Satellite laser height measurement foot point positioning elevation error analysis method and device and medium

Abstract

The invention relates to a satellite laser height measurement foot point positioning elevation error analysis method and device and a medium, and belongs to the technical field of satellite surveying and mapping. The method comprises the steps that sensor data of a satellite sensor and discrete full-waveform data of laser sent by a satellite laser height indicator are acquired, a satellite laser distance measurement error model is established, and the satellite laser distance measurement error model is calculated; determining an influence error factor; the influence error factor comprises a laser ranging error; inputting the discrete full-waveform data into a satellite laser ranging error model to obtain a laser ranging error value of the laser ranging error; according to the sensor data and the laser ranging error value, a satellite laser foot point positioning elevation comprehensive error value is obtained; according to the method, the laser ranging error value can be calculated through the satellite laser ranging error model, so that the satellite laser footprint positioning elevation comprehensive error value can be obtained through the laser ranging error value and data detected by other sensors, terrain parameters in a laser footprint do not need to be input, and the usability of the model is improved.

Description

Technical Field

[0001] The present invention relates to the field of satellite detection technology, and in particular to a method, device, equipment and medium for analyzing elevation errors of satellite laser height measurement footpoint positioning. Background Art

[0002] Satellite laser altimetry, as an active remote sensing technology, provides a new means of satellite remote sensing observation for mankind. By measuring the round-trip time of the laser emitted by the laser, combined with the orbital position and attitude of the satellite platform, the elevation information of the target surface with decimeter or even centimeter accuracy can be calculated. It has been applied in the observation of the earth, the moon, Mars and other planets. After emitting laser, the full-waveform laser altimeter can receive the complete backscattered waveform of the target surface, which can not only obtain richer surface profile elevation information, but also can be used to quantitatively analyze the geometric and physical properties of the target surface. However, due to the influence of various error factors, the coordinates of the satellite laser altimetry footpoints inevitably contain errors. Establishing a satellite-borne laser altimetry error analysis model and quantitatively analyzing the elevation error value of the satellite-borne laser altimetry footpoint positioning will provide an important reference for the application of laser altimetry products.

[0003] In the prior art, ICESat / GLAS laser altimetry data and high-precision airborne laser point clouds were used to verify the accuracy of the established laser altimetry error analysis model. However, the laser altimetry error under large terrain slopes was not calculated and the model accuracy was not verified. At the same time, when the satellite-borne laser altimetry system is actually working, the laser pointing error and terrain slope factors will significantly affect the laser ranging accuracy. When analyzing the satellite-borne laser altimetry error based on all existing model methods, the terrain parameters in the laser footprint need to be input as known parameters. However, for satellite-borne laser altimetry points distributed around the world, it is currently difficult to obtain high-precision terrain parameters in their footprints, which will greatly reduce the availability of existing model methods.

[0004] Therefore, it is urgent to propose a method, device, equipment and medium for analyzing elevation errors of satellite laser altimetry footpoint positioning to solve the technical problem that the model in the prior art needs to input the terrain parameters in the laser footprint as known parameters, but the high-precision terrain parameters in the footprint are currently difficult to obtain, resulting in reduced model availability. Summary of the invention

[0005] In view of this, it is necessary to provide a satellite laser altimetry footpoint positioning elevation error analysis method, device, equipment and medium to solve the technical problem that the model in the prior art needs to input the terrain parameters in the laser footprint as known parameters, but the high-precision terrain parameters in the footprint are currently difficult to obtain, resulting in reduced model availability.

[0006] In order to solve the above problems, the present invention provides a method for analyzing the elevation error of a satellite laser altimetry footpoint positioning, comprising: Acquire sensor data of a satellite sensor and discrete full waveform data of a laser sent by a satellite laser altimeter, establish a satellite laser ranging error model, and determine influencing error factors; the influencing error factors include laser ranging errors; Inputting the discrete full waveform data into the satellite laser ranging error model to obtain a laser ranging error value of the laser ranging error; According to the sensor data and the laser ranging error value, a satellite laser foot point positioning elevation comprehensive error value is obtained.

[0007] In a possible implementation, establishing a satellite laser ranging error model includes: The discrete full waveform data is analyzed based on satellite laser altimetry echo theory to obtain a laser ranging error factor that affects the laser ranging error; A simulation calculation is performed based on the laser ranging error factor to establish a satellite laser ranging error model.

[0008] In a possible implementation, inputting the discrete full waveform data into the satellite laser ranging error model to obtain the laser ranging error value of the laser ranging error includes: Analyzing the discrete full waveform data to obtain the laser echo pulse width, the laser emission pulse width and the detector pulse response pulse width; The laser echo pulse width, the laser emission pulse width and the detector pulse response pulse width are calculated according to the timing variance calculation formula of the satellite laser ranging error model to obtain the satellite laser altimetry timing variance; The satellite laser ranging error variance is calculated according to the ranging error calculation formula of the satellite laser ranging error model to obtain the laser ranging error value of the laser ranging error.

[0009] In a possible implementation, the influencing error factors also include the laser optical axis pointing error, satellite attitude measurement error and satellite positioning error; the sensor data includes the three-axis angle between the laser optical axis and the laser measurement platform coordinate system, the satellite attitude angle, the satellite orbit position and the ranging distance; the satellite laser foot point positioning elevation comprehensive error value is obtained according to the sensor data and the laser ranging error value, including: Acquire a laser optical axis inward pointing error value of the laser optical axis inward pointing error, a satellite attitude measurement error value of the satellite attitude measurement error, and a satellite positioning error value of the satellite positioning error; Obtaining the laser foot point elevation according to the three-axis angle, the satellite attitude angle, the satellite orbit position and the ranging distance; According to the satellite laser altimetry foot point positioning elevation error comprehensive model, the laser ranging error value, the laser optical axis internal pointing error value, the satellite attitude measurement error value and the satellite positioning error value are calculated to obtain the satellite laser foot point positioning elevation comprehensive error value.

