Satellite laser altimeter footpoint positioning elevation error analysis method, device and medium

Abstract

This invention relates to a method, apparatus, and medium for analyzing elevation errors in satellite laser altimeter foothold positioning, belonging to the field of satellite surveying technology. The method includes acquiring sensor data from satellite sensors and discrete full-waveform data of laser light transmitted by a satellite laser altimeter; establishing a satellite laser ranging error model and determining influencing error factors, including laser ranging error; inputting the discrete full-waveform data into the satellite laser ranging error model to obtain the laser ranging error value; and obtaining a comprehensive elevation error value for satellite laser foothold positioning based on the sensor data and the laser ranging error value. This invention can calculate the laser ranging error value through the satellite laser ranging error model, thereby obtaining the comprehensive elevation error value for satellite laser foothold positioning from the laser ranging error value and data detected by other sensors, without requiring input of terrain parameters within the laser footprint, thus improving the usability of the model.

Description

Technical Field

[0001] This invention relates to the field of satellite detection technology, and in particular to a method, apparatus, equipment, and medium for analyzing elevation errors in satellite laser altimetry footpoint positioning. Background Technology

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

[0003] Existing technologies have used ICESat / GLAS laser altimetry data and high-precision airborne laser point clouds to verify the accuracy of established laser altimetry error analysis models. However, they have not calculated or verified the model accuracy for laser altimetry errors under significant terrain slopes. Furthermore, when spaceborne laser altimetry systems are actually operating, laser pointing errors and terrain slope factors will significantly affect laser ranging accuracy. Analyzing spaceborne laser altimetry errors based on all existing model methods requires terrain parameters within the laser footprint as known input parameters. However, for spaceborne laser altimetry points distributed globally, high-precision terrain parameters within their footprints are currently difficult to obtain, which greatly reduces the usability of existing model methods.

[0004] Therefore, there is an urgent need to propose a method, device, equipment, and medium for analyzing the elevation error of satellite laser altimetry footpoint positioning. This would solve the technical problem in existing technologies where models require terrain parameters within the laser footprint as known parameters for input, but high-precision terrain parameters within the footprint are currently difficult to obtain, leading to reduced model usability. Summary of the Invention

[0005] In view of this, it is necessary to provide a method, device, equipment and medium for analyzing the elevation error of satellite laser altimetry footpoint positioning, in order to solve the technical problem that the existing model requires the terrain parameters within the laser footprint as known parameters as input, but the high-precision terrain parameters within the footprint are currently difficult to obtain, which leads to a reduction in the usability of the model.

[0006] To address the aforementioned problems, this invention provides a method for analyzing elevation errors in satellite laser altimetry footpoint positioning, comprising:

[0007] Acquire sensor data from satellite sensors and discrete full waveform data of laser light transmitted by a satellite laser altimeter, establish a satellite laser ranging error model, and determine the error factors affecting the range; the error factors include laser ranging error.

[0008] The discrete full waveform data is input into the satellite laser ranging error model to obtain the laser ranging error value.

[0009] Based on the sensor data and the laser ranging error value, the comprehensive error value of satellite laser footpoint positioning elevation is obtained.

[0010] In one possible implementation, establishing the satellite laser ranging error model includes:

[0011] Based on the satellite laser altimeter echo theory, the discrete full waveform data is analyzed to obtain the laser ranging error factor that affects the laser ranging error.

[0012] Based on the laser ranging error factor, a satellite laser ranging error model is established through simulation calculation.

[0013] In one possible implementation, the step of inputting the discrete full-waveform data into the satellite laser ranging error model to obtain the laser ranging error value includes:

[0014] The discrete full waveform data is analyzed to obtain the laser echo pulse width, laser emission pulse width, and detector pulse response pulse width.

[0015] The timing variance of satellite laser altimetry is calculated by using the timing variance calculation formula of the satellite laser ranging error model to calculate the laser echo pulse width, the laser emission pulse width, and the detector pulse response pulse width, thereby obtaining the timing variance of satellite laser altimetry.

[0016] The variance of the satellite laser altimetry is calculated based on the ranging error calculation formula of the satellite laser ranging error model to obtain the laser ranging error value.

[0017] In one possible implementation, the influencing error factors further include laser optical axis pointing error, satellite attitude measurement error, and satellite positioning error; the sensor data includes the angles between the laser optical axis and the three axes of the laser measurement platform coordinate system, the satellite attitude angle, the satellite orbital position, and the ranging distance; the step of obtaining the comprehensive error value of satellite laser footpoint positioning elevation based on the sensor data and the laser ranging error value includes:

[0018] The laser optical axis pointing error value, the satellite attitude measurement error value, and the satellite positioning error value are obtained.

[0019] The laser foot point elevation is obtained based on the included angle of the three axes, the satellite attitude angle, the satellite orbital position, and the ranging distance;

[0020] The comprehensive error value of satellite laser footpoint positioning elevation is obtained by calculating the laser ranging error value, the laser optical axis pointing error value, the satellite attitude measurement error value, and the satellite positioning error value based on the comprehensive model of satellite laser footpoint positioning elevation error.

[0021] In one possible implementation, the formula for calculating the time-measurement variance is:

[0022]

[0023] In the formula, Echo time center of gravity; This refers to the laser echo pulse width; This refers to the laser emission pulse width; The pulse width of the detector's impulse response; This refers to the laser pointing angle; This refers to the laser divergence angle; The speed at which light travels in a vacuum; The altitude of the satellite above the Earth's surface; , , These are the fitting parameters; The noise factor of the photodetector; The number of photons contained in the echo; The sampling time resolution of the echo waveform; The mean square pulse width of the echo; The signal-to-noise ratio is for speckle patterns.

[0024] In one possible implementation, the ranging error calculation formula is:

[0025]

[0026] In the formula, The speed at which light travels in a vacuum; Variance of satellite laser altimetry timing.

