Tunnel real-time positioning system and method based on map matching

Abstract

The invention discloses a tunnel real-time positioning system and method based on map matching. The system comprises a mobile positioning terminal, a plurality of positioning anchor nodes, a switch, an edge gateway, a positioning resolving module and a management visualization platform. The plurality of positioning anchor nodes are arranged in a tunnel and are in communication connection with the edge gateway through the switch; the mobile positioning terminal comprises a processor, and an inertial observation module, a wireless module and a battery which are connected with the processor; the edge gateway is used for observing data and forwarding the data to the positioning resolving module and the management visualization platform; the positioning resolving module comprises a positioning engine and a map fingerprint database, the positioning engine executes map matching and data fusion operation on inertia priori and wireless observation data reported by the mobile positioning terminal based on tunnel topology and wireless fingerprint statistical data in the map fingerprint database, and outputs a positioning result; and the positioning result is issued to the management visualization platform for real-time display. According to the invention, the positioning precision in the tunnel environment can be effectively improved.

Description

Technical Field

[0001] This invention relates to the field of personnel positioning and safety communication technology in underground spaces, and in particular to a real-time tunnel positioning system and method based on map matching. Background Technology

[0002] In the operation and maintenance of power cable tunnels and municipal utility tunnels, inspections, repairs and emergency response require continuous positioning and two-way communication for personnel entering the tunnels. At the same time, it is also necessary to meet the safety control requirements such as electronic fences, trajectory tracking and navigation to the nearest safety exit. Existing projects usually use wired or private network intercom, leaky cable, relay enhanced communication, video surveillance and local RFID, QR code check-in and other methods. There are also solutions based on Wi-Fi, BLE fingerprint positioning, UWB time difference of arrival ranging or inertial PDR (Pedestrian Dead Reckoning).

[0003] However, traditional solutions have significant limitations in tunnel environments: First, communication and positioning reliability are insufficient. Cellular signals are often blocked in tunnels, and the construction of leaky cables and relays is complex, with high approval and maintenance costs and susceptibility to strong electromagnetic interference. Location cannot be provided by intercom alone. Video surveillance is obstructed, resulting in blind spots and making continuous tracking difficult. RFID QR codes can only be used for point-to-point check-in rather than real-time continuous positioning. Single fingerprint positioning based on RSSI is sensitive to environmental changes, and errors drift over time. UWB and TDoA solutions require high-precision clock synchronization and dense deployment, resulting in high costs and maintenance burdens. Pure PDR is affected by cumulative drift, and errors become uncontrollable over long distances. Furthermore, it is prone to loss of lock-on in uphill, downhill, turning, and fork scenarios. At the same time, many systems lack centralized power supply or backup power, and a power outage results in a complete network interruption.

[0004] Secondly, the system lacks positioning and control capabilities deeply coupled with tunnel topology. Existing platforms mostly operate with three separate systems: communication, positioning, and video. The lack of a unified time base between anchor points, switches, and gateways makes it difficult to integrate observations. Trajectory jumps and misjudgments are prone to occur at bifurcations, parallel sections, and long straight sections. There is a lack of a unified fingerprint database modeling and periodic maintenance mechanism, which cannot support closed-loop linkage to the nearest safe exit and rendezvous point. Data security and private network isolation measures are insufficient, and UPS protection and fault self-check alarms are weak, resulting in low inspection efficiency, slow emergency response, large personnel positioning errors, and difficulty in timely visualization and control of safety risks. There is an urgent need for an integrated technical solution that can achieve stable communication, continuous high-reliability positioning, and deep integration with tunnel topology and emergency linkage. Summary of the Invention

[0005] This invention provides a real-time tunnel positioning system and method based on map matching to solve the problem of poor positioning accuracy in the application of existing positioning technologies for real-time tunnel positioning.

[0006] In the first aspect, a real-time tunnel positioning system based on map matching is provided, including: a mobile positioning terminal, several positioning anchor nodes, a switch, an edge gateway, a positioning calculation module, and a management visualization platform;

[0007] The plurality of positioning anchor nodes are used to be deployed in the tunnel and are communicatively connected to the edge gateway through the switch;

[0008] The mobile positioning terminal includes a processor and connected to it an inertial observation module, a wireless module, and a battery; the processor calculates an inertial prior based on the observation data from the inertial observation module; the wireless module is used to interact with the plurality of positioning anchor nodes to acquire wireless observation data; the battery powers the mobile positioning terminal.

[0009] The edge gateway is used to acquire the observation data of the plurality of positioning anchor nodes and mobile positioning terminals, and forward it to the positioning calculation module and the management visualization platform;

[0010] The positioning calculation module includes a positioning engine and a map fingerprint database. The map fingerprint database at least pre-stores a tunnel topology composed of nodes and edges, as well as sampled wireless fingerprint statistics.

