Satellite-borne photon counting lidar footprint positioning method and device

Abstract

The application discloses a spaceborne photon counting laser radar footprint positioning method and device, and the method comprises the following steps: generating a spaceborne pseudo waveform according to system parameters and observation data of the spaceborne photon counting laser radar; generating an airborne reference waveform according to prior terrain data of the airborne laser radar; calculating a waveform matching correlation coefficient accumulation matrix of multiple laser footprints according to the airborne reference waveform and the spaceborne pseudo waveform; and obtaining a laser footprint plane positioning coordinate corresponding to a maximum waveform matching correlation coefficient accumulation value by traversing the waveform matching correlation coefficient accumulation matrix of the multiple laser footprints. The application can effectively eliminate system errors of periodic changes over time of a laser pointing angle caused by platform vibration, temperature fluctuations, atmospheric refraction and turbulence effects during on-orbit operation of the spaceborne photon counting laser radar, so that the measured position of the laser footprint plane landing point is consistent with the real position, and the positioning precision is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of laser remote sensing, and particularly relates to a footprint positioning method and device for a spaceborne photon counting laser radar. BACKGROUND

[0002] The spaceborne ground observation laser radar is an active measuring device, which continuously emits laser pulses to a measured target. By measuring the time of flight of the laser pulses, combined with the position and attitude information of the laser radar platform, the three-dimensional geographic coordinates of the measured target can be accurately obtained. At present, the working system of the spaceborne ground observation laser radar generally includes two kinds of full waveform system and photon counting system. The spaceborne photon counting laser radar has narrower pulse width, smaller laser divergence angle and lower energy requirement, which helps to improve the laser ranging accuracy and the spatial resolution of the laser footprint, and is easy to realize the system scheme of multiple beams and high repetition frequency. At the same time, the spaceborne photon counting laser radar can obtain dense photon point cloud data in the satellite along the track direction (as shown in FIG. 1), so that it has unique advantages in earth mapping, vegetation survey, sea surface height inversion and global environmental parameter monitoring. Therefore, the spaceborne photon counting laser radar with multiple beams, high repetition frequency and micro pulses has become the development direction of the new generation of laser radars. Figure 1

[0003] The geometric positioning accuracy of the laser footprint of the spaceborne photon counting laser radar is affected by the laser radar system hardware, atmospheric environment and measured target, and the initial positioning accuracy is far from meeting the requirements of the application scene. The fine processing algorithm of the spaceborne photon counting laser radar data can greatly eliminate the laser footprint height error caused by the atmospheric delay, time synchronization, solid tide and the like. However, the platform vibration, temperature fluctuation, atmospheric refraction and turbulence effect during the on-orbit operation of the spaceborne photon counting laser radar will cause the laser pointing angle to have a periodic change error with time, resulting in that the measured position of the planar landing point of the laser footprint deviates from its true position. The planar landing point deviation of the laser footprint is usually composed of two parts of the footprint plane positioning system error and the plane positioning random error, and the value is in the range of several meters to tens of meters. SUMMARY

[0004] To solve the problems in the prior art, the application provides a footprint positioning method and device for a spaceborne photon counting laser radar, which can effectively eliminate the system error of the laser pointing angle caused by the platform vibration, temperature fluctuation, atmospheric refraction and turbulence effect during the on-orbit operation of the spaceborne photon counting laser radar, so that the measured position of the planar landing point of the laser footprint is consistent with the true position, and the positioning accuracy is improved.

[0005] To achieve the above purpose, the technical scheme adopted by the application is:

[0006] ​Firstly, a method for locating footprints using a spaceborne photon-counting lidar is provided, comprising: acquiring system parameters and observation data of the spaceborne photon-counting lidar; generating a spaceborne pseudo-waveform based on the system parameters and observation data of the spaceborne photon-counting lidar; acquiring prior terrain data of the airborne lidar; generating an airborne reference waveform based on the prior terrain data of the airborne lidar; calculating a cumulative matrix of waveform matching correlation coefficients of multiple laser footprints based on the airborne reference waveform and the spaceborne pseudo-waveform; and traversing the cumulative matrix of waveform matching correlation coefficients of multiple laser footprints to obtain the planar positioning coordinates of the laser footprints corresponding to the maximum cumulative value of the waveform matching correlation coefficients.

[0007] Furthermore, the system parameters of the spaceborne photon counting lidar include: the diameter of the laser footprint, the distance between the laser footprints along the track, and the time-domain waveform of the emitted laser pulse; the observation data of the spaceborne photon counting lidar include: the distance and elevation of the photon point cloud along the track, the length of the distance along the track, and the geographical coordinates of the photon point cloud in the track and perpendicular directions.

[0008] Furthermore, based on the observation data from the spaceborne photon counting lidar, spaceborne pseudo-waveforms are generated, including:

[0009] Photon point cloud data within the range of each laser footprint were selected. ,in, and Let represent the distance along the track and the elevation of the j-th photon point within the range of the i-th laser footprint, respectively;

[0010] The elevation of the j-th photon point within the range of the i-th laser footprint. Divide the data into several layers and obtain the elevation values ​​of the photon point cloud for each layer. :

[0011] ;

[0012] in, for The minimum value, Indicates elevation resolution. This indicates the number of layers in the photon point cloud elevation data;

[0013] Statistical analysis of two adjacent elevation strata The number of point clouds is used to generate a photon histogram. :

[0014] ;

[0015] in, Represents photon point arithmetic, subscript Indicates the first Photon histogram of a laser footprint The interval index;

[0016] With the first Centered on the first laser footprint, the second... Photon histogram within the range of a laser footprint Assign Gaussian weights and accumulate to produce the first... The pseudo-echo of a laser footprint :

[0017] ;

[0018] in, This indicates the total number of footprints within the radius of the laser footprint. This represents the root mean square radius of the laser footprint. Indicates the serial number of the laser footprint, subscript Indicates the serial number of the laser footprint. Indicates the total number of laser footprints. Indicates the length of the distance along the track. Indicates the spacing between laser footprints along the track;

[0019] Pseudo-echoes from multiple footprints Generates spaceborne pseudo waveforms :

[0020] ;

[0021] in, This indicates the number of laser footprints accumulated over the distance along the track. This indicates the sequence number of the laser footprints within the cumulative range.