[0027] In one possible implementation, the comprehensive model for the elevation error of the satellite laser altimeter footpoint positioning is as follows:

[0028]

[0029] , ,

[0030]

[0031] In the formula, The comprehensive error value for satellite laser footprint positioning elevation; Elevation of the laser footpoint; Satellite orbital position x, y, z Measurements along the axial direction; For the satellite's orbital position after precise orbit determination x, y, z Positioning information along the axis; For satellite orbital position x, y, z Satellite positioning error value along the axis; This refers to the measured value of the satellite's attitude angle; The three-axis attitude angles of the satellite after precise attitude determination; The coordinates of the laser optical axis and the laser measurement platform x, y, z The measured value of the included angle along the axial direction; The coordinates of the laser optical axis and the laser measurement platform x, y, z The laser optical axis pointing error value at the included angle in the axial direction; This represents the laser ranging error value.

[0032] On the other hand, the present invention also provides a satellite laser altimeter footpoint positioning elevation error analysis device, comprising:

[0033] The data acquisition module is used to acquire sensor data from satellite sensors and discrete full waveform data of laser light transmitted by satellite laser altimeters, establish a satellite laser ranging error model, and determine the error factors affecting the range; the error factors affecting the range include laser ranging error.

[0034] The error value calculation module is used to input the discrete full waveform data into the satellite laser ranging error model to obtain the laser ranging error value.

[0035] The elevation error calculation module is used to obtain the comprehensive elevation error value of satellite laser footpoint positioning based on the sensor data and the laser ranging error value.

[0036] On the other hand, embodiments of the present invention disclose an electronic device, including: a processor, a memory, and a computer program stored in the memory and capable of running on the processor. When the computer program is executed by the processor, it implements the various steps of the above-described embodiments of the satellite laser altimetry footpoint positioning elevation error analysis method.

[0037] On the other hand, embodiments of the present invention disclose a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the various steps of the above-described embodiments of the satellite laser altimetry footpoint positioning elevation error analysis method.

[0038] The beneficial effects of this invention are as follows: It acquires sensor data from satellite sensors and discrete full-waveform data of laser light transmitted by a satellite laser altimeter, establishes a satellite laser ranging error model, and determines the influencing error factors, including laser ranging error. The discrete full-waveform data is input into the satellite laser ranging error model to obtain the laser ranging error value. Based on the sensor data and the laser ranging error value, the comprehensive error value for satellite laser footprint positioning elevation is obtained. This invention can calculate the laser ranging error value through the satellite laser ranging error model, thereby obtaining the comprehensive error value for satellite laser footprint positioning elevation through the laser ranging error value and data detected by other sensors. It eliminates the need to input terrain parameters within the laser footprint, improving the usability of the model. Attached Figure Description

[0039] Figure 1 This is a schematic flowchart of an embodiment of the satellite laser altimetry footpoint positioning elevation error analysis method provided by the present invention;

[0040] Figure 2 A schematic diagram of an embodiment of the five coordinate frames provided by the present invention;

[0041] Figure 3 A schematic diagram of an embodiment of the laser altimetry system provided by the present invention, obliquely incident on a sloped surface;

[0042] Figure 4 For the present invention Figure 1 A schematic diagram of an embodiment of step S102;

[0043] Figure 5 A schematic diagram of an embodiment of experimental data collected in a certain region provided by the present invention;

[0044] Figure 6 A coordinate schematic diagram of an embodiment of the scatter plot for verifying the accuracy of the elevation error analysis model of the laser altimeter foot point of the laser 1 provided by the present invention;

[0045] Figure 7 A coordinate schematic diagram of an embodiment of the scatter plot for verifying the accuracy of the elevation error analysis model of the laser altimeter foot point of the laser 2 provided by the present invention;

[0046] Figure 8 This is a schematic diagram of an embodiment of the satellite laser altimeter footpoint positioning elevation error analysis device provided by the present invention;

[0047] Figure 9 A schematic diagram of an embodiment of the electronic device provided by the present invention. Detailed Implementation

[0048] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form 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 intended to limit the scope of the present invention.

[0049] like Figure 1 As shown, a specific embodiment of the present invention discloses a method for analyzing elevation errors in satellite laser altimetry footpoint positioning, comprising:

[0050] S101. Acquire sensor data from satellite sensors and discrete full waveform data of laser light transmitted by satellite laser altimeters, establish a satellite laser ranging error model, and determine the factors affecting the error; the factors affecting the error include laser ranging error.

[0051] S102. Input the discrete full waveform data into the satellite laser ranging error model to obtain the laser ranging error value;

[0052] S103. Based on the sensor data and the laser ranging error value, obtain the comprehensive error value of the satellite laser footpoint positioning elevation.

[0053] It should be understood that the elevation error analysis of satellite laser altimetry footpoint positioning should first focus on the rigorous geometric model of satellite laser altimetry footpoint positioning. The specific calculation process of satellite laser altimetry footpoint positioning mainly involves five coordinate frames, such as... Figure 2 These are the laser measurement coordinate system, the satellite reference coordinate system, the International Celestial Reference Frame (ICRF), the International Earth Reference Frame (ITRF), and the geodetic ellipsoidal coordinate system. The definitions of each coordinate system are as follows:

[0054] (a) Coordinate system of laser measurement platform: The laser emission reference point is , x The axis points in the direction of satellite flight. z The axis points towards the nadir. y The axis is perpendicular to the track plane, and x , z The axes form a right-handed coordinate system;

[0055] (b) Satellite reference coordinate system: The coordinate axes point in the same direction as the laser measurement coordinate system, with the only difference being the origin offset. The origin is... ;

[0056] (c) International Celestial Reference Frame (ICRF): Recommended by the International Earth Rotation and Reference Systems Service (IERS). x The axis points to the J2000.0 kinetic vernal equinox. ), z The axis points in the direction of the North Celestial Pole (NCP). y shaft and x , z The axes form a right-handed coordinate system, which is an inertial reference system. It should be noted that the ICRF used by the Gaofen-7 laser altimeter is the Geocentric Celestial Reference System (GCRS), so the origin is located at the Earth's center of mass.