[0011] The positioning engine, based on tunnel topology and wireless fingerprint statistics in the map fingerprint database, performs map matching and data fusion operations on the inertial prior and wireless observation data reported by the mobile positioning terminal. It limits the trajectory to movement only within the permitted tunnel topology boundaries, and allows switching tunnel channels only at topology nodes and when the turning angle falls within the turning gating angle threshold range. Switching tunnel channels is prohibited at non-topology nodes. The positioning results of the personnel are output and sent to the management visualization platform for real-time display.

[0012] Furthermore, the inertial observation module includes an accelerometer, a gyroscope, a magnetometer, and a barometer. The processor performs gait event detection and heading estimation based on the observation data from the accelerometer, gyroscope, and magnetometer to form an initial inertial prior. Then, it combines the relative altitude information observed by the barometer to correct the initial inertial prior, thus obtaining the final inertial prior.

[0013] Furthermore, the aforementioned positioning anchor nodes are arranged at intervals of 30 to 60 meters on straight sections of the tunnel and at intervals of 15 to 30 meters on curves or forks in the tunnel, with an installation height of 2.2 to 2.8 meters.

[0014] Furthermore, it also includes a clock synchronization unit, used to distribute clock messages to the switch and the edge gateway, the switch forwards the clock messages to the plurality of positioning anchor nodes, thereby achieving network-wide time base alignment, and the edge gateway timestamps the received observation data according to the unified time base and performs caching and forwarding.

[0015] Furthermore, the map fingerprint database includes a tunnel topology composed of nodes and edges, restricted areas and safety exit locations, and wireless fingerprint statistics obtained by grid sampling. Each sampling point in the wireless fingerprint statistics stores at least a list of identifiers of the positioning anchor nodes visible to that sampling point and the corresponding wireless observation data, and establishes an association relationship with the edges or nodes on the tunnel topology.

[0016] Furthermore, the mobile positioning terminal also includes a security chip connected to the processor, a display, and an SOS button; the security chip is used to encrypt the data sent by the wireless module; the display is used to show positioning results, navigation prompts, and alarm status; and the SOS button is used to trigger emergency event reporting.

[0017] Furthermore, it also includes a UPS power supply, which provides backup power to the switch and edge gateway to ensure continuous operation in the event of a power outage.

[0018] Secondly, a real-time tunnel positioning method based on map matching is provided, implemented using the aforementioned real-time tunnel positioning system based on map matching. The method includes:

[0019] S1. Deploy and build a database, obtain tunnel plane and topology information and deploy positioning anchor nodes, perform walk-through surveys in the tunnel according to the grid to collect wireless fingerprint statistics data and write them into the map fingerprint database, so that the wireless fingerprint statistics data are associated with the edges and nodes on the tunnel topology.

[0020] S2. On-the-job registration: Bind the mobile positioning terminal to the personnel's identity and complete calibration and encrypted handshake;

[0021] S3. Observation and acquisition: The mobile positioning terminal acquires the observation data from the inertial observation module to calculate the inertial prior, and periodically scans or accesses the positioning anchor node through the wireless module to obtain wireless observation data. The acquired inertial prior and wireless observation data are reported to the edge gateway and then forwarded to the positioning calculation module.

[0022] S4. Fusion positioning: The positioning engine performs map matching and data fusion operations on the inertial prior and wireless observation data reported by the mobile positioning terminal based on the tunnel topology and wireless fingerprint statistics in the map fingerprint database. The trajectory is limited to movement within the permitted tunnel topology boundary. Switching tunnel channels is only allowed at topology nodes and when the turning angle falls within the turning gating angle threshold range. Switching tunnel channels is prohibited at non-topology nodes. The positioning result of the personnel is output.

[0023] S5. Navigation guidance: The management visualization platform displays the positioning results in real time and calculates the reachable path to the nearest safe exit or designated meeting point based on the positioning results.

[0024] Furthermore, during the deployment and database construction process, walking survey sampling is carried out on straight sections of the tunnel at a grid spacing of 5 to 10 meters, and the grid spacing of the sampling is increased to 3 to 5 meters at tunnel curves and forks. The wireless fingerprint data of each sampling point is written into the map fingerprint database.

[0025] Furthermore, it also includes: alarm recording, which pushes emergency events or electronic fence boundary crossing events triggered by the SOS button of the mobile positioning terminal to the management visualization platform via the edge gateway for alarm linkage, and simultaneously stores the corresponding positioning results, event information and personnel trajectory in the map fingerprint database for post-event query.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] This invention improves the stability and continuity of communication and positioning within tunnels by integrating communication and positioning units into a modular system and fusing multi-source observations. The mobile positioning terminal incorporates an inertial observation module and works with a wireless module to form a dual-channel observation system using both IMU and wireless. The positioning engine, combined with a map fingerprint database, performs data fusion calculations for map matching. Even under conditions where cellular signals are blocked, video has blind spots, and single RSSI is prone to jitter, this invention comprehensively utilizes inertial priors and wireless observations to suppress the cumulative drift of pure PDR, achieving real-time, continuous, and highly reliable personnel positioning and two-way communication in tunnel environments where global satellite navigation systems are unavailable.

