, when executed by a processor, cause the processor to perform the method as 20 described herein. A further aspect of the present disclosure provides a mobile device for tracking a location of a worker or a train in a railway tunnel, the mobile device comprising a processor configured to perform the method as described herein. In an example, there is provided a server for tracking the position of workers or trains in a railway 25 tunnel, the server comprising a processor and a machine readable storage medium storing instructions which are executable to: a. receive a location information packet from a mobile device in the railway tunnel, the location information packet including received signal strengths and beacon data of a plurality of beacon signals received by the mobile device; and 30 b. determine a location of the worker or train based on the received signal strengths and beacon data in the location information packet. 25 06 25 In an example, there is provided a system comprising a server according to the second aspect of the present disclosure and a plurality of beacons spaced along a railway tunnel, each beacon configured to broadcast a plurality of beacon signals including beacon data. In an example, there is provided a machine readable storage medium comprising instructions 5 which are executable by the processor of a mobile device to receive a plurality of beacon signals including beacon data specifying a location of the beacon along a railway track, determine a received signal strength of said beacons and forward information based on said beacon data and received signal strengths to a server over a mobile telecommunications network. 10 DETAILED DESCRIPTION Various examples of the disclosure are discussed below. While specific implementations are discussed, it should be understood that this is done for illustrative purposes and variations with other components and configurations may be used without departing from the scope of the disclosure as defined by appended claims. 15 The teachings of the present disclosure make it possible to track a location of a pedestrian, such as a worker, a vehicle such as a train, or other moving object in a railway tunnel. By tracking the location of a mobile device in the railway tunnel the location of a pedestrian, worker, vehicle or object associated with the mobile device may be tracked. For example, the worker or a driver of the vehicle may carry the mobile device. In other examples, the mobile device may be integrated 20 into or installed in the vehicle or an item of clothing or a tool carried by the worker. In some examples a mobile device may be attached to a protective apparatus, such as an earthing rod or flashing red light which is carried into the railway tunnel and placed near the workers for protective purposes and the location of such apparatus may be tracked. In the context of this disclosure, a mobile device is a device which is capable of connecting to a wireless telecommunications 25 network, such as but not limited to a mobile phone. Where reference below is made to determining the location of a worker, it is to be understood that the method also may be used to determine location of a train associated with a mobile device, unless the context demands otherwise. The teachings of the present disclosure find particular application to underground railway tunnels, but may also be applied to other types of railway tunnel. The teachings of the present disclosure 30 may be implemented on a single railway tunnel or in a network of railway tunnels. By tracking the location of workers and / or trains safety may be enhanced. Fig. 1 shows an example of a network of railway tunnels 10 in an underground railway system. The network includes a plurality of underground railway tunnels 11, 12, 13, 14 and a number of stations 16. There may also be passages 15 linking the railway tunnels. Trains 20 travel along the 25 06 25 railway tunnels and stop at the stations 16. Workers 30 may walk through the railway tunnels 11, 12, 13, 14 and passages 15 linking the railway tunnels. It is to be understood that Fig. 1 is just an example and other underground railway systems may have more or fewer railway tunnels and different configurations of railway tunnels. 5 Fig. 2 shows an example of a system 200 according to the present disclosure. The system includes a plurality of beacons B1, B2, B3 which are placed in the railway tunnel 210 and a remote server 220 which is external to the railway tunnel. The beacons B1, B2, B3 may be placed at predetermined known locations spaced along the railway tunnel. In some examples the railway tunnel extend between a number of stations. The beacons may be positioned inside the tunnel at 10 locations between the stations. By positioning the beacons inside the tunnel at locations between stations, this makes it possible to track the position of workers when they are inside the tunnel and walking between the stations. In some examples the beacons may be spaced at regular intervals, for instance every 100 meters, every 50 meters or another regular interval. Each beacon B1, B2, B3 is configured to wirelessly broadcast a respective beacon signal Si, S2, 15 S3. The beacon signal of each beacon includes beacon data. The beacon data may indicate a location and / or an identity of the beacon. In one example, the beacons are Bluetooth beacons such as Bluetooth Low Energy (BLE) beacons or iBeacons. In another example, the beacons may be wifi beacons using a wireless local area network (WLAN) protocol, such as the 802.11 standard protocol. The beacon signals may be broadcast periodically so that over a period of time each 20 beacon broadcasts a plurality of beacon signals. A pedestrian, such as a worker 230, may walk up and down the railway tunnel 210. The worker may carry a mobile device 240 for example in their hands or a pocket or the mobile device may be attached to or installed in an item of clothing such as a helmet, footwear or jacket or in a work tool of the worker. In one example the mobile device is a dedicated mobile device for tracking a 25 position of the worker. In another example the mobile device is a mobile phone. Where the mobile device is a mobile phone, a worker tracking application may be installed on the mobile phone to perform the functionality described below. The mobile device 240 is configured to receive at least one beacon signal from a beacon in the railway tunnel and send a location information package to a remote server based on the at least 30 one received beacon signal. The mobile device may send the location information package Mi to the remote server 220 over a mobile telecommunications network, such as a GSM, GPRS, CDMA, 3G, 4G or 5G network etc. While just one worker with an associated mobile device is shown in Fig. 2, it is appreciated that there may be many workers each with their own associated mobile device. 