ELoran receiver system delay calibration method and system based on multipoint ASF measurement
By constructing a joint inversion model using multi-point ASF measurements and theoretical values, the problem of inaccurate ASF measurement results in the eLoran system was solved, achieving high-precision system delay calibration and improving eLoran timing accuracy.
Patent Information
- Application Number
- CN202512009890.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-29
- Publication Date
- 2026-03-06
AI Technical Summary
The timing accuracy of the existing eLoran system is affected by the secondary delay ASF added by the propagation path, which is difficult to predict accurately through theoretical models, resulting in inaccurate ASF measurement results. Existing calibration methods cannot achieve high-precision system delay calibration.
A multi-point ASF measurement method is adopted, and a joint inversion model is constructed by combining measured ASF data with theoretical values. The system delay is solved by combining optimization algorithms, thereby decoupling the measured ASF values from the receiver system delay and achieving high-precision system delay calibration.
It significantly improves the accuracy of system delay calibration and the reliability of ASF measurement, eliminates the influence of model error in traditional methods, and improves eLoran timing performance.
Smart Images
Figure CN121613481A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of land-based longwave timing and navigation, specifically to a delay calibration method and system for an eLoran receiver system based on multi-point ASF measurements. Background Technology
[0002] With the increasing application of Global Navigation Satellite System (GNSS) in various key fields, its susceptibility to interference, susceptibility to deception, and potential failure in complex electromagnetic environments have become increasingly prominent. As a land-based long-wave timing and navigation system, eLoran has advantages such as long transmission distance, high signal stability, strong diffraction capability, and strong anti-interference capability, making it an important component in building a highly reliable integrated positioning, navigation, and timing (PNT) system.
[0003] However, the timing accuracy of the eLoran system still lags behind that of the Global Positioning System (GPS). Its timing accuracy is primarily affected by the Additional Secondary Factor (ASF) along the propagation path. Due to the topographical variations along the propagation path and the uncertainties in parameters such as earth conductivity and atmospheric refractive index, the ASF is difficult to predict accurately using theoretical models. Therefore, experimental measurements have become the main method for obtaining high-precision ASF data. The accuracy of ASF measurements depends on the accurate calibration of the receiver system delay; if there is a deviation in the system delay estimation, it will be directly superimposed on the ASF measurement results, affecting the accuracy of subsequent ASF spatiotemporal corrections. Therefore, achieving high-precision system delay calibration is a prerequisite for obtaining reliable ASF measurements and improving eLoran timing performance.
[0004] eLoran receiver system delay refers to the total time delay experienced by the signal from its arrival at the receiving antenna to the triggering of timing. This delay originates from various components including the receiving antenna, feeder (cable), RF analog circuitry, and signal processing algorithms. Existing system delay calibration methods mainly include those based on eLoran signal analog sources and those based on actual eLoran signals. The former can typically assess the receiver's internal delay relatively accurately, but it cannot adequately represent the delay contributions of the antenna and feeder under real far-field conditions. The latter comprehensively considers the delay of each component, but relies on theoretical ASF values for calculation, making it susceptible to model errors. Therefore, neither method can achieve high-precision, engineered system delay calibration. Summary of the Invention
[0005] To address the problems mentioned in the prior art, this invention proposes an eLoran receiver system delay calibration method and system based on multi-point ASF measurements. This method relies on ASF space-time separation, constructs a joint inversion model of system delay and ground conductivity through multi-point ASF measured data and ASF theoretical values, achieves high-precision calibration of the reference receiver system delay, and further forms a rapid calibration process applicable to multiple devices to solve the problem of difficulty in decoupling the ASF measured values from the receiver system delay.
