A route memory and reverse navigation method based on temporary WLAN

Abstract

This invention discloses a route memory and reverse navigation method based on temporary WLAN, relating to the field of positioning and navigation technology. The method includes: a positioning server receiving measurement values ​​of signals transmitted by a user terminal according to the temporary WLAN frequency from wireless access points, and fixed coordinates of multiple wireless access points; calculating the real-time coordinates of the user terminal during forward movement, ordered by time, based on the measurement values ​​and fixed coordinates, and transmitting this data to the user terminal, which then performs interpolation smoothing on the real-time coordinates to generate a continuous forward movement trajectory; responding to a reverse navigation request from the user terminal and receiving its feedback forward movement trajectory, generating reverse path data based on the forward movement trajectory; and planning a reverse navigation path based on the reverse path data, the user terminal's current coordinates, and forward movement parameters, and transmitting this path to the user terminal for visual guidance. This invention achieves route memory and accurate reverse guidance in a temporary WLAN environment.

Description

Technical Field

[0001] This invention relates to a route memory and reverse navigation method based on temporary WLAN, belonging to the field of positioning and navigation technology. Background Technology

[0002] Currently, mainstream commercial navigation technologies typically rely on the following conditions: downloading online maps and accessing cloud services through stable public communication networks (such as Wi-Fi, 4G / 5G), and planning routes using pre-stored electronic maps. However, traditional navigation technologies fail in certain special scenarios. In emergency situations such as fire rescue and earthquake disaster sites, base stations are often damaged and out of service. When rescuers enter buildings, mobile phone signals are completely lost, making it impossible to access online maps. In remote mountainous areas without network coverage, personnel also face a "disconnected" state, unable to rely on external networks for navigation information. Secondly, in unfamiliar environments without pre-stored electronic maps, traditional navigation technologies heavily rely on the mapping of "starting point-end point" on known maps. Once entering areas without map coverage, they cannot generate guiding paths, let alone plan routes in complex environments. In scenarios such as field exploration, personnel often need to safely return along the original route, but traditional navigation products cannot record routes in real time during travel, nor can they generate reverse navigation routes for backtracking in map-free environments. Once personnel lose their way in complex environments, the lack of a return route poses a serious safety hazard. Therefore, how to achieve real-time perception of personnel location, dynamic recording of travel paths, and safe return along the original route when needed in environments without public communication networks (or with poor network signals) and without pre-stored maps has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0003] The purpose of this invention is to provide a route memory and reverse navigation method based on temporary WLAN, which aims to solve the problem of safe return for personnel in environments without public communication network coverage or poor network signal and without pre-stored maps. In the scenario of pre-establishing temporary WLAN, this method calculates the forward movement trajectory in real time during forward movement. When the user initiates a reverse navigation request, the reverse navigation path is planned based on the reverse path data reconstructed from the forward trajectory, the current coordinates, and the motion parameters in the forward movement trajectory, providing a reliable guarantee for the safe return of personnel in unfamiliar environments or emergency scenarios.

[0004] To achieve the above objectives, the present invention is implemented using the following technical solution.

[0005] This invention provides a route memory and reverse navigation method based on temporary WLAN, executed by a positioning server, comprising:

[0006] Receives wireless signal measurement values ​​sent by multiple wireless access points; wherein the wireless signal is a periodic signal transmitted by the user terminal according to the frequency determined by the temporary WLAN;

[0007] Obtain the fixed coordinates of multiple wireless access points, and calculate the real-time coordinates of the user terminal in time order during forward movement based on the wireless signal measurement values;

[0008] The real-time coordinates, sorted by time, are transmitted to the user terminal so that the user terminal can perform interpolation and smoothing processing on the real-time coordinates and generate a continuous positive motion trajectory in real time.

[0009] In response to the user terminal's reverse navigation request and after receiving the forward motion trajectory it provides, reverse path data is generated based on the forward motion trajectory.

[0010] Based on the reverse path data, the user terminal's current coordinates, and the motion parameters in the forward motion trajectory, a reverse navigation path is planned to trace back from the current coordinates to the starting point of the forward motion trajectory, and the reverse navigation path is transmitted to the user terminal for visual guidance.

[0011] Optionally, the periodic signal is actively transmitted by the user terminal, or automatically transmitted by the user terminal when it detects that the signal strength of the surrounding public communication network is lower than a preset strength threshold.

[0012] The two triggering methods of the signal can ensure the continuity of the signal, providing a continuous data foundation for the generation of the forward motion trajectory and the calculation of the reverse path.