25 06 25 The remote server 220 is a computing device including a processor and a non-transitory machine readable storage medium for storing instructions which are executable by the processor. The remote server 220 is configured to receive a location information package from the mobile device of the worker. The remote server is further configured to determine a location of the worker based 5 on the location information package. The above described system allows the location of a worker to be tracked in the railway tunnel, even if Global Positioning Service (GPS) signals are not able to penetrate the railway tunnel. This will often be the case for long railway tunnels and underground railway tunnels. Further, the system makes it possible to determine a location of a worker without the worker or team leader 10 making a telephone call to a traffic controller. In some cases the above described system may be more reliable than a telephone call, as it does not rely on a team leader to remember to call the traffic controller and avoids human error, which may for example occur if a team leader misreads a location plate in the railway tunnel or is mistaken as the location of one of the team members. Further the system may be able to continuously track a location of each worker, rather than relying 15 on ad-hoc telephone calls. This is desireable for safety reasons, especially when the worker is in a tunnel at a location between stations. As the location information packet Mi is communicated to the server 220 by the mobile device 240 of the worker, the beacons B1, B2, B3 do not need to have a wired or wireless connection to the outside of the railway tunnel. Thus compared to using radio frequency ID (RFID) tags or 20 readers, beacons avoid expensive wiring costs. Further each beacon may operate a relatively low power as each beacon just covers a length of the railway tunnel and is not required to generate a signal powerful enough to reach outside of the railway tunnel. There are various possible methods of determining a location of the worker based on the beacon signals. For instance a location of a worker may be determined to be closest to the beacon having 25 the strongest received signal strength. In one example the location of the worker is determined based on weighted averages of received signal strengths of beacon signals received by the mobile device, as the use of weighted averages helps to overcome difficulties caused by the wireless environment of the railway tunnel. Fig. 3 shows an example method 300 of tracking the location of a worker or train in a railway 30 tunnel according to the present disclosure. The method of Fig. 3 may for instance be employed in a railway tunnel as shown in Fig. 1 or Fig. 2. At block 310 a plurality of beacon signals are broadcast from a plurality of beacons spaced along the railway tunnel. Each beacon signal includes beacon data. In one example the beacon data may include a beacon identifier and / or a beacon location. The beacon location may be expressed 35 as chainage which is a unit of distance used in railways. 25 06 25 At block 320 a mobile device (which may be associated with a worker or train) is configured to receive beacon signals and determine received signal strengths of the beacon signals. For example a mobile device dedicated to this purpose may be provided to the worker by their employer or a mobile application for tracking the location of the worker may be installed on a 5 mobile phone of the worker. The mobile device may also be configured to read beacon data contained in the beacon signals, such as a beacon ID or location. At block 330 a location of the worker or train is determined based on the beacon data and received signal strengths of the beacon signals. The method of Fig. 3 may be used to determine the location of both trains and workers in a railway 10 tunnel. The method may also be used to determine the location of other pedestrians or vehicles moving in the railway tunnel. Existing systems for determining a location of a mobile device use triangulation techniques, such as that shown in Fig. 4A. Fig. 4A shows how the position of a mobile device 400 may be determined if the following are known: a position of three points P1, P2, P3 which form a triangle 15 around the mobile device 400, the distances D1, D2, D3 between the three points and the distances R1, R2, R3 between each point and the mobile device. The distances R1, R2, R3 may for example be inferred from received signal strengths if the points P1, P2, P3 send signals to or receive signals from the mobile device. Conventional triangulation techniques require a broad two dimensional spread of points P1, P2, 20 P3 with reasonably wide angles between the lines D1, D2 and D3 and thus do not work well in railway tunnel environments where the known points lie along a relatively narrow band within the railway tunnel (thus flattening the triangle) or all lie along the same line, such as a wall of the railway tunnel. Figs. 4B and 4C show examples in which beacons are deployed along a tunnel of an underground railway. 