[0028] This invention achieves deep coupling with tunnel topology and integrated platform management. By adopting an electronic map and fingerprint database described in the form of nodes and edges, a unified time base, and an edge-center collaborative architecture, the fusion algorithm is subject to topological constraints and path gating within the positioning engine, reducing the probability of trajectory jumps and misjudgments at locations such as forks and long straight sections. The management visualization platform integrates positioning, navigation, alarms, and trajectory tracking into a single interface, forming a closed-loop linkage of positioning, navigation, alarms, and tracking. This is beneficial for improving inspection efficiency and emergency response speed, and enhancing the safety visualization and management capabilities of tunnel operation. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of a real-time tunnel positioning system based on map matching provided in an embodiment of the present invention;

[0031] Figure 2 This is a general layout diagram of the equipment inside the tunnel provided in an embodiment of the present invention;

[0032] Figure 3 This is a hardware block diagram of a mobile positioning terminal provided in an embodiment of the present invention;

[0033] Figure 4 This is a schematic diagram comparing the personnel positioning trajectory before and after map matching, provided in an embodiment of the present invention.

[0034] Figure 5 This is a flowchart of a real-time tunnel positioning method based on map matching provided in an embodiment of the present invention.

[0035] In the diagram: 101, Positioning Anchor Node; 102, Clock Synchronization Unit; 103, Edge Gateway; 104, Positioning Engine; 105, Map Fingerprint Database; 106, Management Visualization Platform; 107, Mobile Positioning Terminal; 108, UPS Power Supply; 120, Core Switch; 121, PoE Switch; 201, Accelerometer; 202, Gyroscope; 203, Magnetometer; 204, Barometer; 205, Wireless Module; 206, SOS Key; 207, Display; 208, Security Chip; 209, Battery; 210, Processor. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0037] In the description of this invention, the term "comprising" and its variations are open terms meaning "including but not limited to". The term "based on" means "at least partially based on". The terms "one embodiment" and "an embodiment" mean "at least one embodiment". The term "another embodiment" means "at least one other embodiment". The terms "first", "second", etc., may refer to different or the same objects. Other definitions, whether explicit or implicit, may be included below. Unless explicitly indicated by the context, the definition of a term remains consistent throughout the specification.

[0038] like Figure 1 As shown, the present invention provides a real-time tunnel positioning system based on map matching, including: a mobile positioning terminal 107, a plurality of positioning anchor nodes 101, an edge gateway 103, a positioning calculation module and a management visualization platform 106.

[0039] like Figure 3 As shown, the mobile positioning terminal 107 includes a processor 210 and connected to it an inertial observation module, a wireless module 205, and a battery 209. The inertial observation module includes an accelerometer 201, a gyroscope 202, a magnetometer 203, and a barometer 204. The processor 210 performs gait event detection and heading estimation based on the observation data from the accelerometer 201, gyroscope 202, and magnetometer 203 to form an initial inertial prior. Then, it modifies the initial inertial prior by combining the relative altitude information observed by the barometer 204 to obtain the final inertial prior. The wireless module 205 establishes a wireless link with the positioning anchor nodes to interact with the anchor nodes and acquire wireless observation data. The battery 209 powers the mobile positioning terminal 107.

[0040] In some preferred embodiments, the mobile positioning terminal 107 further includes a security chip 208, a display 207, and an SOS key 206 connected to the processor; the security chip 208 is used to store device certificates and session keys and to encrypt and decrypt air interface messages and uplink messages of the wireless module 205; the display 207 is used to display positioning results, navigation prompts, and alarm status; and the SOS key 206 is used to trigger emergency event reporting.

[0041] like Figure 2 As shown, the plurality of positioning anchor nodes 101 are deployed within the tunnel and are communicatively connected to the edge gateway 103 via a switch. Specifically, the switch includes a PoE switch and a core switch. The plurality of positioning anchor nodes 101 are connected to the PoE switch 121 via Ethernet and powered by it, and communicate with the edge gateway 103 via the core switch 120.

[0042] In some preferred embodiments, a clock synchronization unit 102 and a UPS power supply 108 are also included. The clock synchronization unit 102 is used to distribute PTP / NTP time bases to the PoE switch 121 and the edge gateway 103. The switch forwards the PTP / NTP time bases to the plurality of positioning anchor nodes, thereby achieving network-wide time base alignment. The UPS power supply 108 is used to provide backup power to the PoE switch 121, the core switch 120, and the edge gateway 103 to ensure continuous operation in the event of a power outage.

[0043] The edge gateway 103 is used to acquire the observation data of the plurality of positioning anchor nodes and mobile positioning terminal 107. The edge gateway 103 timestamps the received observation data according to a unified time base and caches it, and forwards the observation data to the positioning calculation module and management visualization platform through a private network fiber optic or industrial Ethernet link.

