A method and apparatus for computing globally visible satellites

Abstract

This invention discloses a method for calculating visible satellites globally. Step S10: Divide the Earth into multiple regions. Step S20: Calculate the visible satellites within each region; the visible satellites for any point on Earth are those belonging to the region to which that point belongs. Step S20 includes: calculating the projection point (nadir point) of each satellite on Earth based on satellite ephemeris; calculating the visible angle range of each satellite on Earth based on its orbital altitude and nadir point; obtaining the visible range of each satellite based on the latitude and longitude of its nadir point and the angle of its visible range on Earth; selecting all satellites within the visible range for each region as the visible satellites within that region; if the visible range of a satellite completely or partially covers a region, then that satellite is considered a visible satellite within that region. The technical advantage of this invention is that it can quickly provide visible satellites for all locations globally, while maintaining low computational complexity.

Description

Technical Field

[0001] This invention relates to a method for satellite visibility analysis. Background Technology

[0002] Satellite visibility calculation is an essential algorithm in GNSS (Global Navigation Satellite System) receivers, used to calculate the visible satellites at a given location at a given time. A satellite receiver at a given location may be covered by zero, one, or more satellites at a given time. If the receiver can receive satellite signals and establish communication links with these satellites, then these satellites are the visible satellites at that location at that time.

[0003] Satellite visibility analysis typically employs the method of calculating satellite elevation angles, with the following steps: First, calculate the satellite's position in the sky at the current moment based on the satellite ephemeris. Then, calculate the elevation angle of the satellite at a given location and identify satellites with elevation angles within a certain range (e.g., greater than 5°) as visible satellites at that location.

[0004] In some scenarios, it is necessary to analyze satellite visibility over a global area. If satellite elevation angle is calculated, it would require traversing multiple locations worldwide to calculate the elevation angle of all satellites, resulting in extremely high computational complexity. This places high demands on the computing resources and response speed of the hardware. Summary of the Invention

[0005] The technical problem to be solved by this invention is: how to reduce computational complexity while satisfying the requirements of satellite visibility analysis in a global region.

[0006] To address the aforementioned technical problems, this invention proposes a method for calculating visible satellites globally, comprising the following steps: Step S10: Divide the Earth into multiple regions. Step S20: Calculate the visible satellites within each region; the visible satellites for any point on Earth are those belonging to the region to which that point belongs.

[0007] Furthermore, in step S10, the Earth is divided into multiple grid regions according to longitude and latitude, and each grid region is roughly rectangular.

[0008] Preferably, in step S10, the Earth is divided into regions at equal intervals according to longitude and at equal intervals according to latitude, thereby obtaining multiple regions.

[0009] Preferably, in step S10, the Earth is divided into regions at equal intervals according to longitude and at unequal intervals according to latitude—the lower the latitude, the smaller the interval between latitude divisions; the higher the latitude, the larger the interval between latitude divisions; thus, multiple regions are obtained.

[0010] Furthermore, in step S20, multiple points are taken in each region. First, the position of the satellite in the sky at the current time is calculated based on the satellite ephemeris. Then, the elevation angle of the satellite at that point is calculated, and satellites with elevation angles within a certain range are taken as visible satellites at that point. The union of the visible satellites at all points in each region is taken as the visible satellites in that region.

[0011] Preferably, in step S20, if the region is roughly rectangular, then the four vertices of the rectangular region are selected.

[0012] Further, step S20 includes the following steps: Step S21: Calculate the projection point of each satellite on Earth, i.e., the nadir point, based on the satellite ephemeris. Step S22: Calculate the visible angle range of each satellite on Earth based on its orbital altitude and nadir point, and then obtain the visible range of the satellite based on the latitude and longitude of its nadir point and the angle of its visible range on Earth. Step S23: Select all satellites within the visible range for each region as visible satellites within that region; if the visible range of a satellite completely or partially covers a region, then that satellite is considered a visible satellite within that region.

[0013] Furthermore, in step S21, the position coordinates of each satellite are first calculated based on the satellite ephemeris, and the position coordinates of the satellite are converted into latitude, longitude and altitude. The obtained latitude and longitude are the projection points of the satellite on the Earth, i.e., the sub-satellite points.

[0014] Further, in step S22, let R represent the Earth's radius, H represent the orbital altitude of a satellite, and the visible angle range of the satellite on Earth.

[0015] This invention also proposes an apparatus for calculating visible satellites across all regions of the globe, comprising a region division unit and a calculation unit. The region division unit is used to divide the Earth into multiple regions. The calculation unit is used to calculate the visible satellites within each region, and the visible satellites for any point on Earth are those belonging to the region to which that point belongs.

[0016] The technical advantage achieved by this invention is that it can quickly provide visible satellite information for all locations around the world, while having low computational complexity and low requirements for hardware computing resources and response speed. Attached Figure Description

[0017] Figure 1This is a flowchart illustrating the method for calculating visible satellites in all regions of the globe proposed in this invention.

