Doppler frequency shift positioning method, device, equipment and medium based on low-orbit satellite

Abstract

The present invention discloses a Doppler frequency shift positioning method, device, equipment and medium based on low-orbit satellites. The method comprises the following steps: receiving visible low-orbit satellite ephemeris data; calculating the position of each low-orbit satellite based on the received satellite ephemeris data; calculating the sub-satellite point according to the satellite position, and determining its visible range with the sub-satellite point as the center; taking the intersection of the visible ranges of multiple low-orbit satellites, and evenly taking points within the intersection range as the initial value points to be selected for positioning; taking each initial value point to be selected as the initial value point for positioning of the Doppler frequency shift observation equation, using the least square method to calculate the user position, and recording the size of the positioning residual; traversing to obtain the minimum value of the positioning residual of all the initial value points to be selected, judging whether the minimum value of the residual is less than the residual threshold, and if it is less than the residual threshold, convergence is successful, and taking the user position corresponding to the minimum value of the residual as the user's positioning result. The present invention reduces the search range of the initial value and the number of searches, thereby accelerating the iterative convergence speed and thus accelerating the positioning speed.

Description

Technical Field

[0001] The present invention belongs to the field of satellite positioning technology, and in particular relates to a Doppler frequency shift positioning method, device, equipment and medium based on a low-orbit satellite. Background Art

[0002] The low-orbit satellite communication system is a discontinuous signal. Based on its special signal transmission method, the traditional GNSS positioning method that requires continuous pseudo-range observation is no longer applicable. Low-orbit satellites move quickly relative to the ground, have large Doppler frequency shift, and have good Doppler observability. Positioning technology based on Doppler characteristics is very suitable for low-orbit satellite positioning systems, so low-orbit satellite systems use Doppler positioning.

[0003] In the Doppler frequency-based positioning method for ground terminals, the least squares algorithm is usually used to solve the position, which requires consideration of the initial value problem of iterative calculation. Since low-orbit satellites are generally distributed in orbits between 500 and 2000 km, the orbital altitude is relatively low, and the error ratio relative to the radius of the earth is relatively high, it is generally necessary to obtain initial coordinates of a certain accuracy in order to perform least squares iteration to obtain the solution result. Unlike GNSS positioning, even if the initial value is set to the center of the earth, it is not possible to quickly iterate and converge to obtain the solution result. If Doppler positioning still uses the center of the earth as the initial value of the iteration, since the orbital altitude of the low-orbit satellite is much smaller than the radius of the earth, the error of the linearization result is large, which will cause the iteration with the center of the earth as the initial value to fail to converge. This shows the importance of initial value selection.

[0004] At present, the main method for determining the initial positioning value is the large-area grid search method, which requires searching an area of ​​millions of square kilometers, has a large amount of computational data, and has a large initial value error and slow convergence speed. Summary of the invention

[0005] The present invention provides a Doppler frequency shift positioning method, device, equipment and medium based on a low-orbit satellite, which accelerates the iterative convergence speed and further accelerates the positioning speed by narrowing the search range of the initial value and reducing the number of searches.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0007] A Doppler frequency shift positioning method based on a low-orbit satellite, comprising:

[0008] Determine multiple low-orbit satellites visible to the user and receive ephemeris data of each low-orbit satellite;

[0009] Calculating the position of each low-orbit satellite based on the received satellite ephemeris data;

[0010] For each low-orbit satellite, the sub-satellite point is calculated according to its position, and its visible range is determined with its sub-satellite point as the center;

[0011] Take the intersection of the visible ranges of multiple low-orbit satellites, and evenly select points within the intersection range as the initial value points to be selected for positioning;

[0012] Each of the selected initial value points is used as the initial value for iterative calculation when the Doppler frequency shift observation equation is solved by the least square method to calculate the user position, and the size of the positioning residual is recorded;

[0013] Traverse and obtain the minimum positioning residual value of all the initial value points to be selected, and determine whether the minimum residual value is less than the residual threshold. If it is less than the residual threshold, convergence is successful, and the user position corresponding to the minimum residual value is taken as the user's positioning result.

[0014] Furthermore, the position of each low-orbit satellite is calculated as follows:

[0015]

[0016] In the formula, represents the three-dimensional coordinates of the satellite in the Earth-centered Earth-fixed rectangular coordinate system at epoch k, which is the position to be calculated; , , They represent the coordinates of the satellite in the orbital plane at epoch k, the longitude of the satellite's ascending node, and the corrected orbital inclination of the satellite. , , All are obtained from satellite ephemeris data.