25 Fig. 4B shows an example of an up track in a first railway tunnel 410 of an underground railway and a parallel down track in a second railway tunnel 420 for trains travelling in the opposite direction. For clarity only part of the down track 420 is shown. As can be seen the beacons BIBS in railway tunnel 410 are confined to a narrow band and as the railway tunnel is slightly curved there is no clear line of sight between some of the beacons, thus making conventional 30 triangulation difficult or ineffective. Fig 4C shows a part of a first railway tunnel 430 for an up track and a second railway tunnel 440 for a down track in an underground railway. The railway tunnels are straight and beacons B1-B7 are in line with each other, making triangulation difficult or ineffective. Furthermore underground railway tunnels are a very challenging environment for wireless signals with many reflections, which can cause unexpected fluctuations in received signal strength as illustrated in Table 1. Table 1 below shows an example of received signal strengths of beacon signals at a mobile device 5 which is moving down a tunnel. The received signal strength at the mobile device of the signal from each beacon, at intervals rounded to the nearest 5 seconds, is shown in rows 4-9 of the table. The location of each beacon is shown in the second row and expressed in chainage, which is a distance measurement used in railways. CH.05.97 indicates 5.97km, while CH.06.07 indicates 6.07km. Thus in this example the beacons are spaced 100m apart. 25 06 25 Beacon No. Beacon 1 Beacon 2 Beacon 3 Beacon Location CH.05.97 CH.06.07 CH.06.17 Time (s) Received Signal Strength Received Signal Strength Received Signal Strength 0 -94 -95 -104 5 -97 -92 -103 10 -83 -93 -98 15 -99 -84 -98 20 -89 -75 -101 25 -89 -82 -99 Table 1 Although the mobile device in Table 1 is moving in a direction from Beacon 1 to Beacon 2, it can be seen that the received signal strength does not vary in linear manner with distance moved. Thus the received signal strength from Beacon 1 at time 0 seconds of -94 is weaker than the 15 received signal strength at time 10 seconds of -83, even though the mobile device has moved further away from Beacon 1 at time 10 seconds. The strongest beacon signal at each time interval is indicated in bold and underlined. It can be seen that between 0 seconds and 15 seconds the strongest received signal strength fluctuates back and forth between Beacon 1 and Beacon 2, even though during this time the mobile device is moving away from Beacon 1 and toward Beacon 8 25 06 25 2. Accordingly if the location is determined based on the strongest received signal strength alone, then the determined location may fluctuate back and forth by as much as 100m on each reading if the beacons are spaced 100m apart. This fluctuation is due to reflections in the railway tunnel. The above issues are particularly serious for underground railways. Compared to road tunnels for cars, underground railway tunnels tend to be relatively narrow and very long, e.g. having a width of 4m-6m and a length of 400-800m. In a typical example in Hong Kong, an underground railway tunnel may have a width of 5m and a length of 700m. Thus triangulation is difficult and there are more reflections from the railway tunnel walls due to the relatively narrow width compared to road tunnels. Further, whereas a system for tracking movement of a car through a tunnel may operate on the assumption that the car only moves in one direction, this is not the case for pedestrians or workers who may walk back and forth. Thus determining a location of a pedestrian or worker in an underground railway tunnel is particularly challenging. Accordingly, an example of the present disclosure proposes a method 500 of determining the location of a worker or train according to Fig. 5 to overcome the above difficulties. In one example, this method may be employed by block 330 of the method of Fig. 3 to determine the location of the worker or train. Referring to Fig. 5, at block 510, an average received signal strength of beacon signals received by the mobile device over a period of time is determined for at least some of the plurality of beacons. At block 520, a beacon having the highest average received signal strength is determined. At block 530 the location of the worker or train is determined based on a location of the beacon having the highest received average signal strength. In this way, by averaging the received signal strength over time, fluctuation in the determined location may be reduced or avoided, while still being able to detect and track a sustained change in direction of movement. The period of time is a time window (e.g. the last 25 seconds or the last 15 seconds etc), and therefore the average may be referred to as a moving average. A time window which is too long may give an out of date location of the mobile device of a worker, which may cause safety issues in a railway tunnel, as vehicles such as underground trains can travel quickly within a few minutes between stations. However, a time window which is too short may be insufficient to compensate for random fluctuations in the received signal strengths due to reflections in the railway tunnel. In one example the time window is a time window of between 15 and 30 seconds, which has been found to balance these two considerations. In one example, the average received signal strength is a weighted average which accords a greater weight to more recently received beacon signals. The received signal strength is 9 25 06 25 exponentially higher near a beacon and reduces in amplitude quickly as a worker moves away. Therefore, using a weighted average prevents the average from being dominated by large signal strengths received several time slots ago when the worker was next to a beacon, if the worker has since moved on. 5 According to one example, the method uses the following weighted average: Pbeaconl — Wl Bbeaconl(t) + W2 Bbeaconl(t"1) + ... + Wt Bbeaconl(t"T) Equation 1 Where Pbeaconi is the weighted average received