[0013] Optionally, the wireless signal measurement value is the RSSI value.

[0014] Optionally, the real-time coordinates of the user terminal during forward motion are calculated in time order, including:

[0015] Based on wireless signal measurements, the logarithmic distance path loss model is used to calculate the real-time distance between the user terminal and each wireless access point.

[0016] Based on real-time distance and fixed coordinates of wireless access points, a system of equations is constructed and solved using the principle of multi-point positioning to obtain the real-time coordinates of the user terminal.

[0017] Optionally, before transmitting the time-sorted real-time coordinates to the user terminal, an outlier removal step is included, which includes:

[0018] For the real-time coordinates at the i-th time, if the distance between the first coordinate and the second coordinate is greater than a preset distance threshold and the distance between the first time interval and the second time interval is less than a preset time threshold, then the real-time coordinates at the i-th time are determined to be an anomaly and removed.

[0019] Wherein, the first coordinate distance is the distance between the real-time coordinates of the i-th time and the real-time coordinates of the (i-1)-th time, and the second coordinate distance is the distance between the real-time coordinates of the i-th time and the real-time coordinates of the (i+1)-th time.

[0020] The first time interval is the interval between the i-th time and the (i-1)-th time, and the second time interval is the interval between the i-th time and the (i+1)-th time.

[0021] By making this judgment based on the continuity and rationality of motion, anomalies caused by instantaneous fluctuations in wireless signals can be effectively filtered out, ensuring the accuracy of the data.

[0022] Optionally, reverse path data can be generated based on the forward motion trajectory, including:

[0023] The endpoint and starting point in the forward motion trajectory are used as the starting and ending points of the reverse navigation, respectively. Based on the real-time coordinates of the forward motion trajectory, a reverse coordinate sequence is generated.

[0024] The inverse direction parameters are obtained by performing a reverse transformation on the direction parameters in the forward motion trajectory, keeping their magnitude unchanged but reversing their direction.

[0025] The reverse coordinate sequence and reverse direction parameters are combined to generate reverse path data.

[0026] The kinematic characteristics of the original path are fully preserved, avoiding path ambiguity caused by relying solely on the connection of coordinate points, and ensuring that the generated reverse path is consistent with the forward trajectory in terms of geometry, topology, and kinematics.

[0027] Optionally, the motion parameters include a velocity vector and an acceleration vector;

[0028] Plan the reverse navigation path from the current coordinates back to the starting point of the forward motion trajectory, including:

[0029] Using the current coordinates of the user terminal as the starting reference, the motion parameters in the forward motion trajectory are extracted, and combined with the reverse path data, reverse dead reckoning is performed segment by segment; wherein, in each reckoning step, the direction of the velocity vector and the acceleration vector are reversed while the magnitude remains unchanged, so as to restore the motion trajectory from the current coordinates to the starting point of the forward motion trajectory and obtain the initial reverse navigation path.

[0030] By using the dynamic parameters of forward motion for reverse calculation, the planned reverse path not only coincides with the original path in geographical coordinates, but also dynamically matches the user's current return speed and acceleration state.

[0031] Optionally, during the reverse navigation return process, the following may also be included:

[0032] In response to the blocked road information reported by the user terminal, the blocked road segment is marked in the initial reverse navigation path;

[0033] use The algorithm generates local obstacle avoidance paths that bypass congested road sections in real time, and merges these obstacle avoidance paths with the initial reverse navigation path to generate the final reverse navigation path.

[0034] Optionally, during the reverse navigation return process, the following may also be included:

[0035] Monitor the deviation of the user terminal's current coordinates from the initial reverse navigation path;

[0036] When a deviation from the preset fine-tuning range is detected, an alert signal is sent to the user terminal, and a regression path from the current coordinates to the initial reverse navigation path is generated;

[0037] The connection points between the regression path and the initial reverse navigation path are subjected to topology verification and smoothing, and then fused to generate the final reverse navigation path.

[0038] Optionally, a weighted average method can be used to fuse the local obstacle avoidance path with the initial reverse navigation path;

[0039] The initial reverse navigation path has a greater weight than the local obstacle avoidance path.

[0040] While ensuring that the basic return direction remains unchanged, flexible local path adjustments are achieved, and the reverse navigation path is given higher weight. This ensures that the merged path still guides the user back to the starting point as a whole, and will not deviate significantly from the original route due to obstacle avoidance.