[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention proposes a delay calibration method for an eLoran receiver system based on multi-point ASF measurements, comprising the following steps: S1. Establish a benchmark point within the calibration area, and use a pre-built ASF monitoring system to continuously monitor the benchmark point and obtain the ASF time component of the benchmark point. S2. Select multiple measurement points within the calibration area, use a reference receiver to acquire the measured ASF values of each measurement point, and perform space-time separation on the measured ASF values of each measurement point based on the ASF time component of the reference point to obtain the ASF spatial component of each measurement point. S3. Based on the ASF spatial components and theoretical ASF values of each measurement point, a joint inversion model is constructed with the system delay and the segmented ground conductivity of the propagation path as the objectives. The system delay of the reference receiver is obtained by solving the model through an optimization algorithm. S4. Select a fixed calibration point and use the ASF monitoring system to monitor the fixed calibration point to obtain the ASF time component of the fixed calibration point; place the reference receiver that has completed the system delay calibration at the fixed calibration point for short-time measurement, and combine the ASF time component of the corresponding time period at the fixed calibration point to determine the ASF spatial reference value of the fixed calibration point. S5. Place the receiver to be calibrated at a fixed calibration point and perform short-time ASF measurement. Based on the measurement period, obtain the corresponding ASF time component from the fixed calibration point and calculate the system delay of the receiver to be calibrated by combining the ASF spatial reference value of the fixed calibration point.
[0007] As a further improvement of the present invention, step S1 involves using a pre-built ASF monitoring system to continuously monitor a reference point and obtain the ASF time component of the reference point, including: Select multi-day monitoring data with stable meteorological conditions, extract ASF measurement values for fixed time periods each day and calculate the mean, and average the mean results of multiple days to obtain the ASF spatial reference value of the reference point. The ASF time component of the reference point is obtained by subtracting the corresponding ASF spatial reference value from the measured ASF value of the reference point.
[0008] As a further improvement of the present invention, in step S2, the measured ASF values of each measurement point are separated into spatial and temporal components based on the ASF time component of the reference point to obtain the ASF spatial components of each measurement point, including: Extract the ASF time components of the reference point corresponding to the observation period of the measurement point, and take the average value as the ASF time component of the measurement point; Subtract the corresponding ASF time component from the measured ASF value of the measurement point to obtain the ASF spatial component of that measurement point.
[0009] As a further improvement to the present invention, the objective function of the joint inversion model in S3 is shown in the following equation:
[0010] In the formula: For the first ASF spatial components at each measurement point (including system delay); For the first Theoretical ASF values for each measurement point; Indicates the first The parameters of the propagation path model for each measurement point, where This represents the distribution of earth conductivity along the path. Indicates the first The distance between each segment of the measurement point.
[0011] As a further improvement of the present invention, the objective function of the joint inversion model in S3 is solved by an optimization algorithm to obtain the system delay of the reference receiver, including: S31. Combining the geodetic conductivity map and the topographic data of the experimental area, the propagation path is divided into N segments, and the conductivity range of each segment is set; based on the distribution of the theoretical ASF values in the experimental area, the range of system delay values is preliminarily estimated. S32. Within the parameter constraints, a preset number of search proxy locations are randomly initialized, as shown in the following expression:
[0012] In the formula: It is a random number in the range [0,1]. For the first The lower bound of the dimension parameter, ; For the first The upper limit of the dimension parameter, ; S33. Calculate the fitness of all search agents according to the joint inversion objective function. The position of the search agent with the smallest fitness is the current optimal solution. S34. Calculate the energy coefficient. If the energy coefficient is greater than 1, the search agent updates its position through long-distance migration or burrowing. If the energy coefficient is less than or equal to 1, the search agent updates its position through foraging or avoiding predators, and re-determines the current optimal solution. S35. Repeat S34 until the maximum number of iterations is reached, and output the current optimal position, which is the system delay of the reference receiver.
[0013] As a further improvement to the present invention, the specific process of S4 is as follows: The measured ASF value at the fixed calibration point is obtained by measuring with a reference receiver at the fixed calibration point. Obtain the ASF time components from the reference point for the corresponding measurement period; Subtract the ASF time component of the reference point from the measured ASF value at the fixed calibration point to obtain the ASF spatial reference value at the fixed calibration point.
[0014] As a further improvement of the present invention, the expression for calculating the system delay of the receiver to be calibrated in step S5 is as follows:
[0015] In the formula: The ASF measurement value for the receiver to be calibrated includes system delay; The ASF time component is the fixed calibration point corresponding to the measurement period; Spatial reference values for fixed calibration points; This is due to system latency.