signal strength for beacon 1, Wn is a weighting factor for time n and chosen to give higher weight to more recent readings, Bbeaconi(t) is the 10 received signal strength from beacon 1 at time t and T is a defined time period over which the average is taken. The time T thus corresponds to the time window discussed above. The time t may for example be a number of seconds (e.g. a fixed period of 3-10 seconds) and in some examples the time t may correspond to the period of the beacon signals or the frequency with which mobile devices are configured to scan for beacon signals. The number of samples taken 15 for each weighted average depends on the ratio of t to T. The weighted average may be recalculated every t seconds. A similar method may be used for each of the other beacons, such as beacon 2, beacon 3 etc. The location of the worker or train may then be determined based on the beacon having the highest weighted average received signal strength. The method 500 of Fig. 5 may be very processor intensive and may take some time. If the average 20 is a weighted average, then even greater demands are placed on the processor, especially if there are a large number of mobile devices whose location is to be calculated. However, determining the location of a worker or train is a time critical task and up to date information may be important for safety. Accordingly, Fig. 6 illustrates a further method 600 for determining a location of a worker or train. 25 The method 600 of Fig. 6 may consume less processor resources and / or be carried out more quickly than the method of Fig. 5. At block 610, it is determined whether a beacon signal sent by a beacon and received by the mobile device has a received signal strength above a predetermined threshold. If so, then at block 620, the location of the worker or train is determined based on the location of 30 the beacon having the received signal strength above the predetermined threshold. For example, it may be determined that the location of the worker or train is in a section of the railway tunnel proximate that beacon. 25 06 25 If no signal is above the predetermined threshold then the method of Fig. 5 is used and the average received signal strength over a period of time is determined for a plurality of beacons. The determined location of the worker or train may be approximated to the location of a beacon having the highest received signal strength or highest average received signal strength. This may 5 indicate the location of the worker or train to within 100m if the beacons are spaced 100m apart. The methods of Fig. 5 and Fig. 6 may be used to determine the location of both trains and workers in a railway tunnel. The method may also be used to determine the location of other pedestrians or vehicles moving in the railway tunnel. The method of determining the location of a worker or train as shown in Fig. 5 or Fig. 6 may be 10 refined by determining a beacon having a second highest average received signal strength and determining a location of the worker based on the location of the beacon having the highest average received signal strength and the location of the beacon having the second highest average received signal strength. In this way the worker or train may be determined as being between said two beacons. 15 Further accuracy may be achieved by taking into account the difference in average received signal strength between these two beacons. The accuracy may be further refined by taking into account a difference between the highest average received signal strength and the second highest average received signal strength. For example the determined location may be based on the location of the beacon having the highest average received signal strength, the location of the 20 beacon having the second highest average received signal strength and a difference between the highest average received signal strength and the second highest average received signal strength. The method may use a predetermined relationship between the difference between the highest average received signal strength and the second highest average received signal strength and a distance of the mobile device from the beacon having the highest average received signal 25 strength. In some examples, the method may refer to a look up table to determine a distance of the mobile device from the beacon having the highest average received signal strength, based on the difference between the highest average received signal strength and the second highest average received signal strength. For example, Fig. 16 shows an example in which a mobile device is carried by a worker W walking 30 in a railway tunnel 1600. The worker W is currently at a location having chainage CH.06.00 and is moving in the direction away from a first beacon B1 (at chainage CH.05.97) and towards a second beacon B2 (at chainage CH.06.07), while a third beacon B3 (at chainage CH.06.17) is further away from the worker. The worker’s mobile device may receive beacon signals from each of B1, B2 and B3. A weighted average may then be calculated over a time window for the received 25 06 25 signal strengths of each of the beacon signals to find the highest and second highest received signal strengths. A difference between the highest and second highest received signal strengths may also be calculated. For example, if weighting factors of Wi=0.75, W2=0.5 and W3=0.25, are used and applied to 5 Equation 1, this gives an equation for the weighted average of the received signal strength of beacon 1 at the mobile device of: P = 0.75*B (t) + 0.5*B (t-1) + 0.25*B (t-2) beaconl beaconl beaconl beaconl Equation 2 Referring to the received beacon signals in Table 1 and applying the weighted average of 10 Equation 2, over a time window (T) of 10 seconds, with a time interval (t) of 5 seconds between samples, this gives weighted averages for the received signal strengths at the mobile device of beacon signals from beacons B1, B2 and B3 at time t=10 seconds of: P = 0.75*(-83)+0.5*(-97)+0.25*(-94) = -134.25 (Highest) B1 15 P = 0.75*(-93)+0.5*(-92)+0.25*(-95) = -139.5 (Second highest) B2 P = 0.75*(-98)+0.5*(-103)+0.25*(-104) = -151 B3 Thus the first beacon B1 and the second beacon B2 have the highest and second highest received signal strengths respectively. As B1 is at CH.05.97 and B2 is at CH.06.07 this indicates 20 that the worker is between CH.05.97 and CH.06.07. At a first level of accuracy the location of the worker may be determined to be the location of B1 which has the highest weighted average received signal strength, i.e. CH.05.97. Another approach would be determine that the work was half-way between the beacons B1 and B2, i.e. CH.06.02. 