[0041] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0042] This invention receives the fixed coordinates of temporarily deployed wireless access points and collects measurements of signals transmitted by user terminals at frequencies specified by the temporary WLAN. It then calculates and records the forward trajectory of the user terminals in real time. During the reverse navigation phase, it reconstructs the reverse path data based on the forward trajectory and plans the reverse navigation path by combining the current coordinates with the motion parameters in the forward trajectory. This invention eliminates the need for pre-storing the location coordinates and map data of the access points, enabling accurate route memorization and reverse guidance even in emergency environments where existing public communication networks are unavailable, providing a reliable technical means for the safe return of personnel. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the route memory and reverse navigation method based on temporary WLAN provided in an embodiment of the present invention. Detailed Implementation

[0044] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations thereof. In the absence of conflict, the embodiments of the present invention and the technical features in the embodiments can be combined with each other.

[0045] The term "and / or" simply describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. Additionally, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0046] Example 1

[0047] This embodiment uses post-disaster emergency search and rescue as a typical application scenario. In this scenario, the site typically faces extreme conditions such as damaged public network communication (WIFI, 4G / 5G) infrastructure, poor or no signal, and lack of pre-stored high-precision electronic maps. Rescue personnel carrying user terminals (beacon devices with WIFI transmission capabilities) are prone to getting disoriented when entering complex post-disaster areas, making it impossible to return to the starting point safely and efficiently, seriously threatening the lives of rescue personnel.

[0048] In response to the above problems, such as Figure 1 As shown, this embodiment provides a route memory and reverse navigation method based on temporary WLAN, achieving low-latency real-time memory of the forward travel route and complete functionality of global planning and dynamic optimization for reverse navigation. To implement this method, a temporary WLAN positioning system needs to be built first, with the following core components:

[0049] Wireless access points (APs): at least 3 units, equipped with known precise coordinates, signal transmission and reception, and data transmission capabilities, deployed in key locations (such as post-disaster site entrances and safe zones).

[0050] Location server: can be integrated into a portable computer, and has at least the ability to perform data processing, path planning, and command issuance, and is the main body for the execution of this method.

[0051] User terminal: It has functions such as WIFI beacon transmission, data reception and processing, and visualization, and has a built-in map display APP.

[0052] In the early stages of the rescue, at least three access points (APs) with known precise coordinates should be temporarily deployed at key locations such as the entrance to the disaster site and nearby safe zones. The AP coordinate accuracy must be ≤0.1m (pre-calibrated by GPS), and the AP deployment should avoid the situation where three points are collinear, so as to quickly establish a temporary WLAN positioning network.

[0053] This method is executed by a positioning server deployed at the search and rescue site. The specific steps are as follows:

[0054] S1. Receive wireless signal measurement values ​​(RSSI values) sent by multiple wireless access points.

[0055] User terminals transmit periodic signals at frequencies determined by the temporary WLAN. Multiple access points (APs) capture these signals in real time and collect the corresponding RSSI values. The positioning server continuously receives the RSSI values ​​reported by each AP.

[0056] There are two ways to transmit this periodic signal:

[0057] First, it is actively triggered. When users see that the signal strength of the existing public network (WIFI, 4G / 5G) displayed on the user terminal is lower than the strength threshold (for example, the number of signal bars is less than 2), the regular navigation service is affected, and the user terminal actively transmits periodic signals.

[0058] Second, if the user terminal detects that the signal strength of the surrounding public communication network is below -85dBm (preset weak signal threshold) for 3 consecutive seconds, it will automatically transmit periodic signals.

[0059] In this embodiment, both the transmission frequency of the periodic signal and the sampling frequency of the AP are set to 1Hz.

[0060] S2. Calculate the real-time coordinates of the user terminal during the forward motion process;

[0061] S2.1 Real-time coordinate calculation;

[0062] The positioning server obtains the fixed coordinates of all deployed access points (APs). It then calls the logarithmic distance path loss model to calculate the distance from the user terminal to each AP based on the real-time received RSSI measurements. Finally, based on the fixed coordinates of the APs and the calculated distances, it constructs a system of equations using multi-point positioning principles to solve for the two-dimensional coordinates of the user terminal at each sampling time.

[0063] Log-distance path loss model:

[0064] ;

[0065] Where A is the reference signal strength of the AP at 1 meter (in this example, A=-45dBm is factory calibrated by the AP); n is the environmental attenuation factor (dynamically adjusted according to the scenario: 2.2-2.8 for underground parking garages, 2.0-2.4 for open areas after disasters); |RSSI| is the absolute value of the signal strength measurement, in dBm.

