A method for selecting GNSS satellites based on reflection measurement detection area

Abstract

A method for selecting GNSS satellites based on a reflection measurement detection area, the selection method comprising: determining a target GNSS-R satellite visible to a target observation area; taking the direction from each boundary point to the target GNSS-R satellite as the direction of a reflected signal at the boundary point, and obtaining the direction of an incident signal at the boundary point according to the direction of the reflected signal at the boundary point and a normal vector of the boundary point, wherein the normal vector of the boundary point is a normal vector of the boundary point on the surface of an earth ellipsoid; determining the position range of GNSS satellites in a global positioning navigation system according to the direction of the incident signal at all boundary points, the theoretical height of GNSS satellites in a global positioning navigation system relative to the center of an earth ellipsoid, and the vectors from all boundary points to the center of an earth ellipsoid; selecting a GNSS satellite whose actual position is within the position range of the global positioning navigation system in the global positioning navigation system, and the signal sent by the selected GNSS satellite in the global positioning navigation system is used to realize detection of the target observation area.

Description

Technical Field

[0001] The present invention relates to the field of satellite detection, and in particular to a method for selecting a GNSS satellite based on a reflection measurement detection area. Background Art

[0002] As a passive remote sensing technology, Global Navigation Satellite System Reflectometry (GNSS-R) has the advantages of low cost and high temporal and spatial resolution. After analyzing the GNSS satellite signals of the Global Navigation Satellite System (GNSS) reflected by the earth's surface, the sea surface height, sea surface wind field, sea ice distribution, soil moisture and biomass can be detected. The spaceborne GNSS-R system is to carry the GNSS-R receiver and signal receiving antenna on the GNSS-R satellite, and achieve wide coverage and high-density observation by simultaneously receiving the surface reflection signals of different GNSS satellites. Generally, GNSS-R satellites are low-orbit satellites. Due to the size and weight restrictions of low-orbit satellites, they are often unable to carry large computing equipment and large-capacity data storage, which limits the number of channels for the spaceborne GNSS-R receiver to receive and process the reflected signals. Affected by factors such as processing power, hardware resources and instrument power consumption, GNSS-R receivers usually fix the number of channels for signal reception. Therefore, GNSS-R receivers cannot process the reflected signals from all visible GNSS satellites. GNSS-R receivers usually selectively receive signals with higher power and better quality within the coverage of the antenna. However, these higher power and better quality signals may not come from the same observation area, so the reflected signals automatically selected and received by the GNSS-R receiver cannot detect the target observation area. Summary of the invention

[0003] In view of this, the present invention provides a method for selecting a GNSS satellite based on a reflection measurement detection area, the selection method is applied to a global positioning navigation system orbiting the earth ellipsoid, the global positioning navigation system includes multiple GNSS satellites, and the selection method includes:

[0004] Determining a target GNSS-R satellite visible to a target observation area; wherein the target GNSS-R satellite is used to detect a signal emitted by at least one GNSS satellite and reflected by the target observation area; the target observation area is located on the earth ellipsoid, and the target observation area is determined by a plurality of boundary points located on the earth ellipsoid;

[0005] The direction from each boundary point to the target GNSS-R satellite is taken as the direction of the reflected signal at the boundary point, and the direction of the incident signal at the boundary point is obtained according to the direction of the reflected signal at the boundary point and the normal vector of the boundary point, wherein the normal vector of the boundary point is the normal vector of the boundary point on the surface of the earth ellipsoid;

[0006] Determine the position range of the GNSS satellite in the global positioning navigation system according to the direction of the incident signal at all boundary points, the theoretical height of the GNSS satellite in the global positioning navigation system relative to the center of the earth ellipsoid, and the vectors from all boundary points to the center of the earth ellipsoid;

[0007] In the global positioning navigation system, a GNSS satellite whose actual position is within the position range is selected, and the signal sent by the selected GNSS satellite in the global positioning navigation system is used to realize the detection of the target observation area.