[0010] In a possible implementation, the timing variance calculation formula is:

[0011] In the formula, echo time center of gravity; is the laser echo pulse width; is the laser emission pulse width; is the pulse width of the detector pulse response; is the laser pointing angle; is the laser divergence angle; is the speed of light in a vacuum; is the height from the satellite to the earth’s surface; , , is the fitting parameter; is the photodetector noise factor; is the number of photons contained in the echo; is the sampling time resolution of the echo waveform; is the mean square pulse width of the echo; is the speckle signal-to-noise ratio.

[0012] In a possible implementation, the ranging error calculation formula is:

[0013] In the formula, is the speed of light in a vacuum; is the satellite laser altimetry timing variance.

[0014] In a possible implementation, the satellite laser altimetry footpoint positioning elevation error comprehensive model is:

[0015] , ,

[0016] In the formula, It is the comprehensive error value of satellite laser foot point positioning elevation; is the laser foot point elevation; Satellite orbital position x, y, z Measurements in the axial direction; The satellite orbital position after precise orbit determination x, y, z Positioning information in the axis direction; is the satellite orbital position x, y, z Satellite positioning error value in the axis direction; is the measured value of the satellite attitude angle; It is the three-axis attitude angle of the satellite after precise attitude determination; is the coordinates of the laser optical axis and the laser measurement platform x, y, z The measured value of the angle in the axial direction; is the coordinates of the laser optical axis and the laser measurement platform x, y, z The laser optical axis pointing error value of the angle in the axial direction; is the laser ranging error value.

[0017] On the other hand, the present invention also provides a satellite laser altimetry foot point positioning elevation error analysis device, comprising: A data acquisition module is used to acquire sensor data of a satellite sensor and discrete full waveform data of a laser sent by a satellite laser altimeter, establish a satellite laser ranging error model, and determine influencing error factors; the influencing error factors include laser ranging errors; An error value calculation module, used for inputting the discrete full waveform data into the satellite laser ranging error model to obtain a laser ranging error value of the laser ranging error; The elevation error calculation module is used to obtain the satellite laser foot point positioning elevation comprehensive error value according to the sensor data and the laser ranging error value.

[0018] On the other hand, an embodiment of the present invention discloses an electronic device, comprising: a processor, a memory, and a computer program stored in the memory and capable of running on the processor, wherein when the computer program is executed by the processor, each step of the above-mentioned satellite laser altimetry footpoint positioning elevation error analysis method embodiment is implemented.

[0019] On the other hand, an embodiment of the present invention discloses a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the various steps of the above-mentioned satellite laser altimetry footpoint positioning elevation error analysis method embodiment are implemented.

[0020] The beneficial effects of the present invention are as follows: sensor data of a satellite sensor and discrete full waveform data of a laser sent by a satellite laser altimeter are obtained, a satellite laser ranging error model is established, and an influencing error factor is determined; the influencing error factor includes a laser ranging error; the discrete full waveform data is input into the satellite laser ranging error model to obtain a laser ranging error value of the laser ranging error; according to the sensor data and the laser ranging error value, a satellite laser foot point positioning elevation comprehensive error value is obtained; the present invention can calculate the laser ranging error value through the satellite laser ranging error model, thereby obtaining the satellite laser foot point positioning elevation comprehensive error value through the laser ranging error value and data detected by other sensors, without the need to input terrain parameters in the laser footprint, thereby improving the availability of the model. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic flow chart of an embodiment of a method for analyzing elevation errors of satellite laser altimetry footpoint positioning provided by the present invention; Figure 2 A schematic diagram of the structure of an embodiment of the five coordinate frames provided by the present invention; Figure 3 A schematic structural diagram of an embodiment of the laser altimeter system provided by the present invention in which the laser altimeter is incident obliquely onto an inclined surface of the ground; Figure 4 For the present invention Figure 1 A schematic flow chart of an embodiment of step S102; Figure 5 A schematic diagram of an embodiment of the structure of experimental data collected in a certain region provided by the present invention; Figure 6 A coordinate schematic diagram of an embodiment of a scatter diagram of the accuracy verification of the elevation error analysis model of the laser height measurement foot point of the laser 1 provided by the present invention; Figure 7 A coordinate schematic diagram of an embodiment of a scatter diagram of the accuracy verification of the elevation error analysis model of the laser height measurement foot point of the laser 2 provided by the present invention; Figure 8 A schematic structural diagram of an embodiment of a device for analyzing elevation errors of satellite laser altimetry footpoint positioning provided by the present invention; Fig. 9 A schematic structural diagram of an embodiment of an electronic device provided by the present invention. DETAILED DESCRIPTION

[0022] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0023] like Figure 1As shown, a specific embodiment of the present invention discloses a method for analyzing elevation errors of satellite laser altimetry footpoint positioning, comprising: S101, acquiring sensor data of a satellite sensor and discrete full waveform data of a laser sent by a satellite laser altimeter, establishing a satellite laser ranging error model, and determining influencing error factors; the influencing error factors include laser ranging errors; S102, inputting the discrete full waveform data into a satellite laser ranging error model to obtain a laser ranging error value of the laser ranging error; S103, obtaining a satellite laser foot point positioning elevation comprehensive error value according to the sensor data and the laser ranging error value.

[0024] It should be understood that the analysis of the elevation error of satellite laser altimeter footpoint positioning must first focus on the strict geometric model of satellite laser altimeter footpoint positioning. The specific solution process of satellite laser altimeter footpoint positioning mainly involves five coordinate frames, such as Figure 2 , respectively, laser measurement coordinate system, satellite reference coordinate system, International Celestial Reference Frame (ICRF), International Terrestrial Reference Frame (ITRF) and geodetic ellipsoid coordinate system. The definitions of each coordinate system are as follows: (a) Laser measurement platform coordinate system: The laser emission reference point is , x The axis points to the direction of satellite flight. z The axis points toward the nadir. y The axis is perpendicular to the orbital plane and x , z The axes form a right-handed coordinate system; (b) Satellite reference coordinate system: The coordinate axis points in the same direction as the laser measurement coordinate system, and there is only an origin offset from the laser measurement coordinate system. The origin is ; (c) International Celestial Reference Frame (ICRF): recommended by the International Earth Rotation and Reference Systems Services (IERS). x The axis points to the J2000.0 dynamical equinox. ), z The axis points to the North celestial pole (NCP). y Axis and x , zThe axes form a right-handed coordinate system, which is an inertial reference system. It should be noted that the ICRF used by the GF-7 laser altimeter is the Geocentric Celestial Reference System (GCRS), so the origin is located at the center of mass of the Earth. (d) International Terrestrial Reference Frame (ITRF): An Earth-fixed coordinate system with its origin at the Earth’s center of mass. x The axis points to the intersection of the Greenwich meridian and the equator. z The axis points to the Conventional Terrestrial Pole (CTP), y Axis and x , z The axes form a right-handed coordinate system.