[0066] Coordinate calculation rules: When there are 3 APs, construct a system of 3 quadratic equations and solve the two-dimensional coordinates linearly; when there are more than 3 APs, construct an overdetermined system of equations and solve the optimal estimated coordinates by the least squares method to improve positioning accuracy.

[0067] Taking 3 access points as an example, let the coordinates of the access points be respectively The distances from the user terminals to each AP, calculated by the server, are as follows: ;

[0068] Specific user terminal coordinates ( The solution process is as follows:

[0069] ;

[0070] ;

[0071] ;

[0072] Linearization yields a linearized system of equations:

[0073] ;

[0074] ;

[0075] make:

[0076] ;

[0077] ;

[0078] in, , , , , , It has no specific engineering meaning; it is only presented to explain the calculation process.

[0079] The system of equations then simplifies to:

[0080] ;

[0081] ;

[0082] make:

[0083] ;

[0084] Solving for:

[0085] ;

[0086] As rescuers move, the positioning server continuously calculates the coordinates at each moment using a sampling frequency of 1Hz, generating real-time coordinate data sorted by time.

[0087] S2.2, Anomaly removal preprocessing;

[0088] Real-time coordinate data sorted by time may contain abrupt changes due to instantaneous signal fluctuations. The server implements the following outlier removal logic, ensuring that only valid coordinates that have passed verification are included in subsequent transmission stages:

[0089] For each coordinate Calculate its relationship with the points before and after it. and Spatial distance, if and and The distances to all points are greater than a preset distance threshold (3m in this embodiment), and the corresponding time intervals are all less than a preset time threshold (0.5s in this embodiment). This means that the point... If a jump occurs, it is identified as an anomaly and removed.

[0090] Since the removal of outliers requires waiting for the coordinates obtained from the next sampling to be verified, there is a 1Hz delay in the effective coordinates transmitted to the user terminal. This delay is completely acceptable for post-disaster search and rescue and ensures the accuracy of the forward trajectory data used for reverse navigation from the source, which is in line with the purpose of reverse navigation safety.

[0091] S3. Transmit the real-time coordinates sorted by time to the user terminal so that the user terminal can perform interpolation and smoothing processing on the real-time coordinates and generate a continuous positive motion trajectory in real time.

[0092] The positioning server transmits the real-time coordinates to the user terminal and uses a linear interpolation algorithm for smoothing to generate and display a continuous positive motion trajectory.

[0093] Set adjacent sampling points and If the sampling frequency is 1Hz and the interpolation frequency is 10Hz, then the formula for calculating the interpolation point coordinates is:

[0094] , ;

[0095] in, The original sampling point number. It is the index of the interpolation point (i=1,2...9). This represents the sampling time interval.

[0096] The 1Hz sampling frequency is logically adapted to the 10Hz interpolation frequency to solve the problems of trajectory breakpoints and polylines, generating a continuous and smooth positive motion trajectory between adjacent points and displaying it in real time on the map display APP on the user terminal. Thus, the recording and generation of the positive trajectory is completed.

[0097] S4. In response to the user terminal's reverse navigation request and after receiving the forward motion trajectory it provides, generate reverse path data based on the forward motion trajectory.

[0098] S4.1 Reverse reconstruction of coordinate sequence;

[0099] The positioning server extracts the valid real-time coordinate sequence corresponding to the forward motion trajectory, sets the end point of the forward motion trajectory as the starting point of the reverse navigation, and sets the starting point of the forward trajectory as the end point of the reverse navigation. The valid real-time coordinate sequence of the forward trajectory is arranged in reverse time order to generate the reverse coordinate sequence.

[0100] S4.2, Reverse conversion of direction parameters;

[0101] The positioning server extracts the directional parameters (device orientation angle) recorded during forward movement. The AP signal propagation direction vector Z is used to perform an inverse transformation on each direction parameter, keeping the magnitude unchanged but reversing the direction: direction angle. AP signal vector ).

[0102] Finally, the reverse coordinate sequence and the reverse direction parameters are combined to generate complete reverse path data.

[0103] For example: during forward motion, the travel direction angle recorded by the user terminal at a certain sampling moment. =225° (southwest direction, deeper into the disaster area), AP signal propagation direction vector = (2, 3); After reverse conversion, the direction angle (Northeast direction, returning to the entrance), signal vector = (-2, -3), which is opposite in direction and the same in magnitude as the original vector, ensuring that the direction guidance of reverse navigation corresponds completely to the forward travel direction.