[0057] (d) International Terrestrial Reference Frame (ITRF): A geofixed 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 shaft and x , z The axes form a right-handed coordinate system.

[0058] (e) Geodetic coordinate system: A coordinate system established with a reference ellipsoid as the reference surface. It is determined by the ellipsoid, ellipsoid positioning parameters, ellipsoid orientation parameters and geodetic datum data. The position of a point on the ground is expressed by geodetic longitude, geodetic latitude and elevation.

[0059] Figure 2 A schematic diagram of the rigorous positioning geometric model of the Gaofen-7 satellite laser altimeter: (a) Coordinate transformation from the laser measurement coordinate system to the International Geodetic Reference Frame (IGR). , These are the origins of the laser measurement coordinate system and the satellite reference coordinate system, respectively. The only difference between the two coordinate systems is the offset of the origin. (a) is the origin of the International Celestial Reference Frame (Geocentric Celestial Reference System) and the International Earth Reference Frame, and also the Earth's center of mass; (b) is a schematic diagram showing the transformation of the satellite laser altimeter's reference point from the International Earth Reference Frame to the geodetic ellipsoidal coordinate system. , and The final calculated coordinates of the laser footpoints (longitude, latitude, and elevation) from satellite laser altimetry are typically located in the International Geodetic Reference Frame (IGFR) or a geodetic coordinate system. The coordinates of the laser footpoints in the IGFR can be expressed as shown in formula (1):

[0060] (1)

[0062] In the formula, This is the laser ranging value. , , Distributed along the laser axis ( Figure 1 In The angle between the coordinate system and the x-axis, y-axis, and z-axis of the laser measurement platform. , and The coordinate system of the laser measurement platform is offset from the origin of the satellite reference coordinate system, and the axes of the two coordinate systems are the same.

[0063] The satellite platform carries a satellite orbit determination and attitude determination system, which can determine the satellite's orbital position and attitude information at different times. The phase center of the GPS antenna does not coincide with the satellite platform's center of mass (the origin of the satellite's reference coordinate system). The offset of the GPS antenna phase center relative to the origin of the satellite's reference coordinate system... ,in addition, The coordinates of the GPS antenna phase center in the International Celestial Reference Coordinate System are given. The rotation matrix is ​​used to transform the satellite reference coordinate system determined by the star sensor and gyroscope to the International Celestial Reference Coordinate System; rotation matrix This is a 3×3 matrix, representing the transformation matrix from the National Celestial Reference Frame (ICRF) to the International Earth Reference Frame (ITRF). Due to the influence of Earth's nutation, precession, and polar motion, the ITRF frame parameters change continuously over time. Closely related to the time of laser arrival at the Earth's surface, the rotation matrix parameters can be calculated based on the precession nutation model published by IERS, polar motion data, and UT1 time. The laser footprint coordinates can also be transformed from the ITRF to the geodetic ellipsoidal coordinate system, ultimately calculating the longitude, latitude, and elevation coordinates of the laser footprint in the geodetic coordinate system. Here, it is assumed that the lengths of the semi-major and semi-minor axes of the ellipsoid are a and b, respectively, and it is located within the ITRF (…). X , Y , Z ) and the geodetic ellipsoid coordinate system ( , , The coordinate relationship of the laser point under the condition is shown in formula (2):

[0064] (2)

[0065] in, , .

[0066] In a specific embodiment of the present invention, sensor data from each sensor can be acquired through satellite sensors. For example, satellite attitude data is measured by an onboard attitude sensor, and orbital positioning data is measured by an orbital positioning sensor. After being transmitted down to the ground, precise attitude and orbital data can be output through precise attitude and orbital determination processing. The specific satellite sensors and sensor data acquisition methods can be set according to actual conditions, and the embodiments of the present invention do not impose any limitations on this. The satellite laser altimeter emits a laser that undergoes Fresnel diffraction once, is incident on the Earth's surface, is reflected by the target, undergoes another Fresnel diffraction, and finally reaches the telescope's field of view and is received. After signal gain, photoelectric conversion, and sampling, digitized discrete full-waveform data is obtained. Then, a satellite laser ranging error model can be established based on the data analysis results, and the influencing error factors can be determined. The influencing error factors can include laser ranging error. Thus, the discrete full-waveform data can be input into the satellite laser ranging error model, which can output the laser ranging error value. Then, based on the detected satellite sensor data and the laser ranging error value, the comprehensive error value of the satellite laser footpoint positioning elevation can be calculated.

[0067] Compared with existing technologies, this embodiment provides a method for acquiring sensor data from satellite sensors and discrete full-waveform data of laser light transmitted by a satellite laser altimeter, establishing a satellite laser ranging error model, and determining influencing error factors, including laser ranging error. The discrete full-waveform data is input into the satellite laser ranging error model to obtain the laser ranging error value. Based on the sensor data and the laser ranging error value, a comprehensive error value for satellite laser footprint positioning elevation is obtained. This invention can calculate the laser ranging error value using the satellite laser ranging error model, thereby obtaining the comprehensive error value for satellite laser footprint positioning elevation from the laser ranging error value and data detected by other sensors. It eliminates the need to input terrain parameters within the laser footprint, improving the model's usability.