[0025] (e) Geodetic coordinate system: A coordinate system established with the reference ellipsoid as the reference surface. It is determined by the ellipsoid, ellipsoid positioning parameters, ellipsoid orientation parameters and geodetic starting data. The position of the ground point is expressed by geodetic longitude, geodetic latitude and elevation.

[0026] Figure 2 Schematic diagram of the strict positioning geometric model of the Gaofen-7 satellite laser altimetry: (a) The coordinate conversion of the satellite laser altimetry from the laser measurement coordinate system to the international earth reference frame, , They are the coordinate origins of the laser measurement coordinate system and the satellite reference coordinate system respectively. The two coordinate systems only have an origin offset. is the origin of the International Celestial Reference Frame (GEO) and the International Terrestrial Reference Frame, and is also the center of mass of the Earth; (b) is a schematic diagram of the conversion of the satellite laser altimeter foot point from the International Terrestrial Reference Frame to the Geodetic Ellipsoid Coordinate System. , and The longitude, latitude and elevation of the laser foot point. The final solution coordinates of the satellite laser altimeter foot point are usually located in the international earth reference frame or geodetic coordinate system. Among them, the coordinates of the laser foot point in the international earth reference coordinate system can be expressed as shown in formula (1): (1) In the formula, is the laser distance measurement value, , , Distribution as laser axis ( Figure 1 In ) with the x-axis, y-axis and z-axis of the laser measurement platform coordinate system; , and It is the origin offset of the laser measurement platform coordinate system relative to the satellite reference coordinate system, and the two coordinate systems have the same axial direction.

[0028] The satellite platform is equipped with a satellite orbit determination and attitude determination system, which can determine the orbital position and attitude information of the satellite at different times. The phase center of the GPS antenna does not coincide with the center of mass of the satellite platform (the origin of the satellite reference coordinate system). The offset of the phase center of the GPS antenna relative to the origin of the satellite reference coordinate system ,in addition, is the coordinate of the phase center of the GPS antenna in the international celestial reference coordinate system, The rotation matrix is ​​the conversion of the satellite reference coordinate system determined by the star sensor and gyroscope to the international celestial reference coordinate system; is a 3×3 matrix, which is the conversion matrix from the National Celestial Reference Frame ICRF to the International Terrestrial Reference Frame ITRF. Due to the influence of the earth's nutation, precession and polar motion, the parameters of the ITRF frame change with time. It is closely related to the time when the laser reaches the surface. The rotation matrix parameters can be calculated based on the precession and nutation model published by IERS, polar motion data, and UT1 time. The coordinates of the laser foot point can also be converted from ITRF to the geodetic ellipsoid coordinate system, and finally the longitude, latitude and elevation coordinates of the laser foot point in the geodetic coordinate system are solved. Among them, it is assumed that the lengths of the major and minor axes of the ellipsoid are a and b respectively, located at ITRF ( X , Y , Z ) and the geodetic ellipsoid coordinate system ( , , ) is shown in formula (2): (2) in, , .

[0029] In a specific embodiment of the present invention, the sensor data of each sensor can be obtained through the satellite sensor, for example, the satellite attitude data is measured by the on-board attitude sensor, and the orbital positioning sensor measures the orbital position of the satellite platform. After being transmitted to the satellite, the precise attitude and precise orbit data can be output after precise attitude and precise orbit determination processing, etc. The specific satellite sensor and the sensor data can be set according to the actual situation, and the embodiment of the present invention is not limited here. The laser emitted by the satellite laser altimeter undergoes a Fresnel diffraction, is incident on the surface of the earth, is reflected by the target, and then undergoes a Fresnel diffraction, and finally reaches the telescope field of view and is received. After the signal gain, photoelectric conversion and sampling processes, digital discrete full waveform data is obtained. Then, a satellite laser ranging error model can be established according to the results of data analysis, and the influencing error factors can be determined. The influencing error factors can include laser ranging errors, so that the discrete full waveform data can be input into the satellite laser ranging error model. The satellite laser ranging error model can output the laser ranging error value of the laser ranging error. Then, according to the detected satellite sensor data and laser ranging error value, the satellite laser foot point positioning elevation comprehensive error value can be calculated.

[0030] Compared with the prior art, the present embodiment provides the method of obtaining sensor data of a satellite sensor and discrete full waveform data of a laser sent by a satellite laser altimeter, establishing a satellite laser ranging error model, and determining influencing error factors; the influencing error factors include laser ranging error; the discrete full waveform data is input into the satellite laser ranging error model to obtain a laser ranging error value of the laser ranging error; according to the sensor data and the laser ranging error value, a satellite laser footprint positioning elevation comprehensive error value is obtained; the present invention can calculate the laser ranging error value through the satellite laser ranging error model, thereby obtaining the satellite laser footprint positioning elevation comprehensive error value through the laser ranging error value and data detected by other sensors, without the need to input terrain parameters in the laser footprint, thereby improving the availability of the model.

[0031] Furthermore, before carrying out the embodiments of the present invention, the experimenter can compare and analyze the data according to the actual situation to determine the influencing error factors. The specific analysis process can be divided into ① analysis of the influence of satellite laser ranging error on laser foot point positioning error; ② analysis of the influence of laser optical axis pointing error on laser foot point positioning error; ③ analysis of the influence of satellite attitude measurement error on laser foot point positioning error; ④ analysis of the influence of satellite positioning error on laser foot point positioning error.