[0044] The positioning and calculation module includes a positioning engine 104 and a map fingerprint database 105. The map fingerprint database 105 pre-stores at least the locations of restricted areas and safety exits in the tunnel topology composed of nodes and edges, as well as the sampled wireless fingerprint statistics. Based on the tunnel topology and wireless fingerprint statistics in the map fingerprint database 105, the positioning engine 104 performs map matching and data fusion operations on the inertial prior and wireless observation data reported by the mobile positioning terminal 107. In each positioning cycle, it obtains the predicted location and trajectory points of the personnel, matches the predicted trajectory points with the tunnel topology, and when it detects that the predicted trajectory point falls outside the tunnel topology boundary or the corresponding trajectory segment crosses a restricted area, the predicted trajectory point is determined as an abnormal point deviating from the tunnel passage, and the abnormal positioning point is projected onto the tunnel based on the tunnel topology. The system obtains the corrected trajectory point on the most recent channel defined in the map fingerprint database. Simultaneously, it judges the trajectory turning angle between adjacent positioning cycles and the preset turning gating angle threshold at the topology node. The trajectory is allowed to switch from the current channel to the target channel connected to it only when it passes through the topology node and the turning angle falls within the turning gating angle threshold range. When a turning angle greater than the gating angle threshold occurs at a non-topology node position, channel switching is prohibited. This limits the personnel trajectory to continuous movement only within the allowed tunnel topology boundary. Based on the corrected trajectory, the system outputs the personnel's positioning results (including position, heading, and trajectory) and sends the positioning results to the management visualization platform 106 and the mobile positioning terminal 107. The management visualization platform 106 is used for real-time display of positioning results, navigation, and electronic fence and alarm linkage.

[0045] In practice, the aforementioned positioning anchor nodes are arranged at intervals of 30 to 60 meters on straight sections of the tunnel and at intervals of 15 to 30 meters on curves or forks in the tunnel. The installation height is 2.2 to 2.8 meters, the enclosure protection level is not lower than IP54, and the Ethernet is connected after being powered by a PoE switch 121.

[0046] Specifically, the map fingerprint database 105 includes a tunnel topology composed of nodes and edges, restricted areas and safe exit locations, and wireless fingerprint statistics obtained by grid sampling. Each sampling point in the wireless fingerprint statistics stores at least a list of identifiers of the positioning anchor nodes visible to that sampling point and the corresponding wireless observation data (mean and variance of RSSI or angle of arrival or time of arrival) and establishes an association with the edges or nodes on the tunnel topology.

[0047] The mobile positioning terminal 107 is carried or worn by personnel working inside the tunnel to obtain their current location within the tunnel. Multiple positioning anchor nodes are deployed along the tunnel route. The mobile positioning terminal 107 can receive signals from each positioning anchor node 101 to perform initial positioning estimation. In this embodiment, the mobile positioning terminal 107 communicates with the positioning anchor nodes wirelessly and obtains its initial position using ranging and positioning parameters such as received signal strength, angle of arrival, or time difference of arrival. Preferably, the positioning anchor nodes can be WiFi nodes, BLE nodes, or UWB nodes, distributed throughout the tunnel to ensure that the mobile positioning terminal 107 receives sufficient signals for positioning calculations at various locations within the tunnel.

[0048] Without map matching correction, the positioning trajectory accumulated by inertial measurement may gradually deviate from the actual tunnel passage due to sensor drift errors. Especially at points where people turn or fork in the tunnel, the trajectory of pure inertial positioning may deviate from the tunnel passage or even pass through walls. For example, Figure 4 The dashed line shows the preliminary trajectory of a person calculated based on inertial measurement and wireless signals. It can be seen that the trajectory deviates from the center of the tunnel at the tunnel bend, with parts of the trajectory crossing the tunnel walls, resulting in erroneous positioning. This trajectory deviation will lead to misjudgment of the person's actual position, making it difficult to meet the requirements for accurate positioning within the tunnel. To solve the above problems, this invention introduces tunnel map data to constrain and correct the positioning results.

[0049] The map fingerprint database 105 pre-stores map data such as tunnel topology information. This tunnel topology information accurately depicts the spatial layout of the tunnel passage, including its direction, branching structure, and boundaries such as the side walls. The map data can represent the centerline and boundary range of the tunnel passage using a two-dimensional plane coordinate system. For example, the width and length of the tunnel corridor on straight sections, the turning radius, and the location coordinates of each safety exit are all recorded on the map. During the location calculation, the data fusion processing calls upon the aforementioned tunnel topology and geometric information provided by the map fingerprint database 105 as constraints to correct the location results.