[0008] According to an embodiment of the present invention, obtaining the direction of the incident signal at the boundary point according to the direction of the reflected signal at the boundary point and the normal vector of the boundary point includes:

[0009] Determine a first angle θ according to the direction of the reflection signal at the boundary point and the normal vector at the boundary point, where the first angle θ is the angle between the reflection signal at the boundary point and the normal vector at the boundary point;

[0010] The direction of the incident signal at the boundary point is determined according to the direction of the reflected signal at the boundary point, the normal vector of the boundary point and the first angle θ.

[0011] According to an embodiment of the present invention, determining the position range of the GNSS satellite in the global positioning navigation system according to the direction of the incident signal at all boundary points, the theoretical height of the GNSS satellite in the global positioning navigation system relative to the center of the earth ellipsoid, and the vector from all boundary points to the center of the earth ellipsoid includes:

[0012] For each boundary point, the theoretical position of the GNSS satellite in the global positioning navigation system corresponding to each boundary point is obtained according to the direction of the incident signal at the boundary point, the theoretical height of the GNSS satellite in the global positioning navigation system relative to the center of the earth ellipsoid, and the vector from the boundary point to the center of the earth ellipsoid;

[0013] The position range of the GNSS satellite in the global positioning navigation system is obtained according to all theoretical positions of the GNSS satellite in the global positioning navigation system corresponding to all boundary points.

[0014] According to an embodiment of the present invention, the direction of the incident signal at the boundary point is the direction from the theoretical position of the GNSS satellite in the global positioning navigation system to the boundary point;

[0015] The theoretical position of the GNSS satellite in the global positioning navigation system corresponding to the boundary point is obtained according to the direction of the incident signal at the boundary point, the theoretical height of the GNSS satellite in the global positioning navigation system relative to the center of the earth ellipsoid, and the vector from the boundary point to the center of the earth ellipsoid, including:

[0016] In a triangle established with the theoretical position of the GNSS satellite in the global positioning navigation system, the boundary point and the center of the earth ellipsoid, the triangle is solved according to the direction from the theoretical position of the GNSS satellite in the global positioning navigation system to the boundary point, the vector from the boundary point to the center of the earth ellipsoid and the theoretical height of the GNSS satellite in the global positioning navigation system relative to the center of the earth ellipsoid, and the theoretical position of the GNSS satellite in the global positioning navigation system corresponding to the boundary point is obtained.

[0017] According to an embodiment of the present invention, after obtaining the position range of the GNSS satellite in the global positioning navigation system, the selection method further includes:

[0018] The position range is converted into a theoretical altitude angle range and a theoretical azimuth angle range based on the target GNSS-R satellite.

[0019] According to an embodiment of the present invention, the selection method further includes:

[0020] In the global positioning navigation system, a GNSS satellite is selected whose actual elevation angle relative to the target GNSS-R satellite is within the elevation angle range and whose actual azimuth angle relative to the target GNSS-R satellite is within the azimuth angle range.

[0021] According to an embodiment of the present invention, the theoretical height of a GNSS satellite in a global positioning navigation system relative to the center of the earth ellipsoid is equal to the sum of the theoretical orbital height of the GNSS satellite in the global positioning navigation system and the radius of the earth.

[0022] According to an embodiment of the present invention, determining a target GNSS-R satellite visible to a target observation area includes:

[0023] Determine the direction from the center of the target observation area to at least one GNSS-R satellite, that is, calculate the altitude angle of at least one GNSS-R satellite. The direction from the center of the target observation area to each GNSS-R satellite is the direction of the GNSS-R satellite;

[0024] Determine at least one second angle according to the direction of at least one GNSS-R satellite and the normal vector of the center point of the target observation area, the second angle being the angle between the direction of the GNSS-R satellite and the normal vector of the center point of the target observation area, the normal vector of the center point of the target observation area being the normal vector of the center point of the target observation area on the surface of the earth ellipsoid;

[0025] A GNSS-R satellite satisfying a second angle less than 90 degrees is selected from at least one GNSS-R satellite as a target GNSS-R satellite.