[0068] Furthermore, before conducting the embodiments of the present invention, the test personnel can compare and analyze the data according to the actual situation to determine the factors affecting the error. The specific analysis process can be divided into: ① Analysis of the influence of satellite laser ranging error on laser footpoint positioning error; ② Analysis of the influence of laser optical axis pointing error on laser footpoint positioning error; ③ Analysis of the influence of satellite attitude measurement error on laser footpoint positioning error; ④ Analysis of the influence of satellite positioning error on laser footpoint positioning error.

[0069] ① Analysis of the impact of satellite laser ranging error on laser footpoint positioning error

[0070] To conduct a more thorough simulation analysis of the impact of laser ranging error on laser footpoint positioning error, the embodiments of this invention calculate the impact of laser ranging error on laser footpoint positioning error at different satellite attitude angles ( Roll , Pitch, Yaw ) and the different angles between the laser optical axis and the coordinate system of the laser measurement platform ( , , The influence of different laser ranging errors on the laser footpoint positioning error is shown in Tables 1 and 2.

[0071] Table 1. Footpoint positioning errors (X-East, Y-North, Z-Height) caused by laser ranging errors under different satellite attitudes

[0072]

[0073] Table 1 lists the simulation results of laser footpoint positioning errors caused by 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 tilts away 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 its impact on the footpoint positioning plane accuracy is almost negligible.

[0074] Table 2. Simulation results of footpoint positioning errors caused by laser ranging errors under different angles between the laser optical axis and the coordinate system of the laser measurement platform.

[0075]

[0076] It is easy to see from Table 2 that the laser footpoint positioning error caused by the laser ranging error is unrelated to the angle between the laser optical axis and the three axes of the laser measurement platform coordinate system.

[0077] Based on Tables 1 and 2, it can be considered that the laser ranging error is equivalent to the elevation error of the laser footpoint positioning caused by it, and is independent of different satellite platform attitude angles and the three-axis angles between the laser optical axis and the measurement platform coordinate system; the plane error of the laser footpoint positioning caused by the laser ranging error can be ignored.

[0078] ② Analysis of the influence of laser optical axis pointing error on laser footpoint positioning error

[0079] The angle between the laser optical axis and the three axes of the laser measurement platform coordinate system (in formula (1)) , , The laser's internal optical path (inward pointing) is related to the satellite platform's attitude, orbital position, and laser ranging measurement. A simulation analysis is performed on the laser footpoint positioning error caused by different measurement errors at different angles between the laser optical axis and the three axes of the measurement platform coordinate system. (See Table 3.)

[0080] Table 3. Laser pointing ( ， ， Foot point positioning errors (X-East, Y-North, Z-Height) caused by errors

[0081]

[0082] Analysis of Table 3 reveals the relationship between the laser optical axis and the coordinates of the laser measurement platform. x axis, y shaft and z The measurement error of the included angle of the axis and the resulting laser footpoint positioning error both show a linear relationship; among them, the laser optical axis and the coordinate system of the laser measurement platform... x shaft and y The measurement error of the included angle of the axis mainly affects the planar positioning accuracy of the laser footpoint, and has a negligible impact on the elevation accuracy of the footpoint. When the included angle measurement error reaches 5 arcseconds and the planar error of the footpoint exceeds 12m, the resulting elevation error of the footpoint positioning will not exceed 5cm; and the coordinate system of the laser optical axis and the measurement platform... z The measurement error of the included angle of the axis only affects the elevation accuracy of the foot point positioning, and its impact on the plane position of the foot point positioning is negligible.

[0083] ③ Analysis of the impact of satellite attitude measurement error on laser footpoint positioning error

[0084] The satellite platform attitude is measured by independent star sensors and gyroscopes, and is independent of orbital position, laser ranging, and the angle between the laser optical axis and the coordinate system of the measurement platform. The simulation calculation of the laser footpoint positioning error caused by the three-axis attitude angle measurement error of the satellite platform is shown in Table 4.

[0085] Table 4. Simulation results of laser footpoint positioning error caused by satellite attitude angle measurement error

[0086]

[0087] Analysis of Table 4 reveals a linear correlation between satellite attitude angle measurement error and laser altimeter footpoint positioning error. Attitude angle measurement error primarily affects the laser footpoint's planar positioning accuracy. A 1-arc-second measurement error in the side yaw angle corresponds to a laser footpoint planar positioning error of approximately 2.5m, while a 1-arc-second measurement error in the pitch angle corresponds to a laser footpoint planar positioning error of approximately 2.44m. The yaw angle measurement error only affects the laser footpoint planar positioning in the X direction, with a 1-arc-second measurement error corresponding to a planar error of approximately 1.53m. Attitude angle measurement error also affects the laser footpoint positioning elevation accuracy; a 3-arc-second measurement error in the side yaw angle can result in an elevation error of approximately 10.7cm.

[0088] ④ Analysis of the impact of satellite positioning error on laser footpoint positioning error

[0089] The satellite achieves orbital positioning by carrying an independent GPS device, which is independent of laser ranging, the angle between the laser optical axis and the coordinate system of the measurement platform, and satellite attitude measurement. The simulation calculation of the laser footpoint positioning error caused by the orbital position measurement error is shown in Table 5 below:

[0090] Table 5. Simulation results of laser footpoint positioning error caused by satellite three-axis positioning error

[0091]

[0092] Table 5 also shows a linear correlation between the measurement error of the satellite orbit position (within the ICRF framework) and the resulting laser footpoint positioning error. x direction and z Directional measurement errors have a significant impact on the elevation accuracy of laser footpoint positioning, and the satellite orbit position can be calculated. x direction, y direction, z A 10cm measurement error in the direction can lead to errors of approximately 6cm, 0.8cm, and 7.9cm in the elevation direction of laser footpoint positioning.

[0093] In some embodiments of the present invention, step S101 includes:

[0094] Based on the satellite laser altimeter echo theory, discrete full waveform data is analyzed to obtain the laser ranging error factor that affects the laser ranging error.