[0017] Furthermore, the sub-satellite point is calculated according to the satellite position:

[0018] The low-orbit satellite position will be calculated, that is, the three-dimensional coordinates in the Earth-centered Earth-fixed rectangular coordinate system , converted to coordinates in the geodetic coordinate system :

[0019]

[0020] in, are latitude, longitude and altitude respectively, For point The radius of the circle of is the first eccentricity of the Earth ellipsoid, For the earth dimension;

[0021] Get elevation , get the satellite's sub-satellite coordinates .

[0022] Furthermore, the satellite visible range is determined with the satellite subsatellite point as the center, specifically:

[0023] According to the coordinates of the low-orbit satellite geodetic coordinate system Determine its elevation ;

[0024] Based on satellite altitude Calculate the satellite's visible half angle :

[0025]

[0026] Where R is the radius of the earth, is the cut-off altitude angle;

[0027] Based on the viewing half angle Calculate the chord length r, and use r as the radius of the inscribed circle of the rectangle dividing the visible range;

[0028]

[0029] Taking the subsatellite point as the center point, determine the length of the visible range rectangle along the longitude and latitude directions:

[0030] ,

[0031] In the formula, is the length of the visible range rectangle along the longitude direction, The length of the visible range rectangle along the latitude direction.

[0032] Furthermore, the method of evenly selecting points within the intersection range is:

[0033] Since the visible range of each low-orbit satellite is a rectangle along the longitude and latitude directions, the intersection of the visible ranges of multiple low-orbit satellites is also a rectangle, which is recorded as the intersection range rectangle;

[0034] The intersection range rectangle is divided into a plurality of rectangular grids of the same preset size in sequence, with its center as the origin and extending in all directions, until all the intersection range rectangles are divided into a certain grid;

[0035] A preset corner point of each grid is used as the initial value point to be selected for positioning.

[0036] Furthermore, the Doppler frequency shift observation method is specifically as follows:

[0037]

[0038] In the formula, is the observed value of Doppler frequency shift; The unknowns to be determined include the user's location and user receiver clock deviation ; is the frequency measurement error; The frequency of the satellite's transmitted signal; is the satellite motion speed; is the satellite position.

[0039] A Doppler frequency shift positioning method and device based on a low-orbit satellite, comprising:

[0040] A data receiving module is used to: receive ephemeris data of multiple visible low-orbit satellites;

[0041] The satellite position calculation module is used to calculate the satellite position based on the ephemeris data of each satellite;

[0042] The satellite visible range determination module is used to: for each low-orbit satellite, calculate the sub-satellite point according to its position, and determine its visible range with its sub-satellite point as the center;

[0043] The module for selecting the initial value points to be selected is used to: obtain the intersection of the visible ranges of multiple low-orbit satellites, and evenly select points within the intersection range as the initial value points to be selected for positioning;

[0044] The positioning calculation module is used to: use each of the selected initial value points as the initial value for iterative calculation when solving the Doppler frequency shift observation equation using the least square method to calculate the user position, and record the size of the positioning residual;

[0045] The positioning result determination module is used to: traverse and obtain the minimum positioning residual value of all the initial value points to be selected, determine whether the minimum residual value is less than the residual threshold, if it is less than the residual threshold, convergence is successful, and take the user position corresponding to the minimum residual value as the user's positioning result.

[0046] An electronic device comprises a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor implements any of the above-mentioned Doppler frequency shift positioning methods based on low-orbit satellites.

[0047] A computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the Doppler frequency shift positioning method based on a low-orbit satellite described in any one of the above items is implemented.

[0048] Beneficial Effects

[0049] The present invention determines the visible range of a single satellite through the sub-satellite point, then takes the intersection of the visible ranges of multiple satellites as the initial value area to be selected for positioning, and then takes points in the area and compares the residuals to determine the initial value points of Doppler positioning. Compared with the traditional method, the search range of the initial value is greatly narrowed, the number of searches is reduced, thereby accelerating the iterative convergence speed and further accelerating the positioning speed.