[0016] This invention proposes an eLoran receiver system delay calibration system based on multi-point ASF measurement, used to implement the aforementioned method, comprising: The first acquisition module is used to establish a reference point within the calibration area, and to continuously monitor the reference point using a pre-built ASF monitoring system to acquire the ASF time component of the reference point. The second acquisition module is used to select multiple measurement points in the calibration area, acquire the ASF measured value of each measurement point using a reference receiver, and perform spatiotemporal separation on the ASF measured value of each measurement point based on the ASF time component of the reference point to obtain the ASF spatial component of each measurement point. The solution module constructs a joint inversion model based on the ASF spatial components and theoretical ASF values of each measurement point, with the system delay and the segmented ground conductivity of the propagation path as the objectives. The system delay of the reference receiver is obtained by solving the model through an optimization algorithm. The measurement module is used to select a fixed calibration point and obtain the ASF time component of the fixed calibration point; the reference receiver that has completed the system delay calibration is placed at the fixed calibration point for short-time measurement, and the ASF spatial reference value of the fixed calibration point is determined by combining the ASF time component of the corresponding time period of the fixed calibration point. The output module is used to place the receiver to be calibrated at a fixed calibration point for short-term ASF measurement, obtain the corresponding ASF time component from the fixed calibration point based on the measurement period, and calculate the system delay of the receiver to be calibrated by combining the ASF spatial reference value of the fixed calibration point.
[0017] This invention proposes an eLoran receiver system delay calibration device based on multi-point ASF measurement, comprising a processor and a memory, wherein the processor executes a computer program stored in the memory to implement the eLoran receiver system delay calibration method based on multi-point ASF measurement as described above.
[0018] This invention proposes a computer-readable storage medium for storing a computer program, wherein the computer program, when executed by a processor, implements the eLoran receiver system delay calibration method based on multi-point ASF measurement as described above.
[0019] Compared with the prior art, the present invention achieves the following technical effects: Traditional calibration methods based on eLoran signal analog sources input analog signals to the receiver via direct connection to RF cables or near-field radiation, typically only evaluating the receiver's internal delay and ignoring the influence of factors such as the receiving antenna and feeder (cable). This leads to the introduction of delays from these external components into the ASF measurement results, causing systematic bias. Therefore, the calibration method proposed in this invention comprehensively considers the overall delay characteristics of each component, including the receiving antenna, feeder, RF analog circuit, and signal processing algorithm, and can effectively eliminate the influence of system delays on the ASF measurement results.
[0020] This invention constructs a joint inversion function of system delay and path ground conductivity by constraining multi-point ASF measured values and ASF theoretical values, thereby achieving effective separation of the coupling term between system delay and ASF measured values. This significantly improves the accuracy of system delay calibration and the reliability of ASF measurement, and solves the problem that traditional calibration methods based on actual eLoran signals rely on theoretical calculations of ASF, inevitably mixing model errors into the estimated system delay. Attached Figure Description
[0021] Figure 1 This is a schematic diagram of the overall process of the present invention; Figure 2 This is a schematic diagram of the ASF monitoring system of the present invention; Figure 3This is a schematic diagram of the ASF external measurement system of the present invention; Figure 4 This is a schematic diagram of the delay inversion process of the system of the present invention; Figure 5 This is a schematic diagram of the propagation path model of the present invention; Figure 6 This is a schematic diagram showing the distribution of the delay calibration area and measurement points in the system of the present invention; Figure 7 This is a schematic diagram of the ASF measurement system built at the reference point according to the present invention; Figure 8 This is a schematic diagram of the measured ASF values (including system delay) at the reference point of this invention; Figure 9 This is a schematic diagram of the ASF time components at the reference point of this invention; Figure 10 This is a schematic diagram of the ASF measurement results of the reference receiver at XUT in this invention; Figure 11 This is a schematic diagram of the ASF measurement results of the receiver to be calibrated in this invention at XUT. Detailed Implementation
[0022] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.