[0095] A satellite laser ranging error model is established by performing simulation calculations based on the laser ranging error factor.

[0096] In a specific embodiment of the present invention, based on the satellite laser altimeter echo theory, it is assumed that the surface contour within the laser footprint satisfies an ergodic pattern, and the echo waveform is related to the distribution of surface topographic undulations within the footprint. When the laser altimeter system is obliquely incident on the sloping surface, such as... Figure 3 As shown, Figure 3 This is a schematic diagram of a laser altimeter system incident obliquely on a sloped surface. and These are the terrain slope angles within the footprint, parallel and perpendicular to the satellite's flight direction, respectively. The point represents the location of the satellite; This refers to the laser pointing angle; The altitude of the satellite above the Earth's surface; For about planar position The topographic relief analytical function. Geometric physical modeling of the relationship between the echo waveform and the target topographic features is performed. Factors affecting the pulse width of the laser echo include the laser altimeter system itself, the surface slope (aspect) roughness, beam curvature, beam pointing angle and divergence angle. At this time, the mean square pulse width of the full waveform laser altimeter system echo can be expressed as shown in formula (3):

[0097] (3)

[0099] In the formula, , and These are the laser echo pulse width, the laser emission pulse width, and the detector pulse response pulse width, respectively. The laser pointing angle (the angle between the laser optical axis and the nadir direction); This refers to the laser divergence angle; The speed at which light travels in a vacuum; This refers to the satellite's orbital altitude. and The terrain slope angle within the footprint is parallel and perpendicular to the satellite's flight direction; denoted as root mean square roughness.

[0100] The variance expression of the time centroid of the echo signal is shown in formula (4):

[0101] (4)

[0102] In the formula, Echo time center of gravity; The mean square pulse width of the echo; The noise factor of the photodetector is approximately 1. The number of photons contained in the echo; The number of photons for background noise; This is the detector's dark current noise; For detector thermal noise; To amplify noise in the detector's preamplifier circuit; The detector integration time; The sampling time resolution of the echo waveform; The signal-to-noise ratio for speckle is ; The mean square roughness of the terrain within the footprint; This refers to the laser pointing angle; The slope of the terrain within the footprint along the track direction; The slope of the terrain within the footprint in the direction of the vertical rail; This refers to the laser divergence angle; The speed of light in a vacuum is 299,792,458 m / s; The altitude of the satellite above the Earth's surface; The laser pointing uncertainty along the track direction; The laser pointing uncertainty is in the direction perpendicular to the rail. The area of ​​the detector's receiving aperture; is the laser wavelength.

[0103] The first term in formula (4) is the time centroid error caused by the transmission pulse time centroid error and the detector sampling noise; the second term is the time centroid error caused by background noise, detector dark thermal noise, dark current noise and preamplifier circuit amplification noise; the third term is the time centroid error caused by terrain roughness; the fourth term is the time centroid error caused by beam curvature; the fifth term is the time centroid error caused by non-nadir direction measurement and terrain slope; the sixth term is the time centroid error caused by laser pointing jitter. For the full waveform satellite laser altimetry system, the ranging error caused by detector sampling noise and transmission 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 error can be derived from formulas (3) and (4) to obtain formula (5):

[0104] (5)

[0106] It can be seen that, in order to calculate this ranging error, accurate slope information of the terrain within the footprint is required. and However, from formulas (3) and (5), it can be found that the terrain slope and other information within the laser footprint not only cause the echo pulse width to broaden, but also, together with the laser pointing angle jitter and the laser non-nadir direction measurement, cause laser ranging error. That is, the laser ranging error factor needs to be determined. Therefore, in this embodiment of the invention, an empirical model of terrain feature parameters (slope aspect, roughness) - echo pulse width broadening - laser ranging error can be established, namely, the satellite laser ranging error model, to accurately evaluate the laser ranging error value caused by laser pointing angle jitter, surface slope aspect within the footprint, and non-nadir direction measurement.

[0107] Formula (3) can be used to express the pulse width broadening caused by topographic factors (slope aspect, roughness) as shown in Formula (6):

[0108] (6)

[0110] In the formula, This refers to the laser echo pulse width. This refers to the laser emission pulse width; The pulse width is the detector's pulse response.

[0111] By simulating the laser ranging error caused by terrain factors, laser pointing jitter, and laser non-nadir direction measurement, as well as the echo pulse width broadening simulation calculation, the formula for the satellite laser ranging error model can be established as shown in formula (7):

[0112] (7)

[0113] In the formula, , , The fitting parameters and the fitting error evaluation index are: , .

[0114] From formulas (4), (5), (6) and (7), the time variance of satellite laser altimetry caused by a combination of factors such as transmission pulse time centroid error, detector sampling noise, terrain slope (aspect), roughness, beam curvature, laser non-nadir direction measurement, and laser pointing angle jitter is shown in formula (8):

[0115] (8)

[0117] In the formula, Echo time center of gravity; This refers to the laser echo pulse width. This refers to the laser emission pulse width; The pulse width of the detector's impulse response; This refers to the laser pointing angle; This refers to the laser divergence angle; The speed at which light travels in a vacuum; The altitude of the satellite above the Earth's surface; , , These are the fitting parameters; The noise factor of the photodetector; The number of photons contained in the echo; The sampling time resolution of the echo waveform; The mean square pulse width of the echo; The signal-to-noise ratio is for speckle patterns.

[0118] The distance measurement error is calculated as shown in formula (9):

[0119] (9)

[0120] In the formula, The speed at which light travels in a vacuum; Variance of satellite laser altimetry timing.

[0121] In some embodiments of the present invention, such as Figure 4 As shown, step S102 includes:

[0122] S401. Analyze the discrete full waveform data to obtain the laser echo pulse width, laser emission pulse width, and detector pulse response pulse width.

