Satellite combination selection method based on optimal DOP value

Abstract

The invention provides a satellite combination selection method based on an optimal DOP value, and the method comprises the steps: obtaining all visible satellites through obtaining satellite constellation ephemeris data and service region position information; calculating the visible time of the satellite to the service area according to the movement speed of the satellite and the pitch angle; and selecting the satellite combination with the optimal DOP value from the satellites meeting the visible time requirement. The method is clear in physical significance, small in calculation amount, adaptive to the satellite-borne software operation environment, effective in screening result and high in service stability, and the positioning precision and the practical value of the satellite navigation enhancement system can be remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of communication and navigation satellite technology, and in particular to a satellite combination selection method based on the optimal DOP value. Background Technology

[0002] In satellite navigation systems, the navigation augmentation point beam signals broadcast by satellites are the core carriers for achieving high-precision positioning and timing services. During the positioning and timing process, the spatial distribution geometry of the satellite array is a key factor affecting the accuracy of navigation and positioning services, and the quality of this geometry can be quantitatively characterized by the Dilution of Precision (DOP) value.

[0003] Specifically, the DOP value is directly related to the spatial distribution of the satellite constellation: a smaller DOP value indicates a more dispersed spatial distribution and a more robust geometric configuration of the satellite constellation, resulting in less impact of ranging errors on the final positioning result and higher navigation and positioning service accuracy. Conversely, a larger DOP value indicates a more concentrated spatial distribution and a poorer geometric configuration of the satellite constellation, which may lead to a larger positioning result even with high ranging accuracy. Therefore, selecting a satellite constellation that achieves the optimal DOP value is a core technical means to improve navigation and positioning accuracy during satellite constellation planning and navigation enhancement services.

[0004] In existing technologies, the mainstream method for obtaining the optimal DOP value satellite combination is the enumeration method. Its core logic is: based on the observation model of satellite navigation and positioning, a design matrix G is constructed, and G is obtained through multiple matrix operations. T The G matrix is ​​inverted, and the DOP values ​​corresponding to different satellite combinations are calculated. Finally, the target combination with the optimal DOP value is selected.

[0005] However, the above enumeration method has significant drawbacks in practical applications and is difficult to adapt to the operational requirements of satellite onboard software. The specific problems are as follows: The enumeration method requires traversing and calculating a large number of satellite combinations, and for each combination, the design matrix G needs to be constructed and G... T The multi-step matrix operations, including G matrix operations, inverse matrix solving, and DOP value calculation, involve high overall computational complexity and place stringent demands on hardware computing power and storage resources. However, satellite-borne software is limited by the size and power consumption of onboard equipment, resulting in limited computing power and storage resources, making it difficult to handle the aforementioned large-scale computational tasks. Consequently, the enumeration method cannot be effectively implemented in the satellite-borne software.

[0006] The enumeration method selects satellite combinations based solely on theoretical calculations, without considering the actual visibility status of the satellites. As a result, the satellite combinations with the optimal DOP value often include invisible satellites that are obstructed or outside the signal coverage area. Such combinations cannot be applied to actual navigation and positioning services, thus reducing the practical value of the method.

[0007] Existing methods do not take into account the orbital patterns and operational status of satellites. The selected satellite combinations may only meet the optimal DOP value requirements for a short period of time, making it impossible to maintain stable navigation enhancement signal broadcasting and ensuring continuous positioning and timing service time.

[0008] In summary, in response to the mission requirements of satellite constellation planning and broadcasting point beam navigation enhancement signals, there is an urgent need to propose a satellite combination selection method that has low computational cost, high combination effectiveness, and can guarantee service time, so as to solve the above-mentioned problems of existing technologies, achieve efficient screening of satellite combinations with optimal DOP values, and improve the accuracy of navigation and positioning services. Summary of the Invention

[0009] This invention finds a combination of satellites with a wide spatial distribution by requiring less computation, thereby obtaining the optimal geometric configuration and reducing the impact on positioning results.