[0023] See Figure 1 This embodiment proposes a delay calibration method for an eLoran receiver system based on multi-point ASF measurement, including the following steps: S1. Establish a benchmark point within the calibration area, and use a pre-built ASF monitoring system to continuously monitor the benchmark point and obtain the ASF time component of the benchmark point. S2. Select multiple measurement points within the calibration area, use a reference receiver to acquire the measured ASF values of each measurement point, and perform space-time separation on the measured ASF values of each measurement point based on the ASF time component of the reference point to obtain the ASF spatial component of each measurement point. S3. Based on the ASF spatial components and theoretical ASF values of each measurement point, a joint inversion model is constructed with the system delay and the segmented ground conductivity of the propagation path as the objectives. The system delay of the reference receiver is obtained by solving the model through an optimization algorithm. S4. Select a fixed calibration point and use the ASF monitoring system to monitor the fixed calibration point to obtain the ASF time component of the fixed calibration point; place the reference receiver that has completed the system delay calibration at the fixed calibration point for short-time measurement, and combine the ASF time component of the corresponding time period at the fixed calibration point to determine the ASF spatial reference value of the fixed calibration point. S5. Place the receiver to be calibrated at a fixed calibration point and perform short-time ASF measurement. Based on the measurement period, obtain the corresponding ASF time component from the fixed calibration point and calculate the system delay of the receiver to be calibrated by combining the ASF spatial reference value of the fixed calibration point.
[0024] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments: Step 1: Select an area with relatively flat terrain, uniform geological type, moderate propagation distance, and open receiving environment as the system delay calibration area, set up a reference point within this area, and build an ASF monitoring system; Figure 2 As shown, the ASF monitoring system in this embodiment includes an eLoran receiver and antenna with a counting module, a calibrated GPS receiver and antenna, and an industrial control computer. During the experiment, this system continuously collects ASF data from the reference point, providing a time reference for subsequent ASF space-time separation. The eLoran receiver used in this stage does not require system delay calibration.
[0025] Step 2: Select an eLoran receiver as the reference receiver configuration as follows Figure 3 The ASF external measurement system is shown. Using this system, multiple measurement points are sequentially selected within the calibration area to conduct ASF measurements. After the measurements stabilize, ASF data is continuously collected for 10–15 minutes at each measurement point, and the average value is taken as the measured ASF value for that point. Subsequently, using the ASF time component provided by the ASF monitoring system, the measured ASF values at each measurement point are separated into spatial and temporal components. The specific steps are as follows: (1) Determine the ASF spatial reference value (including system delay) of the reference point. Selecting areas with stable meteorological conditions Daily monitoring data is used to extract ASF measurements during fixed time periods (e.g., 5:00-6:00 AM, when data fluctuations are small) and calculate their average. Then, the... The average of the results over the days yields the ASF spatial reference value for the reference point. As shown in equation (1).
[0026] (1) In the formula: For the first The mean of ASF over a fixed period of time.
[0027] (2) Calculate the ASF time component of the reference point The ASF time component of a reference point can be obtained by subtracting its spatial reference value from the measured ASF value at the reference point. As shown in equation (2).
[0028] (2) In the formula: The measured ASF value is used as the reference point.
[0029] (3) Determine the ASF time component of the measurement point Extract the ASF time components of the reference point corresponding to the observation period of the measurement point, and take their mean as the ASF time component of the measurement point. .
[0030] (4) Calculate the ASF spatial components of the measurement points
[0031] The spatial component of the measurement point ASF can be obtained by subtracting its time component from the measured value of the measurement point ASF, as shown in equation (3).
[0032] (3) In the formula: The measured ASF value is the value at the measurement point.
[0033] Step 3: Select A number of measurement points are used to construct a system delay. Earth conductivity segmented by propagation path The joint inversion objective function for optimizing the variables is shown in equation (4). The goal of the inversion is to find the optimal parameters. Minimize the objective function in equation (4) to make the ASF spatial components at each measurement point as close as possible to the theoretical value, thereby obtaining the optimal system delay.