[0032] ① Analysis of the influence of satellite laser ranging error on laser foot point positioning error In order to conduct a more comprehensive simulation analysis of the laser ranging error on the laser foot point positioning error, the embodiment of the present invention calculates the error at different satellite attitude angles ( Roll , Pitch, Yaw ) and different angles between the laser optical axis and the laser measurement platform coordinate system ( , , ) The influence of different laser ranging errors on the laser foot point positioning error. As shown in Table 1 and Table 2: Table 1. Foot point positioning (X-East, Y-North, Z-Height) errors caused by laser ranging errors under different satellite attitudes

[0033] Table 1 lists the simulation calculation results of the laser footpoint positioning error caused by some different laser ranging errors under different satellite attitudes. It can be seen that the footpoint positioning elevation error (absolute value) caused by the laser ranging error is equivalent to the laser ranging error, that is, there is a 1:1 relationship. Even when the satellite sway deviates from the reference level by about 7.2°, the footpoint positioning elevation error and the laser ranging error are only 8 mm apart. At this time, the footpoint position plane error caused by the laser ranging error is less than 13 cm, and the impact on the footpoint positioning plane accuracy is almost negligible.

[0034] Table 2. Simulation results of foot point positioning error caused by laser ranging error at different angles between the laser optical axis and the laser measurement platform coordinate system

[0035] It is easy to find from Table 2 that the laser foot point positioning error caused by the laser ranging error has nothing to do with the three-axis angle between the laser optical axis and the laser measurement platform coordinate system.

[0036] Based on Table 1 and Table 2, it can be considered that the laser ranging error is equivalent to the laser foot point positioning elevation error caused by it, and is independent of the different satellite platform attitude angles and the three-axis angles between the laser optical axis and the measurement platform coordinate system; the laser foot point positioning plane error caused by the laser ranging error can be ignored.

[0037] ②Analysis of the influence of the pointing error in the laser optical axis on the positioning error of the laser foot point The angle between the laser optical axis and the three axes of the laser measurement platform coordinate system (in formula (1) , , , inward pointing) is related to the internal optical path of the laser, and has nothing to do with the satellite platform attitude, orbital position, and laser ranging. The laser foot point positioning error caused by different measurement errors of the three-axis angle between the laser optical axis and the measurement platform coordinate system at different angles is simulated and analyzed. As shown in Table 3: Table 3, Laser Pointing ( ， ， ) Error in foot position (X-East, Y-North, Z-Height) caused by error

[0038] By analyzing Table 3, it can be found that the laser optical axis and the laser measurement platform coordinates x axis, y Axis and z The measurement error of the angle between the axes and the resulting laser foot positioning error are both linearly related; the laser optical axis and the laser measurement platform coordinate system x Axis and y The measurement error of the angle of the axis mainly affects the plane positioning accuracy of the laser foot point, and has little effect on the elevation accuracy of the foot point. When the angle measurement error reaches 5 arc seconds and the foot point plane error exceeds 12m, the resulting foot point positioning elevation error does not exceed 5cm; while the laser optical axis and the measurement platform coordinate system z The measurement error of the axis angle only affects the elevation accuracy of the foot point positioning, and the impact on the plane position of the foot point positioning can be ignored.

[0039] ③Analysis of the influence of satellite attitude measurement error on laser foot point positioning error The satellite platform attitude is measured by independent star sensors and gyroscopes, and has nothing to do with the orbital position, laser ranging, and the angle between the laser optical axis and the measurement platform coordinate system. The laser foot positioning error caused by the three-axis attitude angle measurement error of the satellite platform is simulated and calculated, as shown in Table 4: Table 4. Simulation results of laser foot positioning error caused by satellite attitude angle measurement error

[0040] By analyzing Table 4, it can be found that the satellite attitude angle measurement error and the laser height measurement foot point positioning error show a linear correlation; the attitude angle measurement error mainly affects the plane positioning accuracy of the laser foot point. The 1 arc second measurement error of the roll angle corresponds to a laser foot point plane positioning error of about 2.5m, and the 1 arc second measurement error of the pitch angle corresponds to a laser foot point plane positioning error of about 2.44m. The yaw angle measurement error affects the plane positioning of the laser foot point only in the X direction, among which, the 1 arc second measurement error corresponds to a plane error of about 1.53m. The attitude angle measurement error also affects the elevation accuracy of the laser foot point positioning, among which, the 3 arc second measurement error of the roll angle can lead to an elevation error of about 10.7cm.

[0041] ④ Analysis of the influence of satellite positioning error on laser foot point positioning error The satellite realizes orbital positioning by carrying an independent GPS device, which is unrelated to the laser ranging, the angle between the laser optical axis and the measurement platform coordinate system, and the satellite attitude measurement. The laser foot point positioning error caused by the orbital position measurement error is simulated and calculated, as shown in Table 5 below: Table 5. Simulation results of laser foot positioning error caused by satellite three-axis positioning error

[0042] It can also be found from Table 5 that the measurement error of the satellite orbit position (located in the ICRF framework) and the laser foot positioning error caused by it are linearly correlated, where the satellite orbit position x Direction and z The measurement error in direction has a great influence on the elevation accuracy of laser foot point positioning, and the satellite orbit position can be calculated. x direction, y direction, z A 10cm measurement error in direction can result in errors of approximately 6cm, 0.8cm, and 7.9cm in the elevation direction of the laser foot positioning.

[0043] In some embodiments of the present invention, step S101 includes: Based on the satellite laser altimetry echo theory, the discrete full waveform data is analyzed to obtain the laser ranging error factor that affects the laser ranging error. The satellite laser ranging error model is established by performing simulation calculation based on the laser ranging error factor.

[0044] In a specific embodiment of the present invention, according to the satellite laser altimetry echo theory, it is assumed that the surface contour within the laser footprint satisfies the state traversal, and the echo waveform shape is related to the distribution of the surface terrain undulation within the footprint. When the laser altimetry system is incident obliquely on the surface slope, Figure 3 As shown, Figure 3 This is a schematic diagram of the laser altimeter system obliquely incident on the surface slope. and are the terrain aspect angles of the terrain within the footprint parallel and perpendicular to the satellite flight direction, respectively; The point is the location of the satellite; is the laser pointing angle; is the height from the satellite to the earth’s surface; For the plane position The analytical function of terrain undulation is used. The geometric physical modeling of the relationship between the echo waveform and the target terrain characteristics is carried out. The factors that affect the broadening of the laser echo pulse width include the laser altimeter system itself, the surface slope (slope aspect) roughness, the beam curvature, the beam pointing angle and the divergence angle. At this time, the mean square pulse width of the echo waveform of the full waveform laser altimeter system can be expressed as shown in formula (3): (3) In the formula, , and are the laser echo pulse width, the laser emission pulse width and the detector pulse response pulse width respectively; is the laser pointing angle (the angle between the laser optical axis and the nadir direction); is the laser divergence angle; is the speed of light in a vacuum; is the satellite orbit altitude; and is the terrain aspect angle of the terrain in the footprint parallel and perpendicular to the satellite flight direction; is the root mean square roughness.