[0050] like Figure 4 As shown, after data fusion processing via map matching, the personnel's location trajectory is effectively corrected. Figure 4 The solid line in the middle shows the personnel movement trajectory calculated using the system of this invention. It can be seen that the corrected trajectory is strictly confined to the inside of the tunnel passage, closely matching the tunnel orientation, and no longer deviating from the passage or passing through walls. The data fusion processing compares the initial positioning trajectory with the tunnel topology map. When it is found that the positioning point falls outside the tunnel wall or deviates from the predetermined passage center, the positioning calculation parameters are automatically adjusted and corrected so that the output positioning result is reprojected onto the tunnel passage. Specifically, in each positioning cycle, the data fusion processing first predicts the personnel's position coordinates and heading angle at the current moment based on the position, heading state, and inertial increment of the previous moment; then, it retrieves several tunnel passage centerline segments adjacent to the predicted position from the map fingerprint database 105, calculates the lateral distance from the predicted position to each candidate passage centerline segment, and calculates the angle between the current predicted heading and the orientation of each passage, selecting the passage with the smallest lateral distance as the current candidate passage. When the minimum lateral distance exceeds a preset distance threshold or the included angle exceeds a preset angle threshold, the predicted positioning point is determined to be an anomaly deviating from the tunnel passage. For anomalies, they are projected onto the centerline of the candidate passage along its normal direction to obtain corrected position coordinates, and the corresponding heading angle is adjusted to align with the passage's orientation. Simultaneously, in particle filtering or extended Kalman filtering, the original predicted state is replaced with the corrected position and heading, updating the filter state variables and covariance to reduce uncertainty in the lateral offset direction, ensuring the trajectory remains within the legal passage during subsequent iterations. This map matching process filters out accumulated inertial navigation errors, improving positioning accuracy and reliability. Through this design, real-time, high-precision positioning of personnel within the tunnel is achieved.

[0051] The above embodiments significantly improve the stability and continuity of communication and positioning within tunnels through device integration and multi-source fusion: Under the private network architecture, the positioning anchor node is aggregated to the edge gateway via PoE switch and core switch, and the UPS power supply provides power outage protection. The mobile positioning terminal has built-in accelerometer, gyroscope, magnetometer and barometer, which, together with the wireless module, form IMU and wireless dual-channel observation. The clock synchronization unit provides a unified time base. The positioning engine combines the map fingerprint database to perform map matching data fusion calculation, overcome the problems of cellular shielding, video blind spots and single RSSI jitter, suppress the cumulative drift of pure PDR and be compatible with different standards such as Wi-Fi, BLE and UWB. The security chip 208 realizes link encryption and certificate management, and achieves real-time, continuous and highly reliable personnel positioning and communication in tunnel environments where GNSS is unavailable. This invention achieves deep coupling and platform integration with tunnel topology at the system level. It adopts node-edge electronic maps and fingerprint databases, unified time base and edge-center collaboration, so that the fusion algorithm is subject to topological constraints and path gating within the positioning engine, reducing trajectory jumps and misjudgments at forks and long straight sections. The management visualization platform centralizes positioning, electronic fences, nearest safety exit path calculation, SOS alarms and trajectory tracking into a single interface, forming a closed-loop linkage from positioning, navigation, alarms and tracking. At the same time, the grid-based database construction and periodic maintenance process reduce operation and maintenance costs, improve inspection efficiency and emergency response speed, and enhance the compliance, manageability and controllability of data security and private network isolation.

[0052] Based on the above-described map-matching-based real-time tunnel positioning system, this embodiment of the invention also provides a map-matching-based real-time tunnel positioning method, such as... Figure 5 As shown, it includes the following steps:

[0053] S1. Deploy and build the database, obtain tunnel plane and topology information and deploy positioning anchor nodes, configure PoE switch 121, core switch 120 and edge gateway 103, and at the same time, establish PTP / NTP clock by clock synchronization unit 102, and perform walk-through testing in the tunnel according to grid to collect wireless fingerprint statistics data and write them into the map fingerprint database 105.

[0054] S2. On-duty registration: bind the mobile positioning terminal 107 to the personnel identity and complete the calibration and encrypted handshake (encrypted handshake with the edge gateway).

[0055] S3. Observation Acquisition: The mobile positioning terminal 107 acquires the observation data from the inertial observation module to calculate the inertial prior, and periodically scans or accesses the positioning anchor node through the wireless module 205 to obtain wireless observation data. The acquired data (including inertial prior and wireless observation data) is reported to the edge gateway 103 and then forwarded to the positioning calculation module.

[0056] S4. Fusion positioning: The positioning engine 104 performs map matching and data fusion operations on the inertial prior and wireless observation data reported by the mobile positioning terminal 107 based on the tunnel topology and wireless fingerprint data in the map fingerprint database 105. The trajectory is limited to movement within the permitted tunnel topology boundary. Switching tunnel channels is allowed only at topology nodes and when the turning angle falls within the turning gating angle threshold range. Switching tunnel channels is prohibited at non-topology nodes. The positioning result of the personnel is output.