[0026] According to an embodiment of the present invention, a method for determining a target observation area includes:

[0027] Identify all boundary points;

[0028] The target observation area is determined based on the coordinates of all boundary points.

[0029] According to an embodiment of the present invention, after selecting a GNSS satellite whose actual position is within a specified position range of the global positioning navigation system in the global positioning navigation system, the selection method further includes:

[0030] The target GNSS-R satellite receives and processes the signal from the selected GNSS satellite in the global positioning navigation system to achieve detection of the target observation area.

[0031] According to an embodiment of the present invention, the target observation area is determined by boundary points, and the position range of the GNSS satellite in the global positioning navigation system is determined by utilizing the direction of the incident signal at all boundary points, the theoretical height of the GNSS satellite in the global positioning navigation system relative to the center of the earth ellipsoid, and the vectors from all boundary points to the center of the earth ellipsoid. Satellites in the global positioning navigation system whose actual positions are within the position range of the GNSS satellite are selected, and the selected GNSS satellites can be used for targeted detection of the target observation area. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0033] Figure 1 A flow chart of a method for selecting a GNSS satellite based on a reflection measurement detection area provided in accordance with an embodiment of the present invention is shown;

[0034] Figure 2 A schematic diagram showing a method for selecting a GNSS satellite based on a reflection measurement detection area provided in accordance with an embodiment of the present invention is shown;

[0035] Figure 3 A flow chart of a method for selecting a GNSS satellite based on a reflection measurement detection area according to another embodiment of the present invention is shown;

[0036] Figure 4A A schematic diagram of the selection result of a GNSS-R satellite according to a specific embodiment of the present invention is shown;

[0037] Figure 4BShows Figure 4A A partial enlarged view of part A;

[0038] Figure 4C Shows Figure 4A A partial enlarged view of part B. DETAILED DESCRIPTION

[0039] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0040] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0041] All terms used herein, including technical and scientific terms, have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification, and should not be interpreted in an idealized or overly rigid manner.

[0042] When using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted as the meaning of the expression generally understood by those skilled in the art. For example, "a system having at least one of A, B, and C" should include but not be limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc. When using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted as the meaning of the expression generally understood by those skilled in the art. For example, "a system having at least one of A, B, or C" should include but not be limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.

[0043] It should also be noted that the directional terms mentioned in the embodiments, such as "upper", "lower", "front", "back", "left", "right", etc., are only for reference to the drawings and are not intended to limit the scope of protection of the present invention. Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or configurations will be omitted when they may cause confusion in the understanding of the present invention.

[0044] The collection, updating, analysis, processing, use, transmission, provision, disclosure, storage and other aspects of the data involved in the present invention (for example, including but not limited to user personal information) are in compliance with the provisions of relevant laws and regulations, are used for legitimate purposes, and do not violate public order and good morals. In particular, necessary measures are taken for user personal information to prevent illegal access to user personal information data and maintain the security of user personal information and network security.

[0045] Figure 1 A flow chart of a method for selecting a GNSS satellite based on a reflection measurement detection area provided according to an embodiment of the present invention is shown.

[0046] Figure 2 A schematic diagram of a method for selecting a GNSS satellite based on a reflection measurement detection area provided in accordance with an embodiment of the present invention is shown.

[0047] The above selection method is applied to the global positioning navigation system (GNSS system) orbiting the earth ellipsoid. Figure 2 The directions of the corresponding coordinate axes are also given in the figure. The global positioning navigation system includes multiple GNSS satellites, combined with Figure 1-Figure 2 The selection method includes operation S10 to operation S40.