25 Another approach is to take into account the difference between the highest and second highest weighted average received signal strengths, i.e. Pbi-Pb2. In this case the difference is -134.25 --139.5 = 5.25. The operator of the railway tunnel may determine a relationship between the difference between the highest and second highest weighted average received signal strengths (referred to below as 30 the ‘deviation’) and a distance (referred to below as ‘estimated distance’) of the worker from the beacon having the highest weighted average received signal strengths. For example, this relationship may be determined based on taking many readings of mobile devices of workers at known locations in the railway tunnel at different times. The relationship may be programmed into the server or other device which is to determine the location of the worker. The relationship may be entered into a look-up table. For example as shown in Table 2. Deviation Estimated Distance 1-2 50m 2-4 40m 4-6 30m 6-8 40m Table 2 25 06 25 5 Thus in the above example, where the deviation is 5.25, the estimated distance is 30m. The highest weighted average received signal strength is from beacon B1 at CH.05.97, so the worker may be determined to be at CH.05.97 plus 30m in the direction of the beacon B2 which has the second highest weighted average received signal strength. Thus the worker may be determined to be at CH.06.00 (as 30m is 0.03 chainage units), which in this example corresponds to the 10 actual location of the worker at time 10 seconds as shown in Fig. 16. It is to be appreciated that Equation 2 and Table 2 are just examples and other weighting factors, time windows and / or time intervals may be used in the weighted average and different values may be entered into the lookup table, depending on the operational conditions in the railway tunnel, calibrations and tests carried out by the railway tunnel operator. 15 While the discussion above refers to determining the location of a single worker, it is to be understood that there may be a plurality of workers each having a respective mobile device and the respective location for each worker may be determined based on the beacon data and received signal strengths of beacon signals received by the mobile device of the worker. There may also be one or more trains whose location is tracked based on mobile devices 20 associated with the trains. Blocks 310 and 320 of Fig. 3 are performed by the mobile device. In contrast, Block 330 of Fig. 3, blocks 510-530 of Fig. 5 and blocks 610-620 of Fig. 6 are in many implementations performed by the server. This is because the server has a higher processing power and higher reliability than a mobile device, (which may for example lose power) and the location of the worker is time critical 25 safety information which should be determined quickly and reliably. However, it would be possible, 25 06 25 although slower and less reliable, for these blocks 330, 510-530 and 610-620 to be performed by the mobile device or split between the mobile device and the server. The beacons are configured to periodically broadcast a beacon signal comprising beacon data. The beacon data may include a beacon identifier and / or a beacon location. Fig. 7 shows an 5 example beacon packet 700 which includes both a beacon identifier 710 and a beacon location 720. In other examples the beacon packet may simply include a beacon identifier without beacon location and the beacon location may be determined at the server by cross referencing the beacon identifier with a table of beacon identifiers and locations. Where the beacon packet includes beacon location, this may for example be expressed as a 10 distance, or as a distance in combination with other data. In one example, the beacon location includes a railway line identifier, an up line or down line identifier and a chainage. The beacon packet may also include a header and / or a footer (not shown) including data used by the wireless protocol employed by the beacon. Fig. 8 shows another example beacon packet 800. The beacon packet includes a header 810 15 which may comprise one or more beacon protocol fields. The beacon packet further includes beacon ID 820 and beacon location data 860. The location data includes a track name 830, an indicator 840 of whether the beacon is on an up track or a down track and a chainage 850 or other indicator distance. The beacon packet may also include a footer (not shown) comprising one or more beacon protocol fields. 