[0057] S5. Navigation guidance: The management visualization platform 106 displays the positioning results in real time and calculates the reachable path to the nearest safe exit or designated assembly point based on the positioning results.

[0058] S6. Alarm Tracking: Emergency events or electronic fence boundary crossing events triggered by the SOS button 206 of the mobile positioning terminal 107 are pushed to the management visualization platform 106 via the edge gateway 103 for alarm linkage. At the same time, the corresponding positioning results, event information and personnel trajectory are stored in the map fingerprint database 105 for post-event query.

[0059] During the deployment and database construction process, walking survey sampling was carried out on straight sections of the tunnel at a grid spacing of 5 to 10 meters, and the grid spacing of the sampling was increased to 3 to 5 meters at tunnel curves and forks. The sampling point was stayed for 5 to 10 seconds to collect wireless fingerprint data and write it into the map fingerprint database 105.

[0060] During the fusion positioning process, particle filtering or extended Kalman filtering is used to fuse inertial prior and wireless observation data, and map constraints are applied to limit the trajectory to move only within the tunnel topology boundary. Trajectories in non-travelable areas are rejected, and inflection points are only allowed to switch at topology nodes, with gating angle thresholds set for turning.

[0061] During navigation guidance, the shortest accessible path to the nearest safe exit or designated meeting point is calculated based on the tunnel topology using the Dijkstra algorithm, and navigation prompts are sent to the mobile positioning terminal 107 and the management visualization platform 106 in the form of on-screen arrows and voice prompts, respectively.

[0062] The location data fusion process in a tunnel environment is as follows:

[0063] Step 1: Wireless Signal Positioning. The mobile positioning terminal 107 acquires wireless signal measurements from multiple positioning anchor nodes deployed within the tunnel, forming the current wireless observation data. Wireless signal positioning can obtain the initial position estimate of the personnel using fingerprint matching or geometric ranging. One implementation is to match the current wireless observation data with the wireless fingerprint data of each sampling point pre-collected in the map fingerprint database 105, and calculate the initial position of the personnel in the tunnel coordinate system based on the coordinates of one or more sampling points with the highest similarity. Another implementation is that the wireless module 205 of the mobile positioning terminal 107 receives the wireless signals from each positioning anchor node, measures parameters such as signal strength, time difference of arrival, or angle of arrival, and, combined with the known deployment positions of the positioning anchor nodes in the tunnel, calculates the initial positioning coordinates of the mobile positioning terminal 107 relative to the reference coordinate system using a geometric ranging algorithm. For example, the distance can be estimated based on the RSSI signal strength using trilateration, and the approximate location of the person can be obtained through multi-point trilateration; alternatively, the angle of arrival (AOA) positioning algorithm can be used to obtain the azimuth angle of the person relative to the positioning anchor node, and then combined with at least two positioning anchor nodes for positioning; if the positioning anchor node has time synchronization capabilities, the time difference between the mobile positioning terminal 107 and the positioning anchor node can also be calculated using the time difference algorithm to achieve precise positioning. The output of step 1 is the estimated initial wireless position of the person in the tunnel coordinate system.

[0064] Step 2: Inertial Measurement Positioning. The accelerometer 201, gyroscope 202, and magnetometer 203 of the mobile positioning terminal 107 collect inertial observation data during the wearer's movement and obtain relative displacement and orientation changes through inertial navigation calculations. Specifically, a walking positioning algorithm can be used to estimate the increment of the person's movement relative to the previously known position based on the steps detected by the accelerometer and the orientation changes detected by the gyroscope 202. This step obtains the change in the person's position over time, providing continuous trajectory information for subsequent fusion. Since inertial positioning accumulates errors over time, relying solely on Step 2 cannot provide accurate positioning in the long term, but it has high short-term dynamic accuracy and high output frequency, which can be used to smooth the person's movement trajectory during wireless signal update intervals.

[0065] Step 3: Data Pre-fusion Processing. The initial position obtained in Step S1 and the inertial displacement increment obtained in Step S2 are received, and the two types of data are preprocessed and matched in time and space. For example, the incremental trajectory of inertial positioning is superimposed on the absolute coordinates of the previous wireless positioning to obtain the predicted position at the current moment; or, when the wireless signal positioning frequency is low, inertial sensor data is used to interpolate the results of two adjacent wireless positioning operations to generate a smoother trajectory. Step 3 provides a preliminary trajectory estimate for map matching, enabling subsequent fusion algorithms to simultaneously reference information from wireless ranging and inertial estimation. In this embodiment, the data fusion processing performs time synchronization and coordinate system transformation on data from different sources, ensuring that the wireless positioning results and inertial positioning results describe the person's position within the same reference frame.