[0034] (4) in, For the first ASF spatial components at each measurement point (including system delay); The first equation calculated using the Integral Equation (IE) method is... Theoretical ASF values for each measurement point; Indicates the first The parameters of the propagation path model for each measurement point, where This represents the distribution of earth conductivity along the path. Indicates the first The distance between each segment of the measurement point.
[0035] Subsequently, the objective function is optimized using the Artificial Lemming Algorithm (ALA) to determine the system delay of the reference receiver. The inversion process is as follows: Figure 4 As shown. The specific method is as follows: (1) Parameter setting First, combining the China geoelectric conductivity map with the topographic data of the experimental area, the propagation path was divided into... Section, such as Figure 5 As shown, the conductivity range for each segment is set. Secondly, based on the distribution of the theoretical ASF values in the experimental region, the range of system delay values is initially estimated, providing parameter constraints for subsequent inversion.
[0036] (2) Initialization Assume the number of search agents (i.e., lemmings) is Within the parameter constraints The location of each search agent is randomly initialized.
[0037] (5) in, It is a random number in the range [0,1]. For the first The lower bound of the dimension parameter, ; For the first The upper limit of the dimension parameter, .
[0038] (3) Calculation of individual fitness The fitness of all search agents is calculated according to equation (4), and the position of the search agent with the lowest fitness is the current optimal solution. .
[0039] (4) Individual location update In each iteration, the energy coefficient is first calculated according to equation (6). ,like ALA enters the exploration phase through long-distance migration or burrowing; if ALA enters the mining phase by foraging or avoiding predators. All search agents update their locations based on this principle and determine the current optimal solution.
[0040] (6) in, This indicates the maximum number of iterations.
[0041] (5) Convergence judgment and output of the optimal solution If the maximum number of iterations is reached, repeat step (4); when the number of iterations reaches the set upper limit, output the current optimal position. This allows us to obtain the optimal system delay for the reference receiver.
[0042] Step 4: Within the calibration area, select a location with a stable electromagnetic environment, no obstructions, and a long-term power supply as a fixed calibration point, and set up an ASF measurement system to continuously acquire the ASF time component at that point. The eLoran receiver used also does not require calibration.
[0043] An ASF measurement system is constructed using a calibrated reference receiver. Short-time ASF measurements are performed at the calibration point. Using the ASF space-time separation method from step 2, combined with the ASF time component of the fixed calibration point for the corresponding time period, the ASF spatial component of that fixed calibration point is calculated and used as the ASF spatial reference value for that fixed calibration point. This ASF spatial reference value serves as a unified benchmark for the delay calibration of other receiver systems.
[0044] Step 5: Assemble the eLoran receiver to be calibrated into an ASF measurement system, place it at the fixed calibration point described in Step 4 for short-time ASF measurement, and extract the ASF time component of the fixed calibration point for the corresponding time period. Combined with the ASF spatial reference value obtained in Step 4, the system delay of the receiver can be calculated using Equation (7), thereby achieving fast and standardized system delay calibration.
[0045] (7) in, For ASF measurements that include system delay, The time component of the ASF at the fixed calibration point during the measurement period; This is the spatial reference value for the calibration point.
[0046] This embodiment provides an application of the method of the present invention for system delay calibration as follows: Step 1: Select a local area in the southern part of Xi'an as the system delay calibration test area, such as... Figure 6 As shown. Xi'an University of Technology (XUT) was selected as the reference point, and an ASF monitoring system was built there, as follows. Figure 7 As shown. This area is located in the Guanzhong Plain, approximately 90–105 km from the Pucheng launch site. The propagation path has a uniform geological type, generally flat terrain, moderate path length, and a relatively open receiving environment. An ASF measurement system was deployed in this area to continuously collect ASF data within the experimental section, such as... Figure 8 As shown.
[0047] Step 2: Select an eLoran receiver to form an ASF measurement system. In May 2022, ASF measurements were conducted in the southern area of Xi'an City. ASF data were obtained from 23 points, and the distribution of the measurement points is shown in Figure 5.
[0048] Space-time separation was performed on the ASF data from 23 measurement points: (1) Select the ASF data of the benchmark point during 3 days of clear weather from 5:00 to 6:00. The mean values are 78.617μs, 78.645μs and 78.630μs respectively. The ASF spatial benchmark value of the benchmark point is 78.631μs.