[0048] In operation S10, a target GNSS-R satellite visible to the target observation area is determined, and the position of the target GNSS-R satellite is represented by R. The target GNSS-R satellite is used to detect the signal emitted by at least one GNSS satellite and reflected by the target observation area, and the position of the GNSS satellite is represented by T1; the target observation area is located on the earth ellipsoid, and the target observation area is determined by multiple boundary points located on the earth ellipsoid. For example, the boundary points may include four, namely S1, S2, S3 and S4, S1, S2, S3 and S4 constitute S area, i.e., the target observation area, and n2 is the normal vector of the center point of S area.

[0049] In operation S20, the direction from each boundary point to the target GNSS-R satellite is used as the direction of the reflected signal at the boundary point, and the direction of the incident signal at the boundary point is obtained according to the direction of the reflected signal at the boundary point and the normal vector of the boundary point, where the normal vector of the boundary point is the normal vector of the boundary point on the surface of the earth ellipsoid. The incident signal at the boundary point is a signal emitted from a GNSS satellite and incident on the boundary point. Figure 2 As shown, for example, the normal vector of the boundary point S1 on the surface of the earth ellipsoid is n1.

[0050] In operation S30, the position range of the GNSS satellite in the global positioning navigation system is determined according to the direction of the incident signal at all boundary points, the theoretical height of the GNSS satellite in the global positioning navigation system relative to the center of the earth ellipsoid, and the vectors from all boundary points to the center of the earth ellipsoid, and the position of the center of the earth ellipsoid is represented by O.

[0051] In operation S40, a GNSS satellite whose actual position is within the position range of the global positioning navigation system is selected in the global positioning navigation system, and a signal sent by the selected GNSS satellite in the global positioning navigation system is used to detect the target observation area.

[0052] According to an embodiment of the present invention, the selection method of the embodiment of the present invention can be used in different global positioning navigation systems. The GNSS-R constellation can be composed of 8 micro low-orbit satellites, which are equipped with GNSS-R detection payloads for monitoring and studying the structure and changes of tropical cyclones. The published data records detailed time, low-orbit satellite position and other information. In addition, according to the broadcast ephemeris of the published GNSS satellite, the position of the GNSS satellite at different times can be obtained.

[0053] According to an embodiment of the present invention, the target observation area is determined by boundary points, and the position range of the GNSS satellite in each global positioning navigation system is determined by utilizing the direction of the incident signals at all boundary points, the theoretical height of the GNSS satellite in each global positioning navigation system relative to the center of the earth ellipsoid, and the vectors from all boundary points to the center of the earth ellipsoid. Satellites in the global positioning navigation system whose actual positions are within the position range of the GNSS satellites are selected, and the selected GNSS satellites can be used for targeted detection of the target observation area.

[0054] Figure 3 A flow chart of a method for selecting a GNSS satellite based on a reflection measurement detection area provided in accordance with another embodiment of the present invention is shown.

[0055] Combination Figure 1 and Figure 3 In operation S10, the method for determining the target observation area includes the following steps.

[0056] First, determine all boundary points, that is, determine the coordinates of all boundary points (the longitude and latitude of the boundary points).

[0057] Secondly, the target observation area is determined according to the coordinates of all boundary points. Specifically, all boundary points together form a closed area, namely the target observation area, and the size and shape of the target observation area are determined by the given boundary point positions.

[0058] According to an embodiment of the present invention, the method for determining the target GNSS-R satellite visible to the target observation area in operation S10 can be obtained by the following method. First, the angle between the vector from the center of the target detection area to each GNSS-R satellite and the normal vector of the boundary point of the target detection area can be calculated according to the position of each GNSS-R satellite relative to the target detection area, and whether the GNSS-R satellite meets the geometric conditions of the reflection measurement can be determined according to the size of the angle, thereby determining the target GNSS-R satellite.

[0059] Specifically, determining the target GNSS-R satellite visible to the target observation area in operation S10 includes operating the following steps.