[0050] Experiments show that using the same set of data and the same search spacing, the number of searches in a large area is 56 times, while the number of searches for this method is 12 times, a reduction of 78%, with a significant acceleration effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 is a schematic diagram of the method described in an embodiment of the present invention;

[0052] Figure 2 This is a schematic diagram of the visual range of a low-orbit satellite according to an embodiment of the present invention;

[0053] Figure 3 is a schematic diagram of a visible range rectangle of a low-orbit satellite according to an embodiment of the present invention;

[0054] Figure 4 It is a schematic diagram of the intersection of the visible range rectangles of the low-orbit satellite according to an embodiment of the present invention. DETAILED DESCRIPTION

[0055] The following is a detailed description of an embodiment of the present invention. This embodiment is based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process to further explain the technical solution of the present invention.

[0056] Example 1

[0057] This embodiment provides a Doppler frequency shift positioning method based on a low-orbit satellite. Figure 1 As shown, including:

[0058] Step 1: determine multiple low-orbit satellites visible to the user and receive ephemeris data of each low-orbit satellite.

[0059] Step 2: Calculate the position of each low-orbit satellite based on the received satellite ephemeris data:

[0060]

[0061] In the formula, represents the three-dimensional coordinates of the satellite in the Earth-centered Earth-fixed rectangular coordinate system at epoch k, which is the position to be calculated; , , They represent the coordinates of the satellite in the orbital plane at epoch k, the longitude of the satellite's ascending node, and the corrected orbital inclination of the satellite. , , Both can be obtained from satellite ephemeris data.

[0062] Step 3: For each low-orbit satellite, calculate the sub-satellite point according to its position, and determine its visible range with its sub-satellite point as the center.

[0063] The sub-satellite point refers to the intersection of the line connecting the satellite and the center of the earth on the surface of the earth, that is, the point directly below the satellite projected onto the ground. Step 3 includes:

[0064] Step 3.1, calculate the sub-satellite point according to the satellite position, specifically:

[0065] Step 3.1.1: The calculated low-orbit satellite position, i.e., the three-dimensional coordinates in the Earth-centered Earth-fixed rectangular coordinate system , converted to coordinates in the geodetic coordinate system :

[0066]

[0067] in, are latitude, longitude and altitude respectively, For point The radius of the circle of is the first eccentricity of the Earth ellipsoid; It is the geodetic dimension. When a point on the earth is projected onto the earth's ellipsoid, the angle between the normal direction of the projection point and the equatorial plane is the geodetic dimension of the point.

[0068] Step 3.1.2, get the elevation , get the satellite's sub-satellite coordinates .

[0069] Step 3.2, determine the visible range of the satellite with the satellite subsatellite point as the center, specifically:

[0070] Step 3.2.1, based on the coordinates of the low-orbit satellite geodetic coordinate system Determine its elevation ;

[0071] The visible range of the satellite can be determined by the user's response to the central half angle of the satellite visible area relative to the earth, assuming that the earth is a uniform sphere as follows: Figure 2 As shown, the elevation Calculate the satellite's visible half angle :

[0072]

[0073] Where R is the radius of the earth, is the satellite altitude, is the cut-off height angle, and its empirical value is 5°~10°;

[0074] Step 3.2.2, based on the viewing half angle Calculate the chord length r, and use r as the radius of the inscribed circle of the rectangle dividing the visible range;

[0075]

[0076] Step 3.2.3, point below the star As the center point, Figure 3 As shown, the length of the visible range rectangle is determined along the longitude and latitude directions:

[0077] ,

[0078] In the formula, is the length of the visible range rectangle along the longitude direction, The length of the visible range rectangle along the latitude direction.

[0079] Step 4: Take the intersection of the visible ranges of multiple low-orbit satellites and evenly select points within the intersection range as the initial value points to be selected for positioning.

[0080] The method of evenly selecting points within the intersection range in this embodiment is:

[0081] Step 4.1, based on the fact that the visible range of each low-orbit satellite is a rectangle along the longitude and latitude directions, the intersection of the visible ranges of multiple low-orbit satellites is also a rectangle, which is recorded as the intersection range rectangle;

[0082] Step 4.2, the intersection range rectangle is divided into a number of rectangular grids of the same preset size in sequence, with its center as the origin, until all the intersection range rectangles are divided into a certain grid (when the edge area of ​​the edge intersection range rectangle is not enough to be divided into an integer number of grids, the range of the intersection range rectangle is appropriately increased); Figure 4 As shown;

[0083] Step 4.3, use the upper left corner point of each grid as the initial value point to be selected for positioning.