[0049] (2) The time component of the reference point is as follows Figure 9 As shown.
[0050] (3) The corresponding ASF time component of the measurement period at measurement point 1 is +0.062μs.
[0051] (4) The measured ASF value at measurement point 1 is 79.825 μs, so its spatial component is 79.763 μs. The spatial components of the other measurement points can be obtained in the same way.
[0052] Step 3: Select 6 measurement points (i.e. Figure 5 The inversion was performed on the yellow dots in the diagram. The ASF spatial components at each measurement point were 79.763 μs, 79.776 μs, 79.747 μs, 79.786 μs, and 79.744 μs, respectively. The propagation path conductivity was treated as a single segment, and the objective function was... (8) Based on the topographic features and geomorphic features of the propagation path in the experimental area, as well as the earth conductivity map, the conductivity value for this path was set to range from 0.005 to 0.025 S / m. Simultaneously, the system delay range was set to 78-80 μs based on the theoretical ASF values at the measurement points. During the optimization process, the population size and maximum number of iterations of the ALA algorithm were both set to 200, and the algorithm was run independently 10 times under the same parameter conditions to ensure the stability of the results.
[0053] Under the above optimization settings, the minimum value of the objective function In multiple independent runs, the optimal solution was stably reproduced: the system delay of the reference receiver was 79.046 μs, and the propagation path conductivity was 0.0098 S / m.
[0054] Step 4: Given that the XUT is open and unobstructed, has a stable electromagnetic environment, and is easy to operate and maintain for a long time, the XUT is still selected as a fixed calibration point, and an ASF measurement system is used for long-term monitoring to continuously acquire the ASF time component at this point. The ASF measurement system, composed of a calibrated reference receiver, measured the actual ASF value of the XUT to be 0.710 μs. Figure 10 As shown. Combined with concurrent monitoring data, the time-varying component of the measurement period is +0.014 μs. Based on this, the ASF spatial component of the XUT can be calculated to be 0.696 μs, which is the ASF spatial reference value at the calibration point. It is 0.696 μs.
[0055] Step 5: Select an uncalibrated eLoran receiver to assemble an ASF monitoring system, conduct short-term observations at XUT, and obtain the measured ASF value including system delay. It is 79.412 μs, such as Figure 11 As shown. Combined with concurrent monitoring data, the time-varying components of ASF during the measurement period. If the delay is -0.014μs, then the system delay of this receiver is... It is 78.730 μs.
[0056] Based on the same inventive concept, this embodiment of the invention also provides an eLoran receiver system delay calibration system based on multi-point ASF measurement. Since the principle of solving the problem by this eLoran receiver system delay calibration system based on multi-point ASF measurement is similar to the aforementioned eLoran receiver system delay calibration method based on multi-point ASF measurement, the implementation of this eLoran receiver system delay calibration system based on multi-point ASF measurement can refer to the implementation of the eLoran receiver system delay calibration method based on multi-point ASF measurement, and the repeated parts will not be described again.
[0057] In specific implementation, the eLoran receiver system delay calibration system based on multi-point ASF measurement provided in this embodiment of the invention specifically includes: The first acquisition module is used to establish a reference point within the calibration area, and to continuously monitor the reference point using a pre-built ASF monitoring system to acquire the ASF time component of the reference point. The second acquisition module is used to select multiple measurement points in the calibration area, acquire the ASF measured value of each measurement point using a reference receiver, and perform spatiotemporal separation on the ASF measured value of each measurement point based on the ASF time component of the reference point to obtain the ASF spatial component of each measurement point. The solution module constructs a joint inversion model based on the ASF spatial components and theoretical ASF values of each measurement point, with the system delay and the segmented ground conductivity of the propagation path as the objectives. The system delay of the reference receiver is obtained by solving the model through an optimization algorithm. The measurement module is used to select a fixed calibration point and obtain the ASF time component of the fixed calibration point; the reference receiver that has completed the system delay calibration is placed at the fixed calibration point for short-time measurement, and the ASF spatial reference value of the fixed calibration point is determined by combining the ASF time component of the corresponding time period of the fixed calibration point. The output module is used to place the receiver to be calibrated at a fixed calibration point for short-term ASF measurement, obtain the corresponding ASF time component from the fixed calibration point based on the measurement period, and calculate the system delay of the receiver to be calibrated by combining the ASF spatial reference value of the fixed calibration point.