[0018] Figure 2 This is an exemplary diagram illustrating the division of the Earth into multiple regions.

[0019] Figure 3 This is a flowchart illustrating the second calculation method in step S20.

[0020] Figure 4 This is a schematic diagram showing the visible range of a certain satellite on Earth at a certain moment.

[0021] Figure 5 This is a schematic diagram showing the visible angle range of a certain satellite on Earth at a certain moment.

[0022] Figure 6 This is a schematic diagram of the device proposed in this invention for calculating visible satellites in all regions of the globe.

[0023] Figure 7 This is a schematic diagram of the internal structure of the computing unit 20.

[0024] The following are the annotations in the figure: 10 is the area division unit, 20 is the calculation unit, 21 is the sub-satellite point calculation unit, 22 is the visible range calculation unit, and 23 is the area calculation unit. Detailed Implementation

[0025] Please see Figure 1 The method for calculating visible satellites in all regions of the globe proposed in this invention includes the following steps.

[0026] Step S10: Divide the Earth into multiple regions according to certain rules. For example, divide the Earth into multiple grid regions according to longitude and latitude. Each grid region is a curved surface, which can be approximated as a rectangle on a plane. The specific division method can be adjusted according to the actual situation. For example, divide the Earth into equal intervals according to longitude and equal intervals according to latitude to obtain multiple regions. Figure 2 Another example of this approach is to divide the Earth into regions at equal intervals of longitude (defined by dashed lines) and at unequal intervals of latitude (defined by both solid and dashed lines). Lower latitude regions have smaller latitudinal intervals, while higher latitude regions have larger intervals, resulting in multiple regions. This division is based on the fact that there are more visible satellites in lower latitude regions than in higher latitude regions.

[0027] Step S20: Calculate the visible satellites within each region. Any point on Earth must belong to a certain region defined in step S10, so the visible satellites for that point are the visible satellites of the region to which that point belongs.

[0028] The first calculation method in step S20 is as follows: Multiple points are taken within each region, for example, the four vertices of a rectangle within each roughly rectangular region. The visible satellites at each point are calculated using the elevation angle calculation method. The union of the visible satellites at all points within each region is taken as the visible satellites within that region. This method requires traversing and calculating the elevation angles of all satellites at each point, which typically involves a large amount of computation, but offers high accuracy.

[0029] Please see Figure 3 The second calculation method of step S20 includes the following steps.

[0030] Step S21: Calculate the projection point of each satellite on Earth, i.e., the subsatellite point, based on the satellite ephemeris. For example, first calculate the position coordinates of each satellite based on the satellite ephemeris, then convert the satellite position coordinates into latitude, longitude, and altitude. The obtained latitude and longitude are the projection point of the satellite on Earth, i.e., the subsatellite point.

[0031] Step S22: Calculate the visible angle range of each satellite on Earth based on its orbital altitude and nadir point. Figure 4 This shows the visible range P of a certain satellite SV on Earth at a certain moment. This visible range P is a curved surface, which can be approximated as a circle on a plane. Please refer to [link / reference]. Figure 5 Let P be the intersection of the line connecting satellite SV and the Earth's center O with the Earth's surface. Point P is the point below the satellite on Earth. Let R represent the Earth's radius and H represent the satellite's orbital altitude. Then the range of the satellite's visible angle on Earth is... The viewing angle range θ is as follows Figure 5 As shown. Then, based on the latitude and longitude of the nadir point of each satellite and the angle of its visible range on Earth, the visible range of that satellite can be obtained.

[0032] Step S23: Select all satellites within the visible range for each region as visible satellites within that region. This means that if the visible range of a satellite completely covers a region, then that satellite is considered a visible satellite within that region; if the visible range of a satellite partially covers a region, then that satellite is also considered a visible satellite within that region.

[0033] The two calculation methods in step S20 are both coarse algorithms compared to calculating visible satellites overhead based on the actual satellite receiver position, but they have lower computational complexity, faster calculation speed, and lower requirements for computing resources. Both methods are suitable for sending corresponding visible satellite ephemeris data when the AGNSS (Assisted Global Navigation Satellite System) server requests it from the satellite receiver. Furthermore, by adjusting the size of the grid area division in step S10, a balance can be struck between computational complexity and result accuracy. Under the same conditions, the second calculation method has lower computational complexity than the first, but correspondingly lower accuracy.

[0034] Please see Figure 6 The device proposed in this invention for calculating visible satellites in all regions of the world includes a region division unit 10 and a calculation unit 20. Figure 6 The device shown corresponds to Figure 1 The method shown.

[0035] The region division unit 10 is used to divide the Earth into multiple regions according to certain rules.

[0036] The computing unit 20 is used to calculate the visible satellites within each region. The visible satellites for any point on Earth are those for the region to which that point belongs.

[0037] Please see Figure 7 The calculation unit 20 further includes a sub-satellite point calculation unit 21, a visible range calculation unit 22, and a region calculation unit 23. Figure 7 The structure shown corresponds to Figure 3 The process is shown below.