[0084] Step 5: Use each of the selected initial value points as the initial value for iterative calculation when solving the Doppler frequency shift observation equation using the least squares method to calculate the user position, and record the positioning residual size accordingly.

[0085] The Doppler frequency shift observation equation is:

[0086]

[0087] In the formula, is the Doppler frequency shift observation value obtained by the user receiver; user position and user receiver clock deviation To seek the unknown; is the frequency measurement error; The frequency of the satellite's transmitted signal; is the satellite motion speed; is the satellite position.

[0088] Step 6: traverse and obtain the minimum positioning residual value of all the initial value points to be selected, and determine whether the minimum residual value is less than the residual threshold. If it is less than the residual threshold, convergence is successful, and the user position corresponding to the minimum residual value is taken as the user's positioning result.

[0089] The residual threshold value can be obtained through multiple positioning tests, and the empirical value is 1.0e-3. Only when the minimum residual value is less than the threshold, that is, less than 1.0e-3, is convergence successful and positioning successful. Otherwise, positioning is considered a failure.

[0090] When solving the user positioning in the next epoch, the positioning result obtained by convergence in this epoch is used as the initial value.

[0091] Example 2

[0092] This embodiment provides a Doppler frequency shift positioning device based on a low-orbit satellite, including:

[0093] A data receiving module is used to: receive ephemeris data of multiple visible low-orbit satellites;

[0094] The satellite position calculation module is used to calculate the satellite position based on the ephemeris data of each satellite;

[0095] The satellite visible range determination module is used to: for each low-orbit satellite, calculate the sub-satellite point according to its position, and determine its visible range with its sub-satellite point as the center;

[0096] The module for selecting the initial value points to be selected is used to: obtain the intersection of the visible ranges of multiple low-orbit satellites, and evenly select points within the intersection range as the initial value points to be selected for positioning;

[0097] The initial value point selection module is used to: substitute each candidate initial value point into the least squares algorithm in turn, record the size of its residual, and then select the candidate initial value point corresponding to the minimum residual value;

[0098] The positioning calculation module is used to: use the candidate initial value point selected by the positioning initial value point selection module as the positioning initial value point of the Doppler frequency shift observation equation, and calculate the user position using the least square method.

[0099] The working principles and implementation methods of the above modules in the positioning device of this embodiment are the same as those in Embodiment 1, and will not be repeated here.

[0100] Example 3

[0101] This embodiment provides an electronic device, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor implements the Doppler frequency shift positioning method based on low-orbit satellites described in Example 1.

[0102] Example 4

[0103] This embodiment provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the Doppler frequency shift positioning method based on a low-orbit satellite described in Embodiment 1 is implemented.

[0104] The above embodiments are preferred embodiments of the present application. Ordinary technicians in this field can also make various changes or improvements on this basis. Without departing from the overall concept of the present application, these changes or improvements should fall within the scope of protection required by the present application.

Claims

1. A Doppler frequency shift positioning method based on low-orbit satellites, It is characterized in that include: Determine multiple low-orbit satellites visible to the user and receive ephemeris data of each low-orbit satellite; Calculating the position of each low-orbit satellite based on the received satellite ephemeris data; For each low-orbit satellite, the sub-satellite point is calculated according to its position, and its visible range is determined with its sub-satellite point as the center; Among them, the calculation of the sub-satellite point according to the satellite position is specifically: The low-orbit satellite position will be calculated, that is, the three-dimensional coordinates in the Earth-centered Earth-fixed rectangular coordinate system , converted to coordinates in the geodetic coordinate system : ； in, are latitude, longitude and altitude respectively, For point The radius of the circle of is the first eccentricity of the Earth ellipsoid, For the earth dimension; Get elevation , get the satellite's sub-satellite coordinates ; The satellite visible range is determined with the satellite subsatellite point as the center, specifically: According to the coordinates of the low-orbit satellite geodetic coordinate system Determine its elevation ; Based on satellite altitude Calculate the satellite's visible half angle : ； Where R is the radius of the earth, is the cut-off height angle; Based on the viewing half angle Calculate the chord length r, and use r as the radius of the inscribed circle of the rectangle dividing the visible range; ； Taking the subsatellite point as the center point, determine the length of the visible range rectangle along the longitude and latitude directions: ， ； In the formula, is the length of the visible range rectangle along the longitude direction, is the length of the visible range rectangle along the latitude direction; Take the intersection of the visible ranges of multiple low-orbit satellites, and evenly select points within the intersection range as the initial value points to be selected for positioning; Each of the selected initial value points is used as the initial value for iterative calculation when the Doppler frequency shift observation equation is solved by the least square method to calculate the user position, and the size of the positioning residual is recorded; Traverse and obtain the minimum positioning residual value of all the initial value points to be selected, and determine whether the minimum residual value is less than the residual threshold. If it is less than the residual threshold, convergence is successful, and the user position corresponding to the minimum residual value is taken as the user's positioning result.