[0010] This invention provides a satellite combination selection method based on optimal DOP value, comprising: Obtain satellite constellation ephemeris data and service area location information; Calculate the elevation angle from the user to the satellites based on satellite constellation ephemeris data and service area location information, and obtain all visible satellites; Calculate the visibility time of all visible satellites in the service area based on the satellite's velocity and the elevation angle. Select a satellite combination from among those that meet the visibility time requirement; and Verification of DOP value for satellite constellation.

[0011] In one embodiment of the present invention, the service area location information includes the orbital parameters, time, attitude information of each satellite, and the latitude, longitude, and altitude information of the ground station.

[0012] In one embodiment of the present invention, all visible satellites are obtained by using an elevation angle of 10 degrees as the masking angle.

[0013] In one embodiment of the present invention, selecting the satellite combination with the optimal DOP value from among the satellites that meet the visibility time requirement includes: Satellites with a visibility time of more than one hour were selected as candidate satellites. Among the satellites that meet the service time requirements, M satellites are selected to obtain the optimal combination of satellites in spatial distribution.

[0014] In one embodiment of the present invention, there are N candidate satellites, where N∈[7,11].

[0015] In one embodiment of the present invention, when M is 4, the spatial distribution geometry of the satellite is optimal.

[0016] In one embodiment of the present invention, selecting M satellites from those meeting the service time requirements to obtain the optimal spatially distributed satellite combination includes: Choose the satellite with the highest elevation angle from among N candidate satellites as the first satellite; The second satellite was selected as the antipodal satellite, whose azimuth differed from that of the first satellite by approximately 180 degrees. Choose the satellite with the largest area that forms a spatial triangle with the first two satellites as the third satellite; The satellite with the largest tetrahedral volume in space, selected from the first three satellites, will be the fourth satellite.

[0017] In one embodiment of the present invention, the verification of the DOP value of the satellite combination includes calculating the square of the volume of the tetrahedron spanned by the satellite direction vectors. The larger the value, the smaller the DOP value of the satellite combination and the better the geometric configuration.

[0018] The present invention has the following beneficial effects: (1) The satellite combination screening logic is optimized, which can screen satellite combinations with a wide spatial distribution with a small amount of computation, without performing complex operations such as frequent matrix operations and inversion. This feature effectively reduces the demand for computing power and storage resources of on-board equipment, perfectly adapts to the running limitations of on-board software, and significantly improves the execution efficiency and deployment feasibility of the method in the on-board environment.

[0019] (2) In the process of selecting the optimal DOP value satellite combination, the actual visibility status of the satellites is fully considered, and invisible satellites that are blocked or outside the signal coverage range can be directly excluded, thus avoiding the generation of invalid satellite combinations from the source. Compared with the traditional enumeration method, which outputs invalid solutions containing invisible satellites, the satellite combination output by this method can be directly applied to actual navigation and positioning services.

[0020] (3) The relationship between the spatial distribution geometry of satellites and DOP values ​​is discussed. The physical meaning is clear and easy to understand, without relying on complex mathematical derivations or black box models. Attached Figure Description

[0021] Figure 1 A flowchart of a satellite combination selection method based on the optimal DOP value in one embodiment of the present invention is shown; Figure 2 A simulation diagram of satellite visibility in a user service area is shown in one embodiment of the present invention; Figure 3 A spatial distribution diagram of satellite arrays according to an embodiment of the present invention is shown; and Figure 4 A comparison chart of optimal DOP values ​​in one embodiment of the present invention is shown. Detailed Implementation

[0022] In the following description, the invention is described with reference to various embodiments. However, those skilled in the art will recognize that the embodiments may be practiced without one or more specific details or with other alternatives and / or additional methods, materials, or components. In other instances, well-known structures, materials, or operations are not shown or described in detail so as not to obscure the inventive points of the invention. Similarly, for illustrative purposes, specific quantities, materials, and configurations are set forth to provide a comprehensive understanding of embodiments of the invention. However, the invention is not limited to these specific details.

[0023] In this invention, the various embodiments are merely intended to illustrate the solutions of the invention and should not be construed as limiting.

[0024] In this specification, references to "an embodiment" or "this embodiment" mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. The phrase "in one embodiment" appearing throughout this specification does not necessarily refer to the same embodiment in all instances.