[0060] First, the altitude angle of at least one GNSS-R satellite is calculated. Specifically, the direction from the center of the target observation area to at least one GNSS-R satellite is determined, and the direction from the center of the target observation area to each GNSS-R satellite is the direction of the GNSS-R satellite or the altitude angle of the GNSS-R satellite.

[0061] Secondly, at least one second angle is determined based on the direction of at least one GNSS-R satellite and the normal vector of the center point of the target observation area. The second angle is the angle between the direction of the GNSS-R satellite and the normal vector of the center point of the target observation area. The normal vector of the center point of the target observation area is the normal vector of the center point of the target observation area on the surface of the earth ellipsoid.

[0062] Again, it is determined whether each of the multiple GNSS-R satellites is visible. A GNSS-R satellite that satisfies the second angle of less than 90 degrees is selected from at least one GNSS-R satellite as a target GNSS-R satellite. The GNSS-R satellite that satisfies the second angle of less than 90 degrees satisfies the geometric condition of reflection measurement, that is, the GNSS-R satellite is visible relative to the target observation area.

[0063] According to an embodiment of the present invention, in operation S20, obtaining the direction of the incident signal at the boundary point according to the direction of the reflected signal at the boundary point and the normal vector at the boundary point includes the following steps.

[0064] First, the angle θ between the reflected signal at the boundary point and the normal vector at the boundary point is determined according to the direction of the reflected signal at the boundary point and the normal vector at the boundary point;

[0065] Secondly, the straight line where the reflection signal is located is rotated by 2θ along a preset direction to obtain a rotated straight line, where the preset direction is the direction of the normal vector of the self-reflection signal pointing to the boundary point;

[0066] Again, the direction of the incident signal at the boundary point is determined based on the rotated straight line.

[0067] According to an embodiment of the present invention, the position of the target GNSS-R satellite at the time of observation satisfies certain geometric observation conditions with the target detection area. The angle θ (also called the reflection angle) between the direction of the reflected signal at each boundary point and the normal vector at the boundary point is calculated. According to Snell's reflection law, the boundary point is used as the mirror point, and θ is rotated by 2θ in the rotation plane to obtain a rotated straight line. The incident signal at the boundary point is on the straight line after rotation, and the direction of the incident signal at the boundary point is the direction pointing to the mirror point.

[0068] According to an embodiment of the present invention, in operation S30, the position range of the GNSS satellites in the global positioning navigation system is determined according to the direction of the incident signal at all boundary points, the theoretical height of each GNSS satellite in the global positioning navigation system relative to the center of the earth ellipsoid, and the vectors from all boundary points to the center of the earth ellipsoid, including the following steps.

[0069] First, for each boundary point, the theoretical position of the GNSS satellite in the global positioning navigation system corresponding to each boundary point is obtained according to the direction of the incident signal at the boundary point, the theoretical height of the GNSS satellite in the global positioning navigation system relative to the center of the earth ellipsoid, and the vector from the boundary point to the center of the earth ellipsoid.

[0070] According to an embodiment of the present invention, the direction of the incident signal at the boundary point is the direction of the theoretical position of the GNSS satellite in the global positioning navigation system to the boundary point. The theoretical position of the GNSS satellite in the global positioning navigation system corresponding to the boundary point is obtained according to the direction of the incident signal at the boundary point, the theoretical height of each GNSS satellite in the global positioning navigation system relative to the center of the earth ellipsoid, and the vector from the boundary point to the center of the earth ellipsoid, including: in a triangle established with the theoretical position of the GNSS satellite in the global positioning navigation system, the boundary point and the center of the earth ellipsoid, the triangle is solved according to the direction of the theoretical position of the GNSS satellite in the global positioning navigation system to the boundary point, the vector from the boundary point to the center of the earth ellipsoid and the theoretical height of the GNSS satellite in the global positioning navigation system relative to the center of the earth ellipsoid, and the theoretical position of the GNSS satellite in the global positioning navigation system corresponding to the boundary point is obtained. Wherein, the theoretical height of the GNSS satellite in the global positioning navigation system relative to the center of the earth ellipsoid is equal to the sum of the theoretical orbital height of the GNSS satellite in the global positioning navigation system and the radius of the earth.