[0046] The variance expression of the time center of gravity of the echo signal is shown in formula (4): (4) In the formula, echo time center of gravity; is the mean square pulse width of the echo; is the photodetector noise factor, which is approximately 1; is the number of photons contained in the echo; is the number of background noise photons; is the detector dark current noise; is the detector thermal noise; Amplifies noise for the detector pre-circuit; is the detector integration time; is the sampling time resolution of the echo waveform; is the speckle signal-to-noise ratio, and is; is the mean square roughness of the terrain within the footprint; is the laser pointing angle; is the terrain slope within the footprint in the along-track direction; is the terrain slope within the footprint in the vertical direction; is the laser divergence angle; is the speed of light in vacuum, which is 299792458 m / s; is the height from the satellite to the earth’s surface; is the laser pointing uncertainty along the track; is the laser pointing uncertainty in the vertical track direction; is the detector receiving aperture area; is the laser wavelength.

[0047] The first term in formula (4) is the time center of gravity error caused by the emission pulse time center of gravity error and the detector sampling noise; the second term is the time center of gravity error caused by background noise, detector dark thermal noise, dark current noise and front circuit amplification noise; the third term is the time center of gravity error caused by terrain roughness; the fourth term is the time center of gravity error caused by beam curvature; the fifth term is the time center of gravity error caused by non-nadir direction measurement and terrain slope; the sixth term is the time center of gravity error caused by laser pointing jitter. For the full waveform satellite laser altimetry system, the ranging error caused by detector sampling noise and emission pulse is no more than 3cm and can be directly calculated; the ranging error caused by detector noise and background noise can be eliminated by waveform noise filtering; the ranging error caused by terrain factors, laser non-nadir direction measurement and pointing angle measurement errors can be derived from formulas (3) and (4) to obtain formula (5): (5) It can be seen that in order to calculate this distance measurement error, it is necessary to obtain the accurate slope information of the terrain within the footprint ( and ). However, from formula (3) and formula (5), it can be found that information such as the terrain aspect in the laser footprint will not only cause the echo pulse width to broaden, but will also cause laser ranging errors together with laser pointing angle jitter, laser non-nadir direction measurement, etc., that is, determine the laser ranging error factor. For this reason, the embodiment of the present invention considers establishing an empirical model of terrain feature parameters (slope aspect, roughness)-echo pulse width broadening-laser ranging error, that is, a satellite laser ranging error model, to accurately evaluate the laser ranging error value caused by laser pointing angle jitter, surface aspect in the footprint, and non-nadir direction measurement.

[0049] Formula (3) can express the echo pulse width broadening caused by terrain factors (slope aspect, roughness) as shown in formula (6): (6) In the formula, is the laser echo pulse width; is the laser emission pulse width; is the pulse width of the detector pulse response.

[0051] By simulating the laser ranging error caused by terrain factors, laser pointing jitter, laser non-nadir direction measurement, and echo pulse width broadening simulation calculation, the formula of the satellite laser ranging error model can be established as shown in formula (7): (7) In the formula, , , is the fitting parameter, and the fitting error evaluation index , .

[0052] Based on formulas (4), (5), (6) and (7), the timing variance of satellite laser altimetry caused by the centroid error of the transmitted pulse time, detector sampling noise, terrain slope (slope aspect), roughness, beam curvature, laser non-nadir direction measurement and laser pointing angle jitter is shown in formula (8): (8) In the formula, echo time center of gravity; is the laser echo pulse width; is the laser emission pulse width; is the pulse width of the detector pulse response; is the laser pointing angle; is the laser divergence angle; is the speed of light in a vacuum; is the height from the satellite to the earth’s surface; , , is the fitting parameter; is the photodetector noise factor; is the number of photons contained in the echo; is the sampling time resolution of the echo waveform; is the mean square pulse width of the echo; is the speckle signal-to-noise ratio.

[0054] The ranging error calculation is shown in formula (9): (9) In the formula, is the speed of light in a vacuum; is the satellite laser altimetry timing variance.

[0055] In some embodiments of the present invention, Figure 4 As shown, step S102 includes: S401, analyzing the discrete full waveform data to obtain the laser echo pulse width, the laser emission pulse width, and the detector pulse response pulse width; S402, calculating the laser echo pulse width, the laser emission pulse width and the detector pulse response pulse width according to the timing variance calculation formula of the satellite laser ranging error model to obtain the satellite laser altimetry timing variance; S403, calculating the satellite laser altitude and timing variance according to the ranging error calculation formula of the satellite laser ranging error model to obtain a laser ranging error value of the laser ranging error.

[0056] In a specific embodiment of the present invention, the three-axis angle between the laser optical axis and the laser measurement platform coordinate system in ①, ②, ③ and ④ above, the satellite attitude angle and the satellite orbital position are all measured by independent devices. For example, the satellite attitude data is measured by the on-board attitude sensor, and the orbital positioning sensor measures the orbital position of the satellite platform. After being transmitted to the satellite, they are respectively processed by precise attitude determination and precise orbit determination to output precise attitude and precise orbit data, etc. The measurement errors of these elements and the laser foot point positioning elevation error caused by the laser ranging error are independent of each other. Combined with the satellite laser ranging error model and the analysis results of steps ①, ②, ③ and ④, each measurement error is linearly correlated with the laser foot point positioning elevation error caused by it. The received discrete full waveform data can also be analyzed to obtain the laser echo pulse width, laser emission pulse width, and detector pulse response pulse width. The laser divergence angle and laser pointing angle can also be detected according to the laser emitting device. These can all be obtained through measurement. The discrete full waveform data can be input into formula (8) to calculate the satellite laser altimetry and timing variance. The satellite laser altimetry and timing variance can then be input into formula (9) for calculation. The satellite laser ranging error model can then output the laser ranging error value of the laser ranging error.