[0025] Furthermore, the numbering of the steps in the methods of the present invention does not limit the execution order of the method steps. Unless otherwise specified, the method steps may be executed in different orders.

[0026] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0027] Figure 1 A flowchart of a satellite combination selection method based on the optimal DOP value is shown in one embodiment of the present invention.

[0028] like Figure 1 As shown, in one embodiment of the present invention, the satellite combination selection method based on the optimal DOP value includes: S100, Data Acquisition: Acquire satellite constellation ephemeris data and service area location information, specifically including: orbital parameters, time, attitude information of each satellite, and latitude, longitude, and altitude information of the ground station.

[0029] S200, Service Time Calculation: Based on satellite orbital parameters, attitude information, and service area latitude and longitude information, calculate the elevation angle from the user to the satellite, and use 10 degrees as the elevation angle mask to obtain all visible satellites.

[0030] S300, Statistical Satellite Visibility Calculation, calculates the satellite's visibility time in the service area based on the satellite's motion speed and the user's elevation angle in the direction of the satellite.

[0031] S400. Select a satellite combination. Among the satellites that meet the service time requirements, select a satellite combination based on high elevation angle and wide spatial distribution. The satellite combination has M satellites. When M≥4, the number of satellites required for positioning service is met. In this embodiment, the following steps are included: Satellites with a visibility time of more than one hour are selected as candidate satellites. There are a total of N candidate satellites, and N∈[7,11] based on the satellite simulation visibility. Among the satellites that meet the service time requirements, M satellites are selected to obtain the optimal combination of satellites in spatial distribution. M is set to 4, that is, 4 satellites are selected from N satellites, and the spatial distribution geometry of the 4 satellites is optimal. The DOP value of the satellite constellation is calculated by taking the square of the volume of the tetrahedron spanned by the satellite direction vectors. The larger the value, the smaller the DOP value of the satellite constellation and the better the geometric configuration.

[0032] The optimal satellite combination selected from four satellites includes: Choose the satellite with the highest elevation angle from among N candidate satellites as the first satellite; The second satellite was selected as the antipodal satellite, whose azimuth differed from that of the first satellite by approximately 180 degrees. Choose the satellite with the largest area that forms a spatial triangle with the first two satellites as the third satellite; The satellite with the largest tetrahedral volume in space, selected from the first three satellites, will be the fourth satellite.

[0033] This method is a satellite combination selection method based on the optimal DOP value. Analyzing from the definition of the DOP value, its calculation matrix (G...) T The determinant of G) corresponds to the square of the volume of the space spanned by the satellite direction vectors. The more open the spatial distribution of the satellite combination, the smaller the corresponding DOP value, the better the spatial geometry, and the higher the navigation and positioning accuracy. The physical meaning of this method is clear and explicit.

[0034] In the satellite combination screening stage, the method first combines satellite orbital parameters and attitude information to accurately calculate the visibility of satellites to the user area, directly eliminating invalid solutions such as invisible satellites; secondly, based on satellite elevation angle data, it calculates the effective visibility duration of satellites to the user area, selects satellites with a service duration of more than one hour, and removes satellites that are about to leave the visibility range, which has outstanding practical engineering application value.

[0035] This method offers significant computational advantages, requiring only one matrix operation throughout the entire process. Taking the scenario of selecting the optimal 4 satellites from 11 satellites as an example, the exhaustive method would require 330 DOP matrix operations (G... T The computational complexity of the G) operation far exceeds that of this method; at the same time, the DOP value corresponding to the satellite combination selected by this method has a very high degree of agreement with the theoretical optimal solution, and the ratio between the two is only 1.037, which can achieve near-optimal positioning effect.

[0036] Figure 2A schematic diagram of the satellite visibility simulation results for a user service area is shown in one embodiment of the present invention.

[0037] In one specific embodiment of the present invention, 24 navigation satellites deployed in medium Earth orbit (MEO) are used as the basic data source, and the goal is to screen out the combination of 4 satellites with the optimal DOP value to carry out the verification and analysis of the satellite selection method.