[0071] Secondly, the position range of the GNSS satellite in the global positioning navigation system is obtained according to all theoretical positions of the GNSS satellite in the global positioning navigation system corresponding to all the boundary points.

[0072] According to an embodiment of the present invention, in the triangle formed by the GNSS satellite, the boundary point and the center of the reference ellipsoid in the global positioning navigation system, the direction of the vector from the GNSS satellite to the boundary point (i.e., the direction of the incident signal), the direction and distance from the center of the reference ellipsoid to the boundary point, and the theoretical height of the orbit of the GNSS satellite relative to the center of the earth ellipsoid are known. Based on the known conditions, the above triangle can be solved, and the position of the GNSS satellite corresponding to the boundary point can be obtained. The position range of the GNSS satellite in the global positioning navigation system can be obtained based on all theoretical positions of the GNSS satellite in the global positioning navigation system corresponding to all boundary points. This calculation method is applied to different global positioning navigation systems and the position range of the GNSS satellite in different global positioning navigation systems can be deduced from it.

[0073] According to an embodiment of the present invention, after obtaining the position range of the GNSS satellite in the global positioning navigation system, the selection method further includes: converting the position range into a theoretical altitude angle range and a theoretical azimuth angle range based on the target GNSS-R satellite.

[0074] The position range of the GNSS satellites in the global positioning navigation system is obtained according to all theoretical positions of the GNSS satellites in the global positioning navigation system corresponding to all boundary points, including: obtaining the altitude angle range according to the theoretical altitude angles of the GNSS satellites in the global positioning navigation system corresponding to all boundary points; and obtaining the azimuth angle range according to the theoretical azimuth angles of the GNSS satellites in the global positioning navigation system corresponding to all boundary points.

[0075] According to an embodiment of the present invention, the selection method further includes: determining whether each GNSS satellite is visible. Specifically, determining whether each GNSS satellite is visible relative to the target GNSS-R satellite based on a theoretical altitude angle range and a theoretical azimuth angle range of the target GNSS-R satellite and the actual position of each GNSS satellite in the global positioning navigation system. The actual position of each GNSS satellite can obtain the altitude angle and azimuth angle of the GNSS satellite relative to the target GNSS-R satellite.

[0076] According to an embodiment of the present invention, the above-mentioned selection method also includes: selecting and retaining GNSS satellites in the global positioning navigation system whose actual altitude angles relative to the target GNSS-R satellites are within the altitude angle range and whose actual azimuth angles relative to the target GNSS-R satellites are within the azimuth angle range, while discarding unselected GNSS satellites.

[0077] According to an embodiment of the present invention, after selecting a GNSS satellite whose actual position is within a specified position range of the global positioning navigation system in the global positioning navigation system, the above-mentioned selection method also includes: enabling the target GNSS-R satellite to receive and process signals from the selected GNSS satellites in all global positioning navigation systems to realize detection of the target observation area.

[0078] Figure 4A A schematic diagram of the selection result of a GNSS-R satellite provided according to a specific embodiment of the present invention is shown.

[0079] like Figure 4A As shown, the selection result of the GNSS-R satellite is obtained by approximating the earth ellipsoid by the WGS84 ellipsoid in the geocentric coordinate system.

[0080] Figure 4B Shows Figure 4A A partial enlarged view of part A.

[0081] Figure 4C Shows Figure 4A A partial enlarged view of part B.