[0123] S402. Calculate the laser echo pulse width, laser emission pulse width, and detector pulse response pulse width according to the time variance calculation formula of the satellite laser ranging error model to obtain the satellite laser altimetry time variance.

[0124] S403. Calculate the variance of satellite laser altimetry based on the ranging error calculation formula of the satellite laser ranging error model to obtain the laser ranging error value.

[0125] In a specific embodiment of the present invention, the angles between the laser optical axis and the three axes of the laser measurement platform coordinate system, the satellite attitude angle, and the satellite orbit position in ①, ②, ③, and ④ above are all measured by independent devices. For example, the satellite attitude data is measured by an on-board attitude sensor, and the orbit position data is measured by an orbit positioning sensor. After being transmitted down to the ground, the data undergoes precise attitude determination and precise orbit determination processing to output precise attitude and precise orbit data, etc. The measurement errors of these elements and the laser footpoint positioning elevation errors caused by laser ranging errors are independent of each other. Combining the satellite laser ranging error model and the analysis results of steps ①, ②, ③, and ④, each measurement error and the laser footpoint positioning elevation error caused by it all show a linear correlation. 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 by the laser emitting device. These can all be obtained by measurement. The discrete full waveform data can be input into formula (8) to calculate the satellite laser altimetry variance. Then the satellite laser altimetry variance can be input into formula (9) for calculation. The satellite laser ranging error model can output the laser ranging error value.

[0126] In some embodiments of the present invention, the error factors also include laser optical axis pointing error, satellite attitude measurement error, and satellite positioning error; sensor data includes the angles between the laser optical axis and the three axes of the laser measurement platform coordinate system, satellite attitude angle, satellite orbital position, and ranging distance; step S103 includes:

[0127] The laser optical axis pointing error value, the satellite attitude measurement error value, and the satellite positioning error value are obtained.

[0128] The elevation of the laser foot point is obtained based on the included angle of the three axes, the satellite attitude angle, the satellite orbital position, and the ranging distance;

[0129] Based on the comprehensive model of elevation error in satellite laser altimetry footpoint positioning, the laser ranging error, laser optical axis pointing error, satellite attitude measurement error, and satellite positioning error are calculated to obtain the comprehensive elevation error value of satellite laser footpoint positioning.

[0130] In a specific embodiment of the present invention, based on the analysis of ①, ②, ③ and ④ above, it can be determined that the factors affecting the error also include the laser optical axis pointing error, the satellite attitude measurement error, and the satellite positioning error. The error values ​​of these errors can be obtained in other ways. For example, the test personnel can obtain the error values ​​of these errors based on the data or other data. The specific values ​​can be set according to the actual situation. The present invention does not limit these error values. A comprehensive model of satellite laser altimetry footpoint positioning elevation error can also be set. The comprehensive model of satellite laser altimetry footpoint positioning elevation error can be used to process the three-axis angle, satellite attitude angle, satellite orbit position and ranging distance obtained by the satellite sensor, and calculate the laser footpoint elevation. For example, it is assumed that the laser footpoint elevation calculation formula can be expressed as shown in formula (10):

[0131] (10)

[0132] 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 formula (11) of the satellite laser altimeter footpoint positioning elevation error comprehensive model to calculate the satellite laser footpoint positioning elevation comprehensive error value. Formula (11) is shown below:

[0133] (11)

[0135] in:

[0136] , ,

[0137]

[0138] In the formula, The comprehensive error value for satellite laser footprint positioning elevation; Elevation of the laser footpoint; Satellite orbital position x, y, z Measurements along the axial direction; For the satellite's orbital position after precise orbit determination x, y, z Positioning information along the axis; For satellite orbital position x, y, z Satellite positioning error value along the axis; This refers to the measured value of the satellite's attitude angle; The three-axis attitude angles of the satellite after precise attitude determination; The coordinates of the laser optical axis and the laser measurement platform x, y, z The measured value of the included angle along the axial direction; The coordinates of the laser optical axis and the laser measurement platform x, y, z The laser optical axis pointing error value at the included angle in the axial direction; Laser ranging error value

[0139] This invention first analyzes the factors affecting laser ranging accuracy and establishes an empirical model for laser ranging errors caused by uncorrectable error factors such as non-nadir laser measurement, laser pointing jitter error, and surface target characteristics. Specifically, by simulating the echo pulse width broadening and ranging error caused by terrain factors, a satellite laser ranging error model is established, 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 are discussed and error simulation calculations are performed. The correlation between the elevation errors caused by different factors is analyzed. Finally, a comprehensive error formula for 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 to achieve accurate analysis of the elevation accuracy of the satellite laser altimetry footpoint positioning.

[0140] Furthermore, such as Figure 5 As shown, the experimental area, taking a specific location as an example, encompasses various terrains such as plains, hills, mountains, and canyons. The experimental data includes real laser altimetry data from Gaofen-7 and high-precision airborne point cloud data, such as... Figure 5 The blue dots shown represent laser footprints; the average spatial resolution of the airborne laser point cloud is 1m, with horizontal and vertical accuracies of 0.5m and 0.2m, respectively. A special note regarding the timeliness of the validation data (airborne point cloud): Environmental facilities related to daily life in the experimental area, such as urban buildings, roads, fields, and residences, are subject to slower updates and renovations. Therefore, the time difference between the acquisition of the airborne point cloud and the transit laser altimetry data in such areas can be considered to have a relatively small impact on the evaluation of the elevation accuracy of the laser altimetry footpoints. However, the time difference between the acquisition of the airborne point cloud and the transit laser altimetry data in forest areas will significantly affect the evaluation of altimetry accuracy. Therefore, laser altimetry points located in forest areas will not be included when evaluating the accuracy of the laser altimetry point elevation error analysis.