[0066] Step 4: Map Matching and Fusion Correction. The personnel trajectory obtained in Step 3 is matched and compared with the tunnel map. The positioning results are corrected using the tunnel topology and channel boundary conditions provided by the map. Specifically, in each positioning cycle, the data fusion processing module calls the tunnel centerline and its width and orientation parameters from the map fingerprint database 105. The inertial positioning trajectory and wireless positioning results are input into the particle filter or extended Kalman filter algorithm to calculate the lateral distance from the predicted position to each candidate channel centerline and the angle between the current heading and the channel orientation. When the lateral distance and angle exceed the preset threshold, the predicted point is identified as an anomaly and projected along the normal direction onto the nearest legal channel centerline. At the same time, the heading is corrected to be consistent with the channel orientation. The corrected position and heading replace the original state and update the filter covariance, so that the trajectory of subsequent iterations is always confined to the inside of the channel. In addition, combined with the topological node information in the map, channel switching is allowed only when the trajectory passes through a node and the turning corner is within the gate control angle range. Large angle turns or cross-channel jumps at non-node locations are rejected, thus outputting a corrected trajectory consistent with the tunnel topology. Step S4 outputs the corrected current position coordinates of the personnel and the updated motion trajectory, which significantly improves the positioning accuracy and reliability.

[0067] Step 5: Output Results. The corrected positioning results are output for user and system use. The display 207 of the mobile positioning terminal 107 can highlight the personnel's location and direction of movement on a map interface, and can also indicate the location of the nearest safety exit, facilitating personnel navigation and escape; in addition, the positioning results are displayed through the management visualization platform 106. Through the above output methods, the positioning results can be applied to tunnel safety management in a timely manner.

[0068] Step 6: Positioning Loop. The above positioning process can be repeatedly executed at preset time intervals or event triggers to achieve continuous real-time positioning tracking. During continuous operation, steps 1 to 5 are repeated periodically, continuously incorporating new sensor data into the positioning calculation and constantly updating the personnel's position. Each complete data fusion calculation completes a positioning cycle. When a positioning cycle ends, preparations begin for the next cycle. If the mobile positioning terminal 107 is turned off or the personnel leave the tunnel, the positioning process ends. By continuously looping the above steps, the method of this invention can perform real-time dynamic positioning of personnel in tunnels, and combined with map matching, ensures that the positioning result always corresponds to the actual tunnel location, thereby significantly improving the accuracy and reliability of personnel positioning in tunnel environments.

[0069] It should be understood that the functional unit modules in the various embodiments of the present invention can be concentrated in one processing unit, or each unit module can exist physically separately, or two or more unit modules can be integrated into one unit module, and can be implemented in hardware or software.

[0070] Those skilled in the art will understand that the various embodiments disclosed above can be modified and altered in various ways without departing from the spirit of the invention. Therefore, the scope of protection of this invention should be defined by the appended claims.

[0071] It should be noted that not all steps and units in the above processes are necessary; some steps or units can be omitted as needed. The execution order of each step is not fixed and can be determined as required. The device structure described in the above embodiments can be a physical structure or a logical structure. That is, some units may be implemented by the same physical entity, or some units may be implemented by multiple physical entities, or they may be jointly implemented by certain components in multiple independent devices.

[0072] The specific embodiments described above are exemplary embodiments, but do not represent all embodiments that can be implemented or fall within the scope of the claims. The term "exemplary" as used throughout this specification means "serving as an example, instance, or illustration" and does not imply that it is "preferred" or "advantageous" compared to other embodiments. Specific details are included to provide an understanding of the described techniques. However, these techniques can be practiced without these specific details. In some instances, well-known structures and apparatuses are shown in block diagram form to avoid obscuring the concepts of the described embodiments.

[0073] The foregoing description of this disclosure is provided to enable any person skilled in the art to implement or use this disclosure. Various modifications to this disclosure will be apparent to those skilled in the art, and the general principles defined herein can be applied to other variations without departing from the scope of this disclosure. Therefore, this disclosure is not limited to the examples and designs described herein, but is consistent with the widest scope of the principles and novel features disclosed herein.

Claims

1. A real-time tunnel positioning system based on map matching, characterized in that, include: Mobile positioning terminal, several positioning anchor nodes, switch, edge gateway, positioning calculation module and management visualization platform; The plurality of positioning anchor nodes are used to be deployed in the tunnel and are communicatively connected to the edge gateway through the switch; The mobile positioning terminal includes a processor and connected to it an inertial observation module, a wireless module, and a battery; the processor calculates an inertial prior based on the observation data from the inertial observation module; the wireless module is used to interact with the plurality of positioning anchor nodes to acquire wireless observation data; the battery powers the mobile positioning terminal. The edge gateway is used to acquire the observation data of the plurality of positioning anchor nodes and mobile positioning terminals, and forward it to the positioning calculation module and the management visualization platform; The positioning calculation module includes a positioning engine and a map fingerprint database. The map fingerprint database at least pre-stores a tunnel topology composed of nodes and edges, as well as sampled wireless fingerprint statistics. The positioning engine, based on tunnel topology and wireless fingerprint statistics in the map fingerprint database, performs map matching and data fusion operations on the inertial prior and wireless observation data reported by the mobile positioning terminal. It limits the trajectory to movement only within the permitted tunnel topology boundaries, and allows switching tunnel channels only at topology nodes and when the turning angle falls within the turning gating angle threshold range. Switching tunnel channels is prohibited at non-topology nodes. The positioning results of the personnel are output and sent to the management visualization platform for real-time display.