20 In one example the beacon is an iBeacon and the header and footer comprise iBeacon protocol fields. The beacon ID and beacon location data may be included in configurable fields of the iBeacon packet. For example, the beacon ID may be included in the UIIID field and the beacon location data encoded in the major and minor configurable fields. The mobile device may be configured to periodically generate a location information packet 25 including a worker identifier and location information based on the beacon data and received signal strengths of beacon signals received by the mobile device. The mobile device may wirelessly transmit the location information packet to the server. In one example the mobile device simply collects and forwards beacon data from the beacon signals to the server with no or minimal processing. This helps to ensure the server receives the beacon data in a timely fashion. In other 30 examples the mobile device may extract relevant beacon data, such as beacon ID or beacon location, rather than forwarding the whole beacon packet to the server. Fig. 9 shows an example of a location information packet 900 sent by a mobile device. The example location information packet 900 includes a worker identifier 910 and beacon data for a plurality of beacons B1, B2, B3. Each beacon data may include a beacon identifier and a received 25 06 25 signal strength of the beacon. The beacon data may include further data derived from the beacon packets, such as beacon location. In other examples the mobile device may carry out some processing to determine the location of the worker, such as any or all of blocks 510-530 of Fig. 5 and blocks 610-620 of Fig. 6 and provide 5 the result of these blocks in a location data packet sent to the server. However, this would put a greater load on the mobile device and may result in delays in sending the data to the server. Accordingly, in most cases it is envisaged that the server will carry out the method of Figs. 5 and Fig 6 and the location information packet forwarded by the mobile device will include raw data such as beacon received signal strength, beacon ID and / or beacon location 10 Once the location of one or more workers has been determined by the server, the determined location of the worker(s) may be displayed on a display. In addition to workers, the location of trains may be determined and displayed. In one example the location of a train may be determined by a mobile device in the same manner as for the workers. For example the driver of the train may carry a mobile device for receiving beacon signals and sending location information packet 15 to the server in the same manner as the workers. Or such a mobile device may be installed on the train. An example display 1000 is shown in Fig. 10 where 1010, 1020, 1040 and 1050 denote railway tunnels, 1030 stations, T a train and Wthe location of workers. The position of each worker may be determined at regular intervals so as track movement of the workers in the railway tunnel. The 20 mobile devices may scan for beacon signals at each regular interval and the server may receive location information and determine a location of the mobile devices at each regular interval. For example the regular interval may be every 5 to 30 seconds. Tracking at intervals greater than 30 seconds may risk not detecting a dangerous situation quickly enough, as trains may take just 2 minutes to move from station to station. Tracking at intervals smaller than 5 seconds may 25 consume significant power by the mobile devices which scan for beacon signals and may negatively affect the reliability of the mobile devices due to the mobile device running low on power and delivering poor performance or the battery of the mobile device running out of power causing the mobile device to shut down. A mobile device running out of power or performing slowly due to too frequent scanning may cause safety issues, where the mobile device is being 30 used to track a position of a worker. The server may be arranged to determine whether the determined location of a worker meets an alert condition and to generate an alert in response to the alert condition being met. Figs. 11A-11C give examples of alert conditions. In these diagrams the reference numeral 1100 indicates a railway tunnel, the reference numbers Wn indicate a worker and the reference numeral T1 35 indicates a vehicle such as a train. 25 06 25 Fig. 11A shows a proximity alert condition. A proximity alert condition occurs when a worker Wi is within a predetermined distance of a vehicle Ti. Fig. 11B shows an outside of designated area alert condition. This alert condition occurs when the worker Wi is outside of a designated area 1150 for said worker. For example a designated 5 work area may be assigned to each worker or group of workers and stored in the server or a storage accessible by the server. The server may then determine whether a worker is outside of their designated area. Fig. 11C shows a worker behind alert condition which occurs when a worker Wi is more than a predetermined distance away from other workers W2-W5 in a work group to which the worker 10 belongs. In response to an alert condition being met, the server may generate an alert. The alert may for instance be displayed as a message or other indicator on the display. In some examples the alert may include a sound based alert as well. The alert may indicate the type of alert (e.g. proximity, worker outside designated area or worker left behind). 15 In one example each worker registers with the system using their mobile device before starting work, e.g. before entering the railway tunnel. For example, the worker may use an app on their mobile device and use the app to register into the system for a work assignment. In one example the worker may be presented with a QR code, e.g. on a display terminal or computer screen, when receiving the work assignment and may scan the QR code to register with the system. In 20 this way the worker may be assigned a unique worker ID by the system based on an identifier of their mobile device or based on information included in the QR code. Fig. 12A shows an example of a plurality of beacons installed in an underground railway tunnel. In this example, a first beacon 1210 is installed 100m away from a second beacon 1220. However, in other examples the beacons could be installed a different distance apart. For instance, the 25 beacons may be installed at fixed intervals of 10m to 100m depending on the budget and the resolution of location tracking required. The beacons may be placed at fixed intervals in the railway tunnel, for example every 10-100m. It can be seen that the railway tunnel is a relatively narrow and confined area which may generate many reflections of the wireless beacon signals. The location of each beacon may be determined during