[0141] Based on spaceborne laser altimetry data collected during six periods of the Gaofen-7 satellite's transit over the experimental area, this embodiment of the invention uses only laser altimetry data containing only one component from the laser altimetry echo waveform decomposition. Specifically, laser 1 and laser 2 have 87 and 85 laser points, respectively. After removing laser points falling in forest areas, 80 and 76 remain, respectively. The experiment first uses the laser altimetry error analysis model to calculate the elevation error of the laser altimetry points. Then, high-precision airborne point clouds are used to verify the elevation error of the laser altimetry points; the latter can be considered a true error evaluation of the laser altimetry points. Finally, the error evaluation results of the two methods are analyzed and compared. The specific accuracy verification results are as follows: Figure 6 and Figure 7 As shown, the horizontal axis represents the elevation error value of the laser footpoint positioning obtained by analyzing the satellite laser altimetry elevation error analysis model established using the embodiments of the present invention, and the vertical axis represents the error evaluation value of the laser footpoint positioning elevation using high-precision airborne laser point cloud. Figure 6 and Figure 7 Scatter plots showing the analysis results of the laser altimeter footpoint elevation error model for laser altimeter lasers 1 and 2 on the Gaofen-7 satellite and the verification results of the airborne point cloud error. Figure 6 Scatter plot for accuracy verification of the elevation error analysis model of the laser altimeter footpoint of laser 1; Figure 7 Scatter plot for verifying the accuracy of the elevation error analysis model of the laser altimeter footpoint of laser 2.

[0142] It can be observed that the error analysis results of the spaceborne laser altimetry error analysis model are in good agreement with the error verification results of the airborne point cloud. Figure 6 In the process, the maximum elevation error of the laser altimeter collected by the Gaofen-7 laser 1, as verified by the airborne point cloud, was 2.92m. At this time, the elevation error of the laser foot point positioning obtained by the spaceborne laser altimeter error analysis model was 2.87m, with a difference of only 0.05m. Figure 7 In the experiment, verified by airborne point cloud data, the maximum elevation error of the laser altimeter collected by laser 2 was 2.56m. At this point, the elevation error of the laser footpoint positioning obtained from the spaceborne laser altimeter error analysis model was 2.27m, a difference of only 0.29m. The accuracy of the spaceborne laser altimeter error model established in this paper was evaluated using the accuracy evaluation indices Mean Absolute Error (MAE) and Root Mean Square Error (RMSE), as shown in Table 6.

[0143] Table 6. Accuracy Evaluation of the Elevation Error Analysis Model for Laser Altimetry Footpoint Positioning on Gaofen-7 Satellite

[0144]

[0145] Experiments show that the satellite laser altimetry error analysis model established in this embodiment of the invention can perform quantitative error analysis on the positioning elevation of the footpoints in the full-waveform satellite laser altimetry. The accuracy of the elevation analysis of the satellite laser altimetry error analysis model established in this embodiment of the invention is evaluated using accuracy evaluation indicators. The error analysis model has an accuracy of 0.2538m (MAE) and 0.2325m (RMSE) for the footpoint coordinate elevation of Gaofen-7 laser 1, an accuracy of 0.2538m (MAE) and 0.2325m (RMSE) for the footpoint coordinate elevation of Gaofen-7 laser 2, and an overall accuracy of 0.2876m (MAE) and 0.3353m (RMSE) for the Gaofen-7 footpoint coordinate elevation error analysis.

[0146] To better implement the satellite laser altimeter footpoint positioning elevation error analysis method in this embodiment of the invention, correspondingly, this embodiment of the invention also provides a satellite laser altimeter footpoint positioning elevation error analysis device, such as... Figure 8 As shown, the satellite laser altimeter footpoint positioning elevation error analysis device 800 includes:

[0147] The data acquisition module 801 is used to acquire sensor data from the satellite sensor and discrete full waveform data of the laser transmitted by the satellite laser altimeter, establish a satellite laser ranging error model, and determine the error factors that affect the error; the error factors include laser ranging error.

[0148] The error value calculation module 802 is used to input discrete full waveform data into the satellite laser ranging error model to obtain the laser ranging error value.

[0149] The elevation error calculation module 803 is used to obtain the comprehensive elevation error value of satellite laser footpoint positioning based on sensor data and laser ranging error value.

[0150] The satellite laser altimeter footpoint positioning elevation error analysis device 800 provided in the above embodiments can realize the technical solutions described in the above embodiments of the satellite laser altimeter footpoint positioning elevation error analysis method. The specific implementation principles of each module or unit can be found in the corresponding content in the above embodiments of the satellite laser altimeter footpoint positioning elevation error analysis method, which will not be repeated here.

[0151] like Figure 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. Figure 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.

[0152] In some embodiments, memory 902 may be an internal storage unit of electronic device 900, such as a hard disk or memory of electronic device 900. In other embodiments, memory 902 may also be an external storage device of electronic device 900, such as a plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, etc. equipped on electronic device 900.

[0153] Furthermore, the memory 902 may include both internal storage units of the electronic device 900 and external storage devices. The memory 902 is used to store application software and various types of data installed on the electronic device 900.

[0154] In some embodiments, processor 901 may be a central processing unit (CPU), a microprocessor, or other data processing chip, used to run program code stored in memory 902 or process data, such as the satellite laser altimeter footpoint positioning elevation error analysis method of the present invention.

[0155] In some embodiments, display 903 may be an LED display, a liquid crystal display, a touch-sensitive liquid crystal display, or an OLED (Organic Light-Emitting Diode) touchscreen. Display 903 is used to display information from electronic device 900 and to display a visual user interface. Components 901-903 of electronic device 900 communicate with each other via a system bus.