[0058] Accordingly, this embodiment of the invention also provides an eLoran receiver system delay calibration device based on multi-point ASF measurement, including a processor and a memory, wherein the processor executes a computer program stored in the memory to implement the eLoran receiver system delay calibration method based on multi-point ASF measurement as provided in this embodiment of the invention.
[0059] For a more detailed explanation of the above method, please refer to the relevant content disclosed in the foregoing embodiments, which will not be repeated here.
[0060] Accordingly, embodiments of the present invention also provide a computer-readable storage medium for storing a computer program, wherein the computer program, when executed by a processor, implements the above-described eLoran receiver system delay calibration method based on multi-point ASF measurement provided in embodiments of the present invention.
[0061] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems, devices, and storage media disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.
[0062] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.
[0063] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.
[0064] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0065] The foregoing has provided a detailed description of the delay calibration method, system, device, and storage medium for an eLoran receiver system based on multi-point ASF measurement provided by this invention. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.
Claims
1. A method of eLoran receiver system delay calibration based on multi- point ASF measurements, characterized by, The method comprises the following steps: S1, establishing a reference point in a calibration area, continuously monitoring the reference point by using a pre-built ASF monitoring system, and obtaining an ASF time component of the reference point; S2, selecting multiple measurement points in the calibration area, obtaining an ASF measured value of each measurement point by using a reference receiver, performing space-time separation on the ASF measured value of each measurement point based on the ASF time component of the reference point, and obtaining an ASF space component of each measurement point; S3, constructing a joint inversion model taking system delay and segmented ground conductivity of a propagation path as targets based on the ASF space component of each measurement point and an ASF theoretical value of each measurement point, and solving the joint inversion model by using an optimization algorithm to obtain the system delay of the reference receiver; S4, selecting a fixed calibration point, monitoring the fixed calibration point by using the ASF monitoring system to obtain an ASF time component of the fixed calibration point, placing the reference receiver whose system delay has been calibrated at the fixed calibration point for short-time measurement, and determining an ASF space reference value of the fixed calibration point in combination with the ASF time component of the fixed calibration point in a corresponding time period; S5, placing a receiver to be calibrated at the fixed calibration point for short-time ASF measurement, obtaining a corresponding ASF time component from the fixed calibration point based on a measurement time period, and calculating the system delay of the receiver to be calibrated in combination with the ASF space reference value of the fixed calibration point.
2. The method of claim 1, wherein the method further comprises: In the S1, the ASF monitoring system is continuously monitored at the reference point to obtain the ASF time component of the reference point, which comprises the following steps: A plurality of days of monitoring data with stable weather conditions are selected, an ASF measured value of a fixed time period of each day is extracted and an average value is calculated, average values of the plurality of days are averaged to obtain an ASF space reference value of the reference point; The ASF measured value of the reference point is subtracted from the corresponding ASF space reference value to obtain the ASF time component of the reference point.
3. The method of claim 1, wherein the method further comprises: In the S2, the ASF time component of the reference point is used to perform space-time separation on the ASF measured value of each measurement point to obtain the ASF space component of each measurement point, which comprises the following steps: The reference point ASF time component corresponding to the measurement point observation time period is extracted, and an average value is taken as the ASF time component of the measurement point; The ASF measured value of the measurement point is subtracted from the corresponding ASF time component to obtain the ASF space component of the measurement point.
4. The method of claim 1, wherein the method further comprises: The objective function of the joint inversion model in the S3 is as follows: wherein: is the ASF spatial component (including system delay) for the th measurement point; is the ASF theoretical value for the th measurement point; denotes a parameter of the propagation path model for the th measurement point, wherein denotes a distribution of the path geoconductivity, denotes the distance of the th measurement point for the respective segment; denotes the measurement point.