[0038] like Figure 2 As shown, in the initial stage of the method, satellite visibility simulation analysis is first performed on the target user's service area to define the effective range for subsequent satellite combination selection. The simulation results show that within the user's service area, the number of visible satellites fluctuates between 7 and 11 at different times, with an average of 9.58 visible satellites throughout the entire period. This result provides sufficient candidate samples for the subsequent selection of the optimal satellite combination.

[0039] Figure 3 A schematic diagram of the spatial distribution of the optimal satellite combination obtained by screening in one embodiment of the present invention is shown.

[0040] Based on the completed satellite visibility analysis of the user service area, the satellite selection method described in this invention, according to satellite orbital parameters, attitude information, and spatial distribution configuration evaluation criteria, accurately selects four satellites with the most open spatial distribution from the candidate visible satellites. Their three-dimensional spatial distribution is as follows: Figure 3 As shown in the figure, the four selected satellites are evenly distributed in the celestial coordinate system, possessing a good spatial geometric configuration, which lays the core conditions for achieving low DOP value and high-precision positioning.

[0041] Figure 4 The diagram shows the comparison and verification results of the optimal DOP value in one embodiment of the present invention.

[0042] To verify the effectiveness and accuracy of this method, the DOP values ​​of the satellite combinations selected by this method are compared and analyzed with the theoretically optimal DOP values ​​obtained by exhaustively searching through all possible satellite combinations. The comparison results are as follows: Figure 4 As shown in the figure, the data indicates that the DOP values ​​corresponding to the satellite combinations selected by this method are in extremely high agreement with the theoretically optimal DOP values ​​obtained by the exhaustive method, with a ratio of only 1.037. This result fully demonstrates that this method can achieve a selection effect that is almost identical to the theoretically optimal solution while significantly reducing the computational load.

[0043] Although various embodiments of the invention have been described above, it should be understood that they are presented by way of example only and not as limitations. It will be apparent to those skilled in the art that various combinations, modifications, and alterations can be made without departing from the spirit and scope of the invention. Therefore, the breadth and scope of the invention disclosed herein should not be limited by the exemplary embodiments disclosed above, but should be defined solely by the appended claims and their equivalents.

Claims

1. A satellite combination selection method based on optimal DOP value, characterized in that, include: Obtain satellite constellation ephemeris data and service area location information; Calculate the elevation angle from the user to the satellites based on satellite constellation ephemeris data and service area location information, and obtain all visible satellites; Calculate the visibility time of all visible satellites in the service area based on the satellite's velocity and the elevation angle. Select a satellite combination from among the satellites that meet the visibility time requirement; as well as Verification was performed by calculating the DOP value of the satellite constellation.

2. The method according to claim 1, characterized in that, The service area location information includes the orbital parameters, time, attitude information of each satellite, and the latitude, longitude, and altitude information of the ground station.

3. The method according to claim 1, characterized in that, This includes acquiring all visible satellites using an elevation angle and eclipse angle of 10 degrees.

4. The method according to claim 1, characterized in that, The selection of satellite combinations from among those meeting the visibility time requirement includes: Satellites with a visibility time of more than one hour were selected as candidate satellites. Among the satellites that meet the service time requirements, M satellites are selected to obtain the optimal combination of satellites in spatial distribution.

5. The method according to claim 4, characterized in that, There are N candidate satellites in total, where N∈[7,11].

6. The method according to claim 4, characterized in that, When M is 4, the spatial distribution geometry of the satellite is optimal.

7. The method according to claim 4, characterized in that, Among the satellites that meet the service time requirements, M satellites are selected to obtain the optimal spatial distribution of satellite combinations, including: Choose the satellite with the highest elevation angle from among N candidate satellites as the first satellite; The second satellite was selected as the antipodal satellite, whose azimuth differed from that of the first satellite by approximately 180 degrees. Choose the satellite with the largest area that forms a spatial triangle with the first two satellites as the third satellite; The satellite with the largest tetrahedral volume in space, selected from the first three satellites, will be the fourth satellite.

8. The method according to claim 1, characterized in that, Verification by calculating the DOP value of the satellite constellation includes calculating the square of the volume of the tetrahedron spanned by the satellite direction vectors. The larger the value, the smaller the DOP value of the satellite constellation and the better the geometric configuration.

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