[0156] In some embodiments of the present invention, when the processor 901 executes the satellite laser altimeter positioning elevation error analysis program in the memory 902, the following steps can be implemented:

[0157] Acquire sensor data from satellite sensors and discrete full waveform data of laser light transmitted by satellite laser altimeters, establish a satellite laser ranging error model, and determine the factors affecting the error; the factors affecting the error include laser ranging error.

[0158] The discrete full waveform data is input into the satellite laser ranging error model to obtain the laser ranging error value.

[0159] Based on sensor data and laser ranging error values, the comprehensive error value of satellite laser footpoint positioning elevation is obtained.

[0160] 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 functions mentioned above, it can also perform other functions, as detailed in the description of the corresponding method embodiments above.

[0161] Furthermore, this embodiment of the invention does not specifically limit the type of electronic device 900 mentioned. Electronic device 900 can be a mobile phone, tablet computer, personal digital assistant (PDA), wearable device, laptop computer, or other portable electronic device. Exemplary embodiments of portable electronic devices include, but are not limited to, portable electronic devices running iOS, Android, Microsoft, or other operating systems. The aforementioned portable electronic device can 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 invention, electronic device 900 may not be a portable electronic device, but rather a desktop computer with a touch-sensitive surface (e.g., a touch panel).

[0162] Accordingly, this application also provides a computer-readable storage medium for storing computer-readable programs or instructions. When the programs or instructions are executed by a processor, they can implement the steps or functions of the satellite laser altimeter footpoint positioning elevation error analysis method provided in the above-described method embodiments.

[0163] Those skilled in the art will understand that all or part of the processes of the methods described in the above embodiments can be implemented by a computer program instructing related hardware (such as a processor, controller, etc.), and the computer program can be stored in a computer-readable storage medium. The computer-readable storage medium may be a disk, optical disk, read-only memory, or random access memory, etc.

[0164] The above provides a detailed description of the satellite laser altimeter footpoint positioning elevation error analysis method, apparatus, equipment, and medium provided by the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for analyzing the height error of a satellite laser altimetry foot point positioning, characterized in that, The method comprises the following steps: acquiring sensor data of a satellite sensor and discrete full waveform data of laser sent by a satellite laser altimeter, establishing a satellite laser ranging error model, and determining an error influencing factor; the error influencing factor comprises a laser ranging error; 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; obtaining a satellite laser foot point positioning height comprehensive error value according to the sensor data and the laser ranging error value; the step of establishing the satellite laser ranging error model comprises: analyzing the discrete full waveform data based on a satellite laser altimetry echo theory to obtain a laser ranging error influencing factor of the laser ranging error; performing simulation calculation according to the laser ranging error influencing factor to establish the satellite laser ranging error model.

2. The method according to claim 1, wherein 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 a laser echo pulse width, a laser emission pulse width and a detector pulse response pulse width; calculating the laser echo pulse width, the laser emission pulse width and the detector pulse response pulse width according to a time measurement variance calculation formula of the satellite laser ranging error model to obtain a satellite laser altimetry time measurement variance; calculating the satellite laser altimetry time measurement variance according to a ranging error calculation formula of the satellite laser ranging error model to obtain the laser ranging error value of the laser ranging error.

3. The method of claim 1, wherein, the error influencing factor further comprises a laser optical axis internal pointing error, a satellite attitude measurement error and a satellite positioning error; the sensor data comprises three-axis included angles of laser optical axes and a laser measurement platform coordinate system, satellite attitude angles, satellite orbit positions and ranging distances; the step of obtaining the satellite laser foot point positioning height comprehensive error value according to the sensor data and the laser ranging error value comprises: acquiring a laser optical axis internal pointing error value of the laser optical axis internal 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 a laser foot point height according to the three-axis included angles, the satellite attitude angles, the satellite orbit positions and the ranging distances; calculating 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 according to a satellite laser altimetry foot point positioning height error comprehensive model to obtain the satellite laser foot point positioning height comprehensive error value.

4. The method of claim 2, wherein, the time measurement variance calculation formula is: wherein echo time center of gravity; is the laser echo pulse width; is the laser launch pulse width; is the detector impulse response pulse width; is the laser pointing angle; is the laser divergence angle; is the speed of light in vacuum; is the satellite to ground height; , , is the fitting parameter; is the photo detector noise factor; is the number of photons contained in the echo; is the echo waveform sampling time resolution; is the echo mean square pulse width; is the speckle signal to noise ratio.

5. The method of claim 2, wherein, the ranging error calculation formula is: wherein is the speed of light in vacuum; is the variance of the satellite laser altimetry and timing.

6. A device for analyzing the height error of a satellite laser altimetry foot point, characterized in that, The method comprises the following steps: a data acquisition module is configured to acquire sensor data of a satellite sensor and discrete full waveform data of laser sent by a satellite laser altimeter, establish a satellite laser ranging error model, and determine an error influencing factor; the error influencing factor comprises a laser ranging error; an error value calculation module is configured to input the discrete full waveform data into the satellite laser ranging error model to obtain a laser ranging error value of the laser ranging error; An elevation error calculation module is configured to obtain a satellite laser foot point positioning elevation comprehensive error value according to the sensor data and the laser ranging error value. The satellite laser ranging error model comprises: Based on the satellite laser altimetry echo theory, the discrete full waveform data is analyzed to obtain a laser ranging error factor affecting the laser ranging error; According to the laser ranging error factor, simulation calculation is performed to establish the satellite laser ranging error model.

7. An electronic device, comprising: The method comprises: A processor, a memory, and a computer program stored on the memory and capable of running on the processor, wherein the computer program, when executed by the processor, implements the steps of the satellite laser altimetry foot point positioning elevation error analysis method according to any one of claims 1-5.

8. A computer-readable storage medium, characterized in that, The computer program is stored on the computer readable storage medium, and when executed by the processor, implements the steps of the satellite laser altimetry foot point positioning elevation error analysis method according to any one of claims 1-5.

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