[0104] S5. Based on the reverse path data, the current coordinates of the user terminal, and the motion parameters in the forward motion trajectory, plan a reverse navigation path from the current coordinates back to the starting point of the forward motion trajectory, and transmit the reverse navigation path to the user terminal for visual guidance.

[0105] S5.1 Generation of the initial reverse navigation path based on reverse dead reckoning;

[0106] The positioning server extracts the motion parameters recorded in the forward motion trajectory (including the velocity vector at each moment). acceleration vector Starting from the current coordinates of the user terminal, and combining the reverse path data generated by S4, reverse dead reckoning is performed segment by segment.

[0107] In each calculation step, the directions of the velocity and acceleration vectors are reversed while their magnitudes remain unchanged. By recursively calculating backwards, the complete motion process from the current coordinates back to the starting point of the forward trajectory is reconstructed, generating the initial reverse navigation path.

[0108] By using the dynamic parameters of forward motion for reverse calculation, the planned reverse path not only coincides with the original path in geographical coordinates, but also dynamically matches the user's current return speed and acceleration state.

[0109] S5.2 Path optimization for dynamic obstacle avoidance and deviation correction;

[0110] During the reverse return process, the positioning server supports on-site information reporting and has dynamic environmental awareness and path adaptive adjustment capabilities. These two functions can be executed independently or in combination to calculate the optimal return path, specifically including:

[0111] Obstacle Avoidance: If rescue personnel encounter secondary collapses, flooding, or other obstructions on the original route during their return journey (i.e., they cannot proceed along the original path), they can report the obstruction information (coordinate range) via their user terminal. Upon receiving the report, the positioning server marks the obstructed section in the initial reverse navigation path and immediately uses the A* algorithm to generate a local obstacle avoidance path that bypasses the obstruction. Subsequently, the obstacle avoidance path is merged with the initial reverse navigation path to generate the final reverse navigation path. In this embodiment, a weighted average method is used for merging, and the weight of the initial reverse navigation path is greater than the weight of the local obstacle avoidance path (e.g., initial reverse navigation path weight 0.6, obstacle avoidance path weight 0.4) to maintain overall direction consistency with the original path.

[0112] Route deviation correction: The positioning server continuously monitors the deviation between the user terminal's current coordinates and the initial reverse navigation path. When a deviation of ≤0.5m (preset fine-tuning range) is detected, an alert signal (such as vibration alert) is sent to the user terminal, and a local regression path is immediately generated to return to the initial reverse navigation path from the current coordinates. Topology verification (to ensure the regression path is feasible) and smoothing (to ensure the regression path is visually smooth) are performed on the connection points between the regression path and the initial reverse navigation path. The two are then merged and updated to obtain the final reverse navigation path, which is sent to the user terminal to guide the user to continue returning.

[0113] The positioning server transmits the final reverse navigation path to the user terminal in real time. The map display app on the user terminal provides visual guidance through arrow indicators and track highlighting, guiding rescuers to safely and accurately return to the starting point along the planned path.

[0114] In summary, this invention receives the fixed coordinates of temporarily deployed wireless access points and collects measurements of signals transmitted by user terminals at frequencies specified by the temporary WLAN. It then calculates and records the forward trajectory of the user terminals in real time. During the reverse navigation phase, it reconstructs the reverse path data based on the forward trajectory and plans the reverse navigation path by combining the current coordinates with the motion parameters in the forward trajectory. Furthermore, during the reverse return process, it possesses dynamic environmental awareness and path adaptive adjustment capabilities, ensuring the safe return of personnel. This invention does not require pre-storing the location coordinates and map data of access points, enabling accurate route memorization and reverse guidance even in emergency environments where existing public communication networks are unavailable, providing a reliable technical means for the safe return of personnel.

[0115] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0116] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A route memory and reverse navigation method based on temporary WLAN, characterized in that, Performed by the location server, including: Receives wireless signal measurement values ​​sent by multiple wireless access points; wherein the wireless signal is a periodic signal transmitted by the user terminal according to the frequency determined by the temporary WLAN; Obtain the fixed coordinates of multiple wireless access points, and calculate the real-time coordinates of the user terminal in time order during forward movement based on the wireless signal measurement values; The real-time coordinates, sorted by time, are transmitted to the user terminal so that the user terminal can perform interpolation and smoothing on the real-time coordinates and generate a continuous positive motion trajectory in real time. In response to the user terminal's reverse navigation request and after receiving the forward motion trajectory from it, reverse path data is generated based on the forward motion trajectory. Based on the reverse path data, the user terminal's current coordinates, and the motion parameters in the forward motion trajectory, a reverse navigation path is planned to trace back from the current coordinates to the starting point of the forward motion trajectory, and the reverse navigation path is transmitted to the user terminal for visual guidance.