2. The Doppler frequency shift positioning method based on low-orbit satellite according to claim 1, It is characterized in that The specific calculation of the position of each low-orbit satellite is: ； In the formula, represents the three-dimensional coordinates of the satellite in the Earth-centered Earth-fixed rectangular coordinate system at epoch k, which is the position to be calculated; , , They represent the coordinates of the satellite in the orbital plane at epoch k, the longitude of the satellite's ascending node, and the corrected orbital inclination of the satellite. , , All are obtained from satellite ephemeris data.

3. The Doppler frequency shift positioning method based on low-orbit satellite according to claim 1, It is characterized in that The method of evenly selecting points within the intersection range is: Since the visible range of each low-orbit satellite is a rectangle along the longitude and latitude directions, the intersection of the visible ranges of multiple low-orbit satellites is also a rectangle, which is recorded as the intersection range rectangle; The intersection range rectangle is divided into a plurality of rectangular grids of the same preset size in sequence, with its center as the origin and extending in all directions, until all the intersection range rectangles are divided into a certain grid; A preset corner point of each grid is used as the initial value point to be selected for positioning.

4. The Doppler frequency shift positioning method based on low-orbit satellite according to claim 1, It is characterized in that The Doppler frequency shift observation method is specifically as follows: ； In the formula, is the observed value of Doppler frequency shift; The unknowns to be determined include the user's location and user receiver clock deviation ; is the frequency measurement error; The frequency of the satellite's transmitted signal; is the satellite motion speed; is the satellite position.

5. A Doppler frequency shift positioning device based on low-orbit satellites, It is characterized in that include: A data receiving module is used to: receive ephemeris data of multiple visible low-orbit satellites; The satellite position calculation module is used to calculate the satellite position based on the ephemeris data of each satellite; The satellite visible range determination module is used to: for each low-orbit satellite, calculate the sub-satellite point according to its position, and determine its visible range with its sub-satellite point as the center; Among them, the calculation of the sub-satellite point according to the satellite position is specifically: The low-orbit satellite position will be calculated, that is, the three-dimensional coordinates in the Earth-centered Earth-fixed rectangular coordinate system , converted to coordinates in the geodetic coordinate system : ； in, are latitude, longitude and altitude respectively, For point The radius of the circle of is the first eccentricity of the Earth ellipsoid, For the earth dimension; Get elevation , get the satellite's sub-satellite coordinates ; The satellite visible range is determined with the satellite subsatellite point as the center, specifically: According to the coordinates of the low-orbit satellite geodetic coordinate system Determine its elevation ; Based on satellite altitude Calculate the satellite's visible half angle : ； Where R is the radius of the earth, is the cut-off height angle; Based on the viewing half angle Calculate the chord length r, and use r as the radius of the inscribed circle of the rectangle dividing the visible range; ； Taking the subsatellite point as the center point, determine the length of the visible range rectangle along the longitude and latitude directions: ， ； In the formula, is the length of the visible range rectangle along the longitude direction, is the length of the visible range rectangle along the latitude direction; The module for selecting the initial value points to be selected is used to: obtain the intersection of the visible ranges of multiple low-orbit satellites, and evenly select points within the intersection range as the initial value points to be selected for positioning; The positioning calculation module is used to: use each of the selected initial value points as the initial value for iterative calculation when solving the Doppler frequency shift observation equation using the least square method to calculate the user position, and record the size of the positioning residual; The positioning result determination module is used to: traverse and obtain the minimum positioning residual value of all the initial value points to be selected, determine whether the minimum residual value is less than the residual threshold, if it is less than the residual threshold, convergence is successful, and take the user position corresponding to the minimum residual value as the user's positioning result.

6. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, It is characterized in that When the computer program is executed by the processor, the processor implements the method according to any one of claims 1 to 4.

7. A computer-readable storage medium having a computer program stored thereon, It is characterized in that When the computer program is executed by a processor, the method according to any one of claims 1 to 4 is implemented.

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