[0038] The nadir point calculation unit 21 is used to calculate the projection point of each satellite on Earth, i.e., the nadir point, based on the satellite ephemeris.

[0039] The visible range calculation unit 22 is used to calculate the visible range of each satellite on Earth based on the orbital altitude and nadir point of each satellite, and then obtain the visible range of the satellite based on the latitude and longitude of the nadir point of each satellite and the angle of the visible range of the satellite on Earth.

[0040] The region calculation unit 23 is used to select all satellites within the visible range for each region as visible satellites within that region. That is, if the visible range of a satellite completely or partially covers a region, then that satellite is considered a visible satellite within that region.

[0041] This invention, by dividing the Earth into regions, can quickly provide a list of visible satellites for all locations globally. Specifically, the second algorithm in step S20 calculates the visible range of satellites based on their projection points on Earth and their orbital altitudes, thus obtaining the visible satellite range for all regions globally. This significantly reduces the computational complexity of calculating visible satellites worldwide.

[0042] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for calculating globally visible satellites, characterized in that, Includes the following steps; Step S10: Divide the Earth into multiple grid regions according to longitude and latitude, each grid region being approximately rectangular; Step S20: Calculate the visible satellites in each grid area by calculating the satellite elevation angle or the satellite visibility range. The visible satellites at any point on Earth are the visible satellites in the grid area to which that point belongs. The method for calculating the visible satellites within each grid area specifically includes: taking multiple points within each grid area, first calculating the current position of the satellite in the sky based on the satellite ephemeris, then calculating the elevation angle of the satellite at that point, and taking satellites with elevation angles within a certain range as visible satellites at that point, and taking the union of the visible satellites at all points within each grid area as the visible satellites within that grid area; The method for calculating the visible satellite range specifically includes the following steps: Step S21: Calculate the projection point of each satellite on Earth, i.e., the nadir point, based on the satellite ephemeris; Step S22: Calculate the visible angle range of each satellite on Earth based on its orbital altitude and nadir point, and then obtain the visible range of the satellite based on the latitude and longitude of its nadir point and the angle of its visible range on Earth; Step S23: Select all satellites within the visible range of each grid area as visible satellites within that grid area; If the visible range of a satellite completely or partially covers a grid area, then that satellite is considered a visible satellite within that grid area.

2. The method for calculating globally visible satellites according to claim 1, characterized in that, In step S10, the Earth is divided into regions at equal intervals according to longitude and at equal intervals according to latitude, thereby obtaining multiple regions.

3. The method for calculating globally visible satellites according to claim 2, characterized in that, In step S10, the Earth is divided into regions at equal intervals of longitude and at unequal intervals of latitude—the lower the latitude, the smaller the interval between latitude divisions; the higher the latitude, the larger the interval between latitude divisions; thus, multiple regions are obtained.

4. The method for calculating globally visible satellites according to claim 1, characterized in that, In step S20, if the region is roughly rectangular, then the four vertices of the rectangular region are selected.

5. The method for calculating globally visible satellites according to claim 1, characterized in that, In step S21, the position coordinates of each satellite are first calculated based on the satellite ephemeris. The position coordinates of the satellite are then converted into latitude, longitude, and altitude. The obtained latitude and longitude are the projection points of the satellite on the Earth, i.e., the sub-satellite points.

6. The method for calculating globally visible satellites according to claim 1, characterized in that, In step S22, let R represent the Earth's radius, H represent the orbital altitude of a satellite, and the visible angular range of the satellite within the Earth's range. .

7. An apparatus for calculating visible satellites in all regions of the globe, characterized in that, Includes regional division units and calculation units; The region division unit is used to divide the Earth into multiple grid regions according to longitude and latitude, and each grid region is roughly rectangular; The computing unit is used to calculate the visible satellites in each grid area by calculating the satellite elevation angle or the satellite visible range. The visible satellites at any point on Earth are the visible satellites in the grid area to which that point belongs. The method for calculating the visible satellites within each grid area specifically includes: taking multiple points within each grid area, first calculating the current position of the satellite in the sky based on the satellite ephemeris, then calculating the elevation angle of the satellite at that point, and taking satellites with elevation angles within a certain range as visible satellites at that point, and taking the union of the visible satellites at all points within each grid area as the visible satellites within that grid area; The method for calculating the visible satellite range specifically includes the following steps: Step S21: Calculate the projection point of each satellite on Earth, i.e., the nadir point, based on the satellite ephemeris; Step S22: Calculate the visible angle range of each satellite on Earth based on its orbital altitude and nadir point, and then obtain the visible range of the satellite based on the latitude and longitude of its nadir point and the angle of its visible range on Earth; Step S23: Select all satellites within the visible range of each grid area as visible satellites within that grid area; If the visible range of a satellite completely or partially covers a grid area, then that satellite is considered a visible satellite within that grid area.

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