setup and stored in the beacon firmware, 30 the server and / or other parts of the tracking system. The beacons may conveniently be installed next to chainage plates 1230, for instance as shown in Fig. 12B. A chainage plate is a sign installed in a railway tunnel which indicates a location of the sign. Such signs are installed in many underground railway tunnels as a visual method of indicating location which a nearby worker can read. Therefore by placing a beacon next to an 25 06 25 existing chainage plate, the location of the beacon may be easily and quickly ascertained when the system is set up. Fig. 13 shows is a schematic diagram of a server 1300 for tracking the position of workers and / or trains in a railway tunnel according to the present disclosure. The server may be a single server, 5 a cluster of servers, a server service provided by a public or private cloud etc. The server may comprise a communication interface 1310, a processor 1320 and a non-transitory machine readable storage medium 1330. The communication interface 1310 facilitates communication with other devices. For example a location information packet sent by a mobile device of a worker may be received at the 10 communication interface 1310 of the server. The processor 1320 may be a microprocessor, central processing unit or other processing device and is configured to execute machine readable instructions stored on the machine readable storage medium. The machine readable storage medium 1330 stores instructions 1340 which are executable by 15 the processor. For example the storage medium may be hard disk, a memory, flash drive or other storage system which is readable by a computer. The instructions 1340 may include: a. instructions 1350 to receive a location information packet from a mobile device of a worker or train in the railway tunnel, the location information packet including received signal strengths and beacon data of a plurality of beacon signals received by the mobile 20 device; and b. instructions 1360 to determine a location of the worker or train based on the received signal strengths and beacon data in the location information packet. The instructions 1340 may include instructions to carry out any of the methods described above with reference to Figs. 1 to 12. For example, the instructions 1340 may further include instructions 25 to determine an average received signal strength as perceived by the mobile device for each of a plurality of beacons over a period of time as described in Fig. 4. The location information packet received by the server may include beacon data and received signal strengths of beacon signals received by the mobile device from a plurality of different beacons in a current time slot, e.g. as shown in Fig. 9. The instructions 1340 may include instructions to determine an average signal 30 strength over a period of time which includes a number of previous time slots. The storage medium may store other data such as a map of the railway tunnel or railway tunnel network, location of beacons in the railway tunnels, designated areas for the workers, rules defining alert conditions etc. 25 06 25 Fig. 14 shows an example of a non-transitory machine readable storage medium 1400 storing instructions 1410 for tracking a worker and / or train in a railway tunnel according to the present disclosure. For example the storage medium may be hard disk, a memory, flash drive or other storage system which is readable by a computer. The instructions are executable by a processor 5 to determine a location of a worker. The instructions may include instructions 1440 to determine an average received signal strength indicator (RSSI) over a period of time for a plurality of beacons, instructions 1450 to select a beacon having the highest average RSSI and instructions 1460 to determine a location of a worker or train based on the location of the beacon selected by the instructions 1450. As implementing this method is processor intensive, in some examples 10 (indicated in dotted lines), the instructions may further include instructions 1420 to determine if a mobile device has received a beacon signal having a RSSI over a predetermined threshold and if so to execute instructions 1430 to determine a location of a worker or train based on the location of the beacon having the RSSI over the predetermined threshold and otherwise to execute the instructions 1440 to 1460. The storage medium 1400 may further include instructions which are 15 executable by a processor for performing any of the methods described above in relation to Figs 1 to 12. Fig. 15 shows an example of a non-transitory machine readable storage medium 1500 storing instructions 1510 which are executable by the processor of a mobile device according to the present disclosure. For example the storage medium may be a read only memory (ROM), random 20 access memory (RAM), flash drive, hard drive or other storage system which is accessible by a processor of the mobile device. The instructions may include instructions 1520 to receive a plurality of beacon signals including beacon data specifying a location of a beacon along a railway track, instructions 1530 to determine a received signal strength (e.g. RSSI) of said beacon signals and instructions 1540 to forward information based on said beacon data and received signal 25 strengths to a server over a mobile telecommunications network. For example the information may correspond to a location information package as discussed in the examples above. The instructions 1510 may further include instructions to scan a bar code, to determine a worker identifier and send the unique identifier to the server so as to register the mobile device as belonging to the worker. 30 It is to be understood that any feature described in relation to any one example may be used alone, or in combination with other features described, and may also be used in combination with any features of any other of the examples, or any combination of any other of the examples.