[0082] like Figure 4A~Figure 4B As shown in the figure, the target observation area is determined by four boundary points. In the Earth-centered Earth-fixed coordinate system, the coordinates of the four boundary points are calculated to be: (41°N, 167°E), (45°N, 167°E), (43°N, 165°E) and (43°N, 169°E). Figure 4B In the figure, the five-pointed star is the position of the target GNSS-R satellite, represented by R, and the circle in the S area is the position of the four boundary points. The target observation area is determined by a closed area formed by the coordinates of the four boundary points. The size and shape of the target observation area can be adjusted according to the actual situation. The result of this example is as follows Figure 4A~Figure 4B The center of the selected target observation area is 43°N, 167°E. In the figure, the five-pointed star is the position of the GNSS-R satellite.

[0083] like Figure 4A and Figure 4C As shown, the hexagonal stars are all theoretical positions of GNSS satellites corresponding to all boundary points, represented by L1, L2, L3 and L4 respectively, and the squares are selected GNSS satellites, represented by L.

[0084] According to an embodiment of the present invention, by selecting GNSS satellites in the global positioning navigation system, and setting the GNSS-R satellite to receive the reflected signal of the selected GNSS satellite reflected from the target observation area, combined with the advantages of low cost and high spatiotemporal resolution of the GNSS-R system, under existing conditions, the coverage capability of GNSS-R for the set detection area is further improved. By continuously monitoring the wave height and sea wind conditions in the detection area, the marine environment of the target observation area can be constructed, the sea level height anomaly and sea wind anomaly in the target observation area can be monitored, and early warning can be given to reduce the risk of disasters. In short, this method can be combined with the technical characteristics of the GNSS-R system to improve the coverage capability and observation density of the GNSS-R satellite or constellation for the target detection area, thereby obtaining more abundant regional observation data, which plays a relatively important role.

[0085] The embodiments of the present invention are described above. However, these embodiments are only for the purpose of illustration, and are not intended to limit the scope of the present invention. Although each embodiment is described above, it does not mean that the measures in each embodiment cannot be used in combination. The scope of the present invention is defined by the attached claims and their equivalents. Without departing from the scope of the present invention, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present invention.

Claims

1. A method for selecting a GNSS satellite based on a reflection measurement detection area, the method being applied to a global positioning navigation system orbiting the earth ellipsoid, the global positioning navigation system comprising a plurality of GNSS satellites, characterized in that: The selection method includes: Determining a target GNSS-R satellite visible to a target observation area; wherein the target GNSS-R satellite is used to detect a signal emitted by at least one GNSS satellite and reflected by the target observation area; the target observation area is located on the earth ellipsoid, and the target observation area is determined by a plurality of boundary points located on the earth ellipsoid; Taking the direction from each boundary point to the target GNSS-R satellite as the direction of the reflected signal at the boundary point, and obtaining the direction of the incident signal at the boundary point according to the direction of the reflected signal at the boundary point and the normal vector of the boundary point, wherein the normal vector of the boundary point is the normal vector of the boundary point on the surface of the earth ellipsoid; Determine the position range of the GNSS satellite in the global positioning navigation system according to the direction of the incident signal at all boundary points, the theoretical height of the GNSS satellite in the global positioning navigation system relative to the center of the earth ellipsoid, and the vectors from all boundary points to the center of the earth ellipsoid; A GNSS satellite whose actual position is within the position range is selected in the global positioning navigation system, and a signal sent by the selected GNSS satellite in the global positioning navigation system is used to detect the target observation area.

2. The selection method according to claim 1, characterized in that: Obtaining the direction of the incident signal at the boundary point according to the direction of the reflected signal at the boundary point and the normal vector of the boundary point includes: Determine a first angle θ according to the direction of the reflection signal at the boundary point and the normal vector of the boundary point, wherein the first angle θ is the angle between the reflection signal at the boundary point and the normal vector of the boundary point; The direction of the incident signal at the boundary point is determined according to the direction of the reflected signal at the boundary point, the normal vector of the boundary point and the first angle θ.