[0057] In some embodiments of the present invention, the influencing error factors also include the laser optical axis pointing error, the satellite attitude measurement error and the satellite positioning error; the sensor data includes the three-axis angle between the laser optical axis and the laser measurement platform coordinate system, the satellite attitude angle, the satellite orbit position and the ranging distance; step S103 includes: Obtaining a laser optical axis inner pointing error value of a laser optical axis inner pointing error, a satellite attitude measurement error value of a satellite attitude measurement error, and a satellite positioning error value of a satellite positioning error; The laser foot point elevation is obtained based on the three-axis angle, satellite attitude angle, satellite orbit position and ranging distance; According to the comprehensive model of satellite laser altimetry footpoint positioning elevation error, the laser ranging error value, the laser optical axis pointing error value, the satellite attitude measurement error value and the satellite positioning error value are calculated to obtain the comprehensive error value of satellite laser footpoint positioning elevation.

[0058] In a specific embodiment of the present invention, according to the analysis of ①, ②, ③ and ④ above, it can be determined that the influencing error factors also include the pointing error in the laser optical axis, the satellite attitude measurement error and the satellite positioning error, and the error values ​​of these errors can be obtained by other means, for example, the test personnel can obtain the error values ​​of these errors based on information or other data, and can be specifically set according to actual conditions. The present invention does not limit these error values. A satellite laser altimetry foot point positioning elevation error comprehensive model can also be set. The satellite laser altimetry foot point positioning elevation error comprehensive model can be used to process the three-axis angle, satellite attitude angle, satellite orbit position and ranging distance obtained by the satellite sensor to calculate the laser foot point elevation. For example, it is assumed that the laser foot point elevation calculation formula can be expressed as shown in formula (10): (10) Then, the laser ranging error value, the laser optical axis pointing error value, the satellite attitude measurement error value and the satellite positioning error value can be substituted into the satellite laser height measurement foot point positioning elevation error comprehensive model formula (11) to calculate the satellite laser foot point positioning elevation comprehensive error value. Formula (11) is as follows: (11) in: , ,

[0060] In the formula, It is the comprehensive error value of satellite laser foot point positioning elevation; is the laser foot point elevation; Satellite orbital position x, y, z Measurements in the axial direction; The satellite orbital position after precise orbit determination x, y, z Positioning information in the axis direction; is the satellite orbital position x, y, z Satellite positioning error value in the axis direction; is the measured value of the satellite attitude angle; It is the three-axis attitude angle of the satellite after precise attitude determination; is the coordinates of the laser optical axis and the laser measurement platform x, y, z The measured value of the angle in the axial direction; is the coordinates of the laser optical axis and the laser measurement platform x, y, z The laser optical axis pointing error value of the angle in the axial direction; is the laser ranging error value

[0061] The embodiment of the present invention first analyzes the factors affecting the laser ranging accuracy, and establishes an analytical empirical model of the laser ranging error caused by uncorrectable error factors such as laser non-nadir direction measurement, laser pointing jitter error, and surface target characteristics, wherein a satellite laser ranging error model is established by simulating and calculating the echo pulse width broadening and ranging error caused by terrain factors, thereby avoiding the input of terrain parameters in the ranging error analysis of the satellite laser altimetry system; then, based on the satellite laser ranging error model, the factors affecting the elevation error of the laser altimetry footpoint positioning are discussed and the error simulation calculation is performed, and it is analyzed whether the elevation errors of the footpoint positioning caused by different factors are related, and finally, a comprehensive error formula for the laser altimetry positioning elevation under the influence of multiple factors such as satellite laser ranging error, satellite laser optical axis pointing error, satellite attitude measurement error, and satellite orbit positioning error is derived, so as to realize the accurate analysis of the elevation accuracy of the satellite laser altimetry footpoint positioning.

[0062] Further, such as Figure 5 As shown in the figure, the experimental area is taken as an example. The area contains a variety of landforms, such as plains, hills, mountains and canyons. The experimental data includes the real laser altimetry data of GF-7 and high-precision airborne point cloud data, such as Figure 5 The blue dots shown in the figure represent laser footprints; the average spatial resolution of the airborne laser point cloud is 1m, and the plane and elevation accuracies are 0.5m and 0.2m respectively. Special note on the timeliness of the verification data (airborne point cloud): The environmental facilities related to residents' lives in the experimental area, such as urban buildings, roads, fields, and houses, are updated and renovated slowly. It can be considered that the time difference between the airborne point cloud and the transit laser altimetry data in such areas has little effect on the evaluation of the elevation accuracy of the laser altimetry footpoint positioning; while the time difference between the airborne point cloud and the transit laser altimetry data in the forest area will greatly affect the evaluation of the altimetry accuracy. Therefore, the laser altimetry points in the forest area will not be involved in the evaluation of the accuracy of the laser altimetry point elevation error analysis.

[0063] Based on the satellite laser altimetry data collected when GF-7 passed through the experimental area in six periods, in order to accurately verify the accuracy of the satellite laser altimetry error analysis model established in the scheme of the present invention, the embodiment of the present invention only used laser altimetry data containing only one component in the laser altimetry echo waveform decomposition. Among them, the number of laser points of laser 1 and laser 2 were 87 and 85 respectively. After eliminating the laser points falling in the forest area, 80 and 76 remained respectively. In the experiment, the laser altimetry error analysis model was first used to calculate the elevation error of the laser altimetry point, and then the high-precision airborne point cloud was used to verify the elevation error of the laser altimetry point. The latter can be considered as the true error evaluation of the laser altimetry point. Finally, the error evaluation results of the two are analyzed and compared. The specific accuracy verification results are as follows Figure 6 and Figure 7As shown, the horizontal axis is the laser foot point positioning elevation error value obtained by analyzing the satellite laser altimetry elevation error analysis model established using an embodiment of the present invention, and the vertical axis is the error evaluation value of the laser foot point positioning elevation using a high-precision airborne laser point cloud. Figure 6 and Figure 7 This is a scatter plot of the error model analysis results of the laser altimeter foot point elevation of the GF-7 satellite-borne laser altimeter laser 1 and laser 2 and the error verification results of the airborne point cloud. Figure 6 It is a scatter plot of the accuracy verification of the elevation error analysis model of the laser height measurement foot point of laser 1; Figure 7 This is a scatter plot of the accuracy verification of the elevation error analysis model for the laser height measurement foot point of Laser 2.