2. The route memory and reverse navigation method based on temporary WLAN according to claim 1, characterized in that, The periodic signal is actively transmitted by the user terminal, or automatically transmitted by the user terminal when it detects that the signal strength of the surrounding public communication network is lower than a preset strength threshold.

3. The route memory and reverse navigation method based on temporary WLAN according to claim 1, characterized in that, The wireless signal measurement value is the RSSI value.

4. The route memory and reverse navigation method based on temporary WLAN according to claim 1, characterized in that, Calculate the real-time coordinates of the user terminal sorted by time during its forward motion, including: Based on wireless signal measurements, the logarithmic distance path loss model is used to calculate the real-time distance between the user terminal and each wireless access point. Based on real-time distance and fixed coordinates of wireless access points, a system of equations is constructed and solved using the principle of multi-point positioning to obtain the real-time coordinates of the user terminal.

5. The route memory and reverse navigation method based on temporary WLAN according to claim 1, characterized in that, Before transmitting the time-sorted real-time coordinates to the user terminal, the process includes an outlier removal step, which includes: For the real-time coordinates at the i-th time, if the distance between the first coordinate and the second coordinate is greater than a preset distance threshold and the distance between the first time interval and the second time interval is less than a preset time threshold, then the real-time coordinates at the i-th time are determined to be an anomaly and removed. Wherein, the first coordinate distance is the distance between the real-time coordinates of the i-th time and the real-time coordinates of the (i-1)-th time, and the second coordinate distance is the distance between the real-time coordinates of the i-th time and the real-time coordinates of the (i+1)-th time. The first time interval is the interval between the i-th time and the (i-1)-th time, and the second time interval is the interval between the i-th time and the (i+1)-th time.

6. The route memory and reverse navigation method based on temporary WLAN according to claim 1, characterized in that, Generate reverse path data based on the forward motion trajectory, including: The endpoint and starting point in the forward motion trajectory are used as the starting and ending points of the reverse navigation, respectively. Based on the real-time coordinates of the forward motion trajectory, a reverse coordinate sequence is generated. The inverse direction parameters are obtained by performing a reverse transformation on the direction parameters in the forward motion trajectory, keeping their magnitude unchanged but reversing their direction. The reverse coordinate sequence and reverse direction parameters are combined to generate reverse path data.

7. The route memory and reverse navigation method based on temporary WLAN according to claim 1, characterized in that, The motion parameters include velocity vector and acceleration vector; Plan the reverse navigation path from the current coordinates back to the starting point of the forward motion trajectory, including: Using the current coordinates of the user terminal as the starting reference, the motion parameters in the forward motion trajectory are extracted, and combined with the reverse path data, reverse dead reckoning is performed segment by segment; wherein, in each reckoning step, the direction of the velocity vector and the acceleration vector are reversed while the magnitude remains unchanged, so as to restore the motion trajectory from the current coordinates to the starting point of the forward motion trajectory and obtain the initial reverse navigation path.

8. The route memory and reverse navigation method based on temporary WLAN according to claim 7, characterized in that, The reverse navigation return process also includes: In response to the blocked road information reported by the user terminal, the blocked road segment is marked in the initial reverse navigation path; use The algorithm generates local obstacle avoidance paths that bypass congested road sections in real time, and merges these paths with the initial reverse navigation path to generate the final reverse navigation path.

9. The route memory and reverse navigation method based on temporary WLAN according to claim 7, characterized in that, The reverse navigation return process also includes: Monitor the deviation of the user terminal's current coordinates from the initial reverse navigation path; When a deviation from the preset fine-tuning range is detected, an alert signal is sent to the user terminal, and a regression path from the current coordinates to the initial reverse navigation path is generated; The connection points between the regression path and the initial reverse navigation path are subjected to topology verification and smoothing processing, and then fused to generate the final reverse navigation path.

10. The route memory and reverse navigation method based on temporary WLAN according to claim 8, characterized in that, A weighted average method is used to fuse the local obstacle avoidance path with the initial reverse navigation path; The weight of the initial reverse navigation path is greater than the weight of the local obstacle avoidance path.

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