3. The selection method according to claim 1, characterized in that: Determining the position range of the GNSS satellite in the global positioning navigation system according to the direction of the incident signal at all boundary points, the theoretical height of the GNSS satellite in the global positioning navigation system relative to the center of the earth ellipsoid, and the vectors from all boundary points to the center of the earth ellipsoid, including: For each boundary point, the theoretical position of the GNSS satellite in the global positioning navigation system corresponding to the boundary point is obtained according to the direction of the incident signal at the boundary point, the theoretical height of the GNSS satellite in the global positioning navigation system relative to the center of the earth ellipsoid, and the vector from the boundary point to the center of the earth ellipsoid; The position range of the GNSS satellites in the global positioning navigation system is obtained according to all theoretical positions of the GNSS satellites in the global positioning navigation system corresponding to all boundary points.

4. The selection method according to claim 3, characterized in that: The direction of the incident signal at the boundary point is the direction from the theoretical position of the GNSS satellite in the global positioning navigation system to the boundary point; Obtaining the theoretical position of the GNSS satellite in the global positioning navigation system corresponding to the boundary point according to the direction of the incident signal at the boundary point, the theoretical height of the GNSS satellite in the global positioning navigation system relative to the center of the earth ellipsoid, and the vector from the boundary point to the center of the earth ellipsoid, including: In a triangle established with the theoretical position of the GNSS satellite in the global positioning navigation system, the boundary point and the center of the earth ellipsoid, the triangle is solved according to the direction from the theoretical position of the GNSS satellite in the global positioning navigation system to the boundary point, the vector from the boundary point to the center of the earth ellipsoid and the theoretical height of the GNSS satellite in the global positioning navigation system relative to the center of the earth ellipsoid to obtain the theoretical position of the GNSS satellite in the global positioning navigation system corresponding to the boundary point.

5. The selection method according to claim 3, characterized in that: After obtaining the position range of the GNSS satellites in the global positioning navigation system, the selection method further includes: The position range is converted into a theoretical altitude angle range and a theoretical azimuth angle range based on the target GNSS-R satellite.

6. The selection method according to claim 5, characterized in that: The selection method also includes: In the global positioning navigation system, a GNSS satellite is selected whose actual altitude angle relative to the target GNSS-R satellite is within the altitude angle range and whose actual azimuth angle relative to the target GNSS-R satellite is within the azimuth angle range.

7. The selection method according to claim 4, characterized in that: The theoretical height of the GNSS satellite in the global positioning navigation system relative to the center of the earth ellipsoid is equal to the sum of the theoretical orbital height of the GNSS satellite in the global positioning navigation system and the radius of the earth.

8. The selection method according to claim 1, characterized in that: The target GNSS-R satellites that are visible to the target observation area include: Determine the direction from the center of the target observation area to at least one GNSS-R satellite, the direction from the center of the target observation area to each GNSS-R satellite being the direction of the GNSS-R satellite; Determine at least one second angle according to the direction of at least one GNSS-R satellite and the normal vector of the center point of the target observation area, wherein the second angle is the angle between the direction of the GNSS-R satellite and the normal vector of the center point of the target observation area, and the normal vector of the center point of the target observation area is the normal vector of the center point of the target observation area on the surface of the earth ellipsoid; A GNSS-R satellite satisfying a second angle less than 90 degrees is selected from at least one GNSS-R satellite as the target GNSS-R satellite.

9. The selection method according to claim 1, characterized in that: The method for determining the target observation area includes: Identify all boundary points; The target observation area is determined based on the coordinates of all boundary points.

10. The selection method according to claim 1, characterized in that: After selecting a GNSS satellite whose actual position is within a specified position range of the global positioning navigation system in the global positioning navigation system, the selection method further includes: The target GNSS-R satellite is made to receive and process the signal from the selected GNSS satellite in the global positioning navigation system to realize the detection of the target observation area.

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