[0064] It can be found that the error analysis results of the satellite-borne laser altimetry error analysis model are well consistent with the error verification results of the airborne point cloud. Figure 6 In the test, the maximum elevation error of the laser altimetry points collected by the GF-7 laser 1 was 2.92m, as verified by the airborne point cloud. At this time, the elevation error of the laser foot point positioning obtained by the satellite-borne laser altimetry error analysis model was 2.87m, with a difference of only 0.05m. Figure 7 In the figure, the maximum elevation error of the laser altimetry points collected by laser 2 is 2.56m after verification by the airborne point cloud. At this time, the elevation error of the laser foot point positioning obtained by the satellite-borne laser altimetry error analysis model is 2.27m, which is only 0.29m different. The accuracy evaluation indicators mean absolute error (MAE) and root mean square error (RMSE) are used to evaluate the accuracy of the satellite-borne laser altimetry error model established in this paper, as shown in Table 6: Table 6. Accuracy evaluation of the elevation error analysis model for the GF-7 satellite laser altimetry footpoint positioning

[0065] Experiments show that the satellite laser altimetry error analysis model established in the embodiment of the present invention can better perform quantitative error analysis on the full-waveform satellite laser altimetry footpoint positioning elevation. The accuracy evaluation index is used to evaluate the elevation analysis accuracy of the satellite laser altimetry error analysis model established in the embodiment of the present invention. The error analysis model has an error analysis accuracy of 0.2538m (MAE) and 0.2325m (RMSE) for the footpoint coordinate elevation of GF-7 laser 1, an error analysis accuracy of 0.2538m (MAE) and 0.2325m (RMSE) for the footpoint coordinate elevation of GF-7 laser 2, and an overall error analysis accuracy of 0.2876m (MAE) and 0.3353m (RMSE) for the footpoint coordinate elevation of GF-7 laser.

[0066] In order to better implement the satellite laser altimetry foot point positioning elevation error analysis method in the embodiment of the present invention, based on the satellite laser altimetry foot point positioning elevation error analysis method, the embodiment of the present invention also provides a satellite laser altimetry foot point positioning elevation error analysis device, such as Figure 8 As shown, the satellite laser altimetry foot point positioning elevation error analysis device 800 includes: The data acquisition module 801 is used to acquire sensor data of the satellite sensor and discrete full waveform data of the laser sent by the satellite laser altimeter, establish a satellite laser ranging error model, and determine the influencing error factors; the influencing error factors include laser ranging errors; The error value calculation module 802 is used to input the discrete full waveform data into the satellite laser ranging error model to obtain the laser ranging error value of the laser ranging error; The elevation error calculation module 803 is used to obtain the satellite laser foot point positioning elevation comprehensive error value according to the sensor data and the laser ranging error value.

[0067] The satellite laser altimetry footpoint positioning elevation error analysis device 800 provided in the above embodiment can implement the technical solution described in the above satellite laser altimetry footpoint positioning elevation error analysis method embodiment. The specific implementation principles of the above modules or units can refer to the corresponding contents in the above satellite laser altimetry footpoint positioning elevation error analysis method embodiment, which will not be repeated here.

[0068] like Fig. 9 As shown, the present invention also provides an electronic device 900. The electronic device 900 includes a processor 901, a memory 902 and a display 903. Fig. 9 Only some components of the electronic device 900 are shown, but it should be understood that it is not required to implement all of the components shown, and more or fewer components may be implemented instead.

[0069] In some embodiments, the memory 902 may be an internal storage unit of the electronic device 900, such as a hard disk or memory of the electronic device 900. In other embodiments, the memory 902 may also be an external storage device of the electronic device 900, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc., equipped on the electronic device 900.

[0070] Furthermore, the memory 902 may include both an internal storage unit of the electronic device 900 and an external storage device. The memory 902 is used to store application software installed in the electronic device 900 and various data.

[0071] In some embodiments, the processor 901 may be a central processing unit (CPU), a microprocessor or other data processing chip, used to run program codes or process data stored in the memory 902, such as the satellite laser altimetry footpoint positioning elevation error analysis method of the present invention.

[0072] In some embodiments, the display 903 may be an LED display, a liquid crystal display, a touch-sensitive liquid crystal display, an OLED (Organic Light-Emitting Diode) touch device, etc. The display 903 is used to display information of the electronic device 900 and to display a visual user interface. The components 901-903 of the electronic device 900 communicate with each other through a system bus.

[0073] In some embodiments of the present invention, when the processor 901 executes the satellite laser altimetry footpoint positioning elevation error analysis program in the memory 902, the following steps may be implemented: Obtain sensor data from satellite sensors and discrete full waveform data of lasers sent by satellite laser altimeters, establish a satellite laser ranging error model, and determine factors affecting the error; factors affecting the error include laser ranging errors; Inputting the discrete full waveform data into the satellite laser ranging error model to obtain the laser ranging error value of the laser ranging error; According to the sensor data and the laser ranging error value, the comprehensive error value of the satellite laser foot point positioning elevation is obtained.

[0074] It should be understood that: when the processor 901 executes the satellite laser altimetry footpoint positioning elevation error analysis program in the memory 902, in addition to the above functions, other functions can also be implemented. For details, please refer to the description of the corresponding method embodiment above.

[0075] Furthermore, the embodiment of the present invention does not specifically limit the type of the electronic device 900 mentioned, and the electronic device 900 may be a portable electronic device such as a mobile phone, a tablet computer, a personal digital assistant (PDA), a wearable device, a laptop computer, etc. Exemplary embodiments of portable electronic devices include but are not limited to portable electronic devices equipped with IOS, Android, Microsoft or other operating systems. The above-mentioned portable electronic devices may also be other portable electronic devices, such as a laptop computer with a touch-sensitive surface (e.g., a touch panel). It should also be understood that in some other embodiments of the present invention, the electronic device 900 may not be a portable electronic device, but a desktop computer with a touch-sensitive surface (e.g., a touch panel).