2. The real-time tunnel positioning system based on map matching according to claim 1, characterized in that, The inertial observation module includes an accelerometer, a gyroscope, a magnetometer, and a barometer. The processor performs gait event detection and heading estimation based on the observation data from the accelerometer, gyroscope, and magnetometer to form an initial inertial prior. Then, it combines the relative altitude information observed by the barometer to correct the initial inertial prior, thus obtaining the final inertial prior.

3. The real-time tunnel positioning system based on map matching according to claim 1, characterized in that, The aforementioned positioning anchor nodes are arranged at intervals of 30 to 60 meters on straight sections of the tunnel and at intervals of 15 to 30 meters on curves or forks in the tunnel, with an installation height of 2.2 to 2.8 meters.

4. The real-time tunnel positioning system based on map matching according to claim 1, characterized in that, It also includes a clock synchronization unit, which distributes clock messages to the switch and the edge gateway. The switch forwards the clock messages to the plurality of positioning anchor nodes, thereby achieving network-wide time base alignment. The edge gateway timestamps the received observation data according to the unified time base and performs caching and forwarding.

5. The real-time tunnel positioning system based on map matching according to claim 1, characterized in that, The map fingerprint database includes a tunnel topology composed of nodes and edges, restricted areas and safety exit locations, and wireless fingerprint statistics obtained by grid sampling. Each sampling point in the wireless fingerprint statistics stores at least a list of identifiers of the positioning anchor nodes visible to that sampling point and the corresponding wireless observation data, and establishes an association relationship with the edges or nodes on the tunnel topology.

6. The real-time tunnel positioning system based on map matching according to claim 1, characterized in that, The mobile positioning terminal also includes a security chip connected to the processor, a display, and an SOS button; the security chip is used to encrypt the data sent by the wireless module; the display is used to show positioning results, navigation prompts, and alarm status; and the SOS button is used to trigger emergency event reporting.

7. The real-time tunnel positioning system based on map matching according to claim 1, characterized in that, It also includes a UPS power supply, which provides backup power to the switch and edge gateway to ensure continuous operation in the event of a power outage.

8. A real-time tunnel positioning method based on map matching, characterized in that, The method utilizes the map-matching-based real-time tunnel positioning system as described in any one of claims 1 to 7, wherein the method comprises: S1. Deploy and build the database, obtain tunnel plane and topology information and deploy positioning anchor nodes, and perform walk-through surveys in the tunnel according to the grid to collect wireless fingerprint statistics and write them into the map fingerprint database. S2. On-the-job registration: Bind the mobile positioning terminal to the personnel's identity and complete calibration and encrypted handshake; S3. Observation and acquisition: The mobile positioning terminal acquires the observation data from the inertial observation module to calculate the inertial prior, and periodically scans or accesses the positioning anchor node through the wireless module to obtain wireless observation data. The acquired inertial prior and wireless observation data are reported to the edge gateway and then forwarded to the positioning calculation module. S4. Fusion positioning: The positioning engine performs map matching and data fusion operations on the inertial prior and wireless observation data reported by the mobile positioning terminal based on the tunnel topology and wireless fingerprint statistics in the map fingerprint database. The trajectory is limited to movement within the permitted tunnel topology boundary. Switching tunnel channels is only allowed at topology nodes and when the turning angle falls within the turning gating angle threshold range. Switching tunnel channels is prohibited at non-topology nodes. The positioning result of the personnel is output. S5. Navigation guidance: The management visualization platform displays the positioning results in real time and calculates the reachable path to the nearest safe exit or designated meeting point based on the positioning results.

9. The real-time tunnel positioning method based on map matching according to claim 8, characterized in that, During the deployment and database construction process, walking survey sampling is carried out on straight sections of the tunnel at a grid spacing of 5 to 10 meters, and the grid spacing of the sampling is increased to 3 to 5 meters at curves and forks in the tunnel. The wireless fingerprint data of each sampling point is written into the map fingerprint database.

10. The real-time tunnel positioning method based on map matching according to claim 8, characterized in that, Also includes: The alarm tracking system pushes emergency events triggered by the SOS button on the mobile positioning terminal or electronic fence boundary crossing events to the management visualization platform via the edge gateway for alarm linkage. At the same time, the corresponding positioning results, event information and personnel trajectories are stored in the map fingerprint database for post-event query.

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