Claims

CLAIMS 1. A method of tracking a location of a worker or a train in a railway tunnel comprising: a) broadcasting a plurality of beacon signals from a plurality of beacons spaced along the railway tunnel, each beacon signal including beacon data; b) configuring a mobile device associated with the worker or train to receive beacon signals and determine received signal strengths of the beacon signals; and Cy determining a location of the worker or train based on the beacon data and received signal strengths of the beacon signals.

2. The method of claim 1 wherein the plurality of beacons are positioned at locations in the railway tunnel between stations.

3. The method of claim 1 or 2 wherein the determined position of the mobile device is considered to be a location of the worker or train associated with the mobile device.

4. The method of claim 1 or 2 wherein determining a location of the worker or train comprises, in response to a beacon signal sent by a beacon and received by the mobile device having a received signal strength above a predetermined threshold, determining the location of the worker or train based on a location of said beacon. S. The method of claim 1 or 2 wherein determining a location of the worker or train comprises determining an average received signal strength of beacon signals received by the mobile device over a period of time for at least some of said plurality of beacons and determining the location of the worker or train based on a location of a beacon which has the highest average received signal strength.

6. The method of claim 1 or 2 comprising determining the location of the worker or train according to claim 4 if a beacon signal received by the mobile device in a current period having a received signal strength above the predetermined threshold and otherwise determining the location of the worker or train according to claim 5.

7. The method of claim 5 or 6 wherein the average received signal strength is a weighted average which accords a greater weight to more recently received beacon signals.

8. The method of any one of claims 5-7 wherein the weighted average received signal strength for each beacon is calculated according to the equation: Pbeacon = W1*Bbeacon(t) + W2*Bpeacon(t-1) + ... + Wr*Bpeacon(t-T) where Preacon is the weighted average received signal strength for beacon, W, is a weighting factor, Bhreacon(t) is the received signal strength of the signal from the beacon at the mobile device at time t, and T is a defined time period over which the weighted average is taken.

9. ‘The method of any one of claims 5-8 comprising determining a beacon having a second highest average received signal strength and determining a location of the worker or train based on the location of the beacon having the highest average received signal strength and the location of the beacon having the second highest average received signal strength.

10. The method of claim 9 wherein the location of the worker or train is determined based on the location of the beacon having the highest average received signal strength and the location of the beacon having the second highest average received signal strength and a difference between the highest average received signal strength and the second highest average received signal strength.

11. The method of any of the above claims wherein the mobile device sends the beacon data and received signal strengths to a server and the server determines the location of the worker or train based on the beacon data and received signal strengths.

12. The method of any of the above claims comprising configuring the mobile device to periodically generate a location information packet including a worker identifier and location information based on the beacon data and received signal strengths of beacon signals received by the mobile device and to wirelessly transmit the location information packet to the server.

13. ‘The method of any one of the above claims wherein the beacon data includes a beacon identifier and a beacon location.

14. The method of claim 13 wherein the beacon location includes a railway line identifier, an up line or down line identifier and a chainage.

15. ‘The method of any one of the above claims further comprising displaying the determined location of the worker or train on a display.

16. The method of any one of the above claims further comprising determining whether the determined location of the worker meets an alert condition and generating an alert in response to the alert condition being met.

17. The method of claim 16 wherein the alert condition comprises the worker being within a predetermined distance of a vehicle.

18. The method of claim 16 wherein the alert condition comprises the worker being outside of a designated area for said worker.

19. The method of claim 16 wherein the alert condition comprises the worker being more than a predetermined distance away from other workers in a work group to which the worker belongs.

20. The method of any of the above claims wherein there are a plurality of workers each having a respective mobile device and the method comprises determining a respective location for each worker based on the beacon data and received signal strengths of beacon signals received by the mobile device of the worker.

21. The method of any one of the above claims wherein the beacons are positioned at regular intervals along the length of a railway track.

22. The method of claim 21 wherein each beacon is positioned by a chainage plate of the railway.

23. The method of any one of the above claims wherein the position of the worker or train is calculated every X seconds, where X is a number between 5 and 30.

24. The method of any one of the above claims wherein the beacons are Bluetooth beacons.

25. A server for tracking the position of workers or trains in a railway tunnel, the server comprising a processor and a machine readable storage medium storing instructions which are executable to: a. receive a location information packet from a mobile device associated with a worker or train in the railway tunnel, the location information packet including received signal strengths and beacon data of a plurality of beacon signals received by the mobile device; b. determine a location of the worker or train based on the received signal strengths and beacon data in the location information packet.

26. The server of claim 25 wherein the plurality of beacons are positioned at locations in the railway tunnel between stations.

27. The server of claim 25 or 26 wherein the instructions include instructions to determine an average received signal strength as perceived by the mobile device for each of a plurality of beacons over a period of time.

28. The server of claim 25 or 26 wherein the location information packet includes beacon data and received signal strengths of beacon signals received by the mobile device from a plurality of different beacons in a current time slot and wherein the instructions include instructions to determine an average signal strength over a period of time which includes a number of previous time slots.

29. The server of any one of claims 25 to 27 wherein the instructions include instructions to perform the method of any of claims 3 to 10 or 15 to 20.

30. A system comprising a server according to any one of claims 25 to 29 and a plurality of beacons spaced along a railway tunnel, each beacon configured to broadcast a plurality of beacon signals including beacon data.

31. The system of claim 30 wherein the beacons are Bluetooth Low Energy Beacons.

32. A machine readable storage medium comprising instructions which are executable by the processor of a mobile device to receive a plurality of beacon signals including beacon data specifying a location of the beacon along a railway track, determine a received signal strength of said beacons and forward information based on said beacon data and received signal strengths to a server over a mobile telecommunications network.

33. The machine readable storage medium of claim 32 wherein the instructions include instructions to scan a bar code to determine a worker identifier and send the unique identifier to the server so as to register the mobile device as belonging to the worker.

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