[0076] Accordingly, an embodiment of the present application also provides a computer-readable storage medium, which is used to store computer-readable programs or instructions. When the program or instructions are executed by a processor, the steps or functions of the satellite laser altimetry footpoint positioning elevation error analysis method provided in the above-mentioned method embodiments can be implemented.

[0077] Those skilled in the art will appreciate that all or part of the processes of the above-mentioned embodiments can be implemented by instructing related hardware (such as a processor, a controller, etc.) through a computer program, and the computer program can be stored in a computer-readable storage medium, wherein the computer-readable storage medium is a disk, an optical disk, a read-only storage memory, or a random access memory, etc.

[0078] The above is a detailed introduction to the satellite laser altimetry footpoint positioning elevation error analysis method, device, equipment and medium provided by the present invention. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for technical personnel in this field, according to the idea of ​​the present invention, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A method for analyzing the elevation error of a satellite laser altimetry footpoint, characterized in that: include: Acquire sensor data of a satellite sensor and discrete full waveform data of a laser sent by a satellite laser altimeter, establish a satellite laser ranging error model, and determine influencing error factors; the influencing error factors include laser ranging errors; Inputting the discrete full waveform data into the satellite laser ranging error model to obtain a laser ranging error value of the laser ranging error; According to the sensor data and the laser ranging error value, a satellite laser foot point positioning elevation comprehensive error value is obtained.

2. The method for analyzing the elevation error of a satellite laser altimetry footpoint according to claim 1, characterized in that: The satellite laser ranging error model is established, comprising: The discrete full waveform data is analyzed based on satellite laser altimetry echo theory to obtain a laser ranging error factor that affects the laser ranging error; A simulation calculation is performed based on the laser ranging error factor to establish a satellite laser ranging error model.

3. The method for analyzing elevation error of satellite laser altimetry footpoint positioning according to claim 1, characterized in that: The step of inputting the discrete full waveform data into the satellite laser ranging error model to obtain the laser ranging error value of the laser ranging error comprises: Analyzing the discrete full waveform data to obtain the laser echo pulse width, the laser emission pulse width and the detector pulse response pulse width; The laser echo pulse width, the laser emission pulse width and the detector pulse response pulse width are calculated according to the timing variance calculation formula of the satellite laser ranging error model to obtain the satellite laser altimetry timing variance; The satellite laser ranging error variance is calculated according to the ranging error calculation formula of the satellite laser ranging error model to obtain the laser ranging error value of the laser ranging error.

4. The method for analyzing elevation error of satellite laser altimetry footpoint positioning according to claim 1, characterized in that: The influencing error factors also include the laser optical axis pointing error, satellite attitude measurement error and satellite positioning error; the sensor data includes the three-axis angle between the laser optical axis and the laser measurement platform coordinate system, the satellite attitude angle, the satellite orbit position and the ranging distance; the satellite laser foot point positioning elevation comprehensive error value is obtained according to the sensor data and the laser ranging error value, including: Acquire a laser optical axis inward pointing error value of the laser optical axis inward pointing error, a satellite attitude measurement error value of the satellite attitude measurement error, and a satellite positioning error value of the satellite positioning error; Obtaining the laser foot point elevation according to the three-axis angle, the satellite attitude angle, the satellite orbit position and the ranging distance; According to the satellite laser altimetry foot point positioning elevation error comprehensive model, the laser ranging error value, the laser optical axis internal pointing error value, the satellite attitude measurement error value and the satellite positioning error value are calculated to obtain the satellite laser foot point positioning elevation comprehensive error value.

5. The method for analyzing elevation error of satellite laser altimetry footpoint positioning according to claim 3 is characterized in that: The timing variance calculation formula is: In the formula, echo time center of gravity; is the laser echo pulse width; is the laser emission pulse width; is the pulse width of the detector pulse response; is the laser pointing angle; is the laser divergence angle; is the speed of light in a vacuum; is the height from the satellite to the earth’s surface; , , is the fitting parameter; is the photodetector noise factor; is the number of photons contained in the echo; is the sampling time resolution of the echo waveform; is the mean square pulse width of the echo; is the speckle signal-to-noise ratio.

6. The method for analyzing elevation error of satellite laser altimetry footpoint positioning according to claim 3 is characterized in that: The ranging error calculation formula is: In the formula, is the speed of light in a vacuum; is the satellite laser altimetry timing variance.

7. The method for analyzing elevation error of satellite laser altimetry footpoint positioning according to claim 4, characterized in that: The comprehensive model of the elevation error of the satellite laser altimetry footpoint positioning is: ， ， ， In the formula, It is the comprehensive error value of satellite laser foot point positioning elevation; is the laser foot point elevation; Satellite orbital position x, y, z Measurements in the axial direction; The satellite orbital position after precise orbit determination x, y, z Positioning information in the axis direction; is the satellite orbital position x, y, z Satellite positioning error value in the axis direction; is the measured value of the satellite attitude angle; It is the three-axis attitude angle of the satellite after precise attitude determination; is the coordinates of the laser optical axis and the laser measurement platform x, y, z The measured value of the angle in the axial direction; is the coordinates of the laser optical axis and the laser measurement platform x, y, z The laser optical axis pointing error value of the angle in the axial direction; is the laser ranging error value.

8. A satellite laser height measurement foot point positioning elevation error analysis device, characterized in that: include: A data acquisition module is used to acquire sensor data of a satellite sensor and discrete full waveform data of a laser sent by a satellite laser altimeter, establish a satellite laser ranging error model, and determine influencing error factors; the influencing error factors include laser ranging errors; An error value calculation module, used for inputting the discrete full waveform data into the satellite laser ranging error model to obtain a laser ranging error value of the laser ranging error; The elevation error calculation module is used to obtain the comprehensive error value of the satellite laser foot point positioning elevation according to the sensor data and the laser ranging error value.

9. An electronic device, characterized in that: include: A processor, a memory, and a computer program stored in the memory and capable of running on the processor, wherein when the computer program is executed by the processor, the steps of the satellite laser altimetry footpoint positioning elevation error analysis method as described in any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the satellite laser altimetry footpoint positioning elevation error analysis method as described in any one of claims 1-7 are implemented.

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