5. A method of eLoran receiver system delay calibration based on multi- point ASF measurements according to claim 4, characterized in that, The objective function of the joint inversion model in the S3 is solved by using an optimization algorithm to obtain the system delay of the reference receiver, which comprises the following steps: S31, combining a ground conductivity map and topographic data of an experimental area to divide the propagation path into N segments, setting a value range of the conductivity of each segment, and preliminarily estimating a value interval of the system delay according to the distribution of the ASF theoretical value of the experimental area; S32, randomly initializing a preset number of search agent positions within the parameter constraint range, and the expression is as follows: wherein: is a random number in the range [0, 1]; is the lower limit of the j-th dimensional parameter, ; is the upper limit of the j-th dimensional parameter, ; S33, calculating the fitness of all search agents according to the joint inversion objective function, and the position of the search agent with the minimum fitness is the current optimal solution. S34, calculate the energy coefficient, if the energy coefficient > 1, the search agent updates the position by long-distance migration or tunneling behavior; if the energy coefficient <= 1, the search agent updates the position by foraging or avoiding natural enemy behavior, and re-determines the current optimal solution; S35, repeat S34 until the maximum number of iterations is reached, and output the current optimal position, that is, the system delay of the reference receiver is obtained.
6. The method of claim 1, wherein, The specific process of S4 is: By measuring at the fixed calibration point by the reference receiver, the measured value of the ASF of the fixed calibration point is obtained; The time component of the ASF from the reference point during the measurement period is obtained; The measured value of the ASF of the fixed calibration point is subtracted from the time component of the ASF of the reference point to obtain the spatial reference value of the ASF of the fixed calibration point.
7. The method of claim 1, wherein the method further comprises: The expression for calculating the system delay of the receiver to be calibrated in S5 is as follows: wherein: is the ASF measurement of the receiver to be calibrated including the system delay; is the ASF time component of the fixed calibration point corresponding to the measurement period; is the spatial reference value of the fixed calibration point; is the system delay.
8. A system for calibrating the system delay of an eLoran receiver based on multi- point ASF measurements, for implementing the method of any one of claims 1 to 7, characterized in that, It comprises: A first acquisition module for establishing a reference point in a calibration area, continuously monitoring the reference point using a pre-built ASF monitoring system, and acquiring the time component of the ASF of the reference point; A second acquisition module for selecting multiple measurement points in the calibration area, acquiring the measured value of the ASF of each measurement point using a reference receiver, and performing space-time separation on the measured value of the ASF of each measurement point based on the time component of the ASF of the reference point to obtain the spatial component of the ASF of each measurement point; A solving module for constructing a joint inversion model with the system delay and the segmented geoelectric conductivity of the propagation path as the target based on the spatial component of the ASF of each measurement point and the theoretical value of the ASF of each measurement point, and solving by an optimization algorithm to obtain the system delay of the reference receiver; A measurement module for selecting a fixed calibration point, acquiring the time component of the ASF of the fixed calibration point, placing the reference receiver calibrated for the system delay at the fixed calibration point for short-time measurement, and combining the time component of the ASF of the fixed calibration point during the corresponding period to determine the spatial reference value of the ASF of the fixed calibration point; An output module for placing the receiver to be calibrated at the fixed calibration point for short-time ASF measurement, acquiring the corresponding time component of the ASF from the fixed calibration point during the measurement period, and combining the spatial reference value of the ASF of the fixed calibration point to calculate the system delay of the receiver to be calibrated.
9. A delay calibration device for an eLoran receiver system based on multi-point ASF measurement, characterized in that, It comprises a processor and a memory, wherein the processor implements the eLoran receiver system delay calibration method based on multi-point ASF measurement as claimed in any one of claims 1 to 7 when executing the computer program saved in the memory.
10. A computer-readable storage medium, characterized in that, It is used for storing a computer program, wherein the computer program is executed by a processor to implement the eLoran receiver system delay calibration method based on multi-point ASF measurement as claimed in any one of claims 1 to 7.