[0022] Furthermore, the prior terrain data of the airborne lidar includes the three-dimensional coordinates of the target points.

[0023] Furthermore, based on the prior terrain data from the airborne lidar, an airborne reference waveform is generated, including:

[0024] Set the coordinates of the airborne reference waveform search point :

[0025] ;

[0026] in, Indicates the first The geographical coordinates of a laser footprint on the vertical rail and along the rail direction; Represents the matrix grid spacing; subscript Indicates the search point number along the satellite's orbit. This indicates the search point number along the vertical rail direction. This indicates the rounding up operation;

[0027] Using the set airborne reference waveform search point coordinates Centered on the track, set the coordinates of the accumulation point within the accumulated distance along the track. :

[0028] ;

[0029] Among them, subscript Indicates the index of the accumulated point coordinates;

[0030] Get the coordinates of the accumulated point echo at location ;

[0031] Accumulate echo data from multiple laser footprints The coordinates of the search point are obtained. Airborne reference waveform at location :

[0032] .

[0033] Furthermore, obtain the coordinates of the accumulated points. echo at location ,include:

[0034] Accumulated point coordinates Centered on the laser footprint, the planar coordinates of the airborne prior terrain data within the range were selected. , where subscript Indicates the index number of the airborne prior terrain data;

[0035] Energy weights of computer-loaded prior terrain data :

[0036] ;

[0037] The elevation coordinates of the airborne prior terrain data within the laser footprint range. Divide into several layers and obtain the elevation value of each layer. :

[0038] ;

[0039] in, for The minimum value, This indicates the number of layers in the elevation data;

[0040] Statistical analysis of two adjacent elevation strata The energy weights are summed to generate the target waveform. :

[0041] ;

[0042] where subscript i represents the index number of each layer of airborne prior terrain data, , satisfies:

[0043] ;

[0044] wherein, represents the diameter of the laser footprint;

[0045] The target waveform is convolved with the time-domain waveform of the transmitted laser pulse to obtain the echo at the cumulative point coordinate :

[0046] ;

[0047] wherein, represents the time-domain waveform of the transmitted laser pulse, and the symbol represents a convolution operation.

[0048] Further, a waveform matching correlation coefficient cumulative matrix of multiple laser footprints is calculated, including:

[0049] The spaceborne pseudo waveform and the airborne reference waveform are normalized to obtain the normalized spaceborne pseudo waveform and the normalized airborne reference waveform :

[0050] ;

[0051] ;

[0052] The correlation coefficient of the normalized spaceborne pseudo waveform and the normalized airborne reference waveform is calculated to obtain the waveform matching correlation coefficient matrix corresponding to the i-th laser footprint:

[0053] ;

[0054] wherein the correlation coefficient satisfies:

[0055] ;

[0056] wherein, represents a covariance operation, and respectively represent the normalized spaceborne pseudo waveform​​​ and the on-board reference waveform ;

[0057] with a search step , a plurality of laser footprint waveform matching correlation coefficient matrixes are selected , and a plurality of laser footprint waveform matching correlation coefficient accumulation matrixes are obtained by summation :

[0058] ;

[0059] wherein, n represents the search step , and m represents the corresponding number of footprint intervals , , represents the total number of laser footprints used in pseudo waveform matching.

[0060] Further, the laser footprint planar positioning coordinates corresponding to the maximum value of the waveform matching correlation coefficient accumulation value are obtained by traversing the plurality of laser footprint waveform matching correlation coefficient accumulation matrixes, including:

[0061] the matrix row number and the column number corresponding to the maximum value in the plurality of laser footprint waveform matching correlation coefficient accumulation matrixes , and the system errors of the laser footprints in the vertical rail direction and the along-rail direction are calculated and :

[0062] ;

[0063] ;

[0064] wherein, abs represents the absolute value operation;

[0065] the positioning coordinates of each laser footprint in the vertical rail direction and the along-rail direction are corrected, and the planar positioning coordinates of the corrected laser footprint are obtained :

[0066] ;

[0067] .

[0068] In a second aspect, a satellite-borne photon counting laser radar footprint positioning device is provided, comprising: a satellite-borne radar data acquisition module, configured to acquire system parameters and observation data of the satellite-borne photon counting laser radar; a satellite-borne pseudo-waveform generation module, configured to generate a satellite-borne pseudo-waveform according to the system parameters and the observation data of the satellite-borne photon counting laser radar; an airborne radar data acquisition module, configured to acquire prior terrain data of the airborne laser radar; an airborne reference waveform generation module, configured to generate an airborne reference waveform according to the prior terrain data of the airborne laser radar; a waveform matching module, configured to calculate a waveform matching correlation coefficient accumulation matrix of multiple laser footprints according to the airborne reference waveform and the satellite-borne pseudo-waveform; and a positioning module, configured to traverse the waveform matching correlation coefficient accumulation matrix of the multiple laser footprints to obtain a laser footprint plane positioning coordinate corresponding to a maximum waveform matching correlation coefficient accumulation value.

[0069] Compared with the prior art, the present application has the following beneficial effects: according to the system parameters and the observation data of the satellite-borne photon counting laser radar, a satellite-borne pseudo-waveform is generated; according to the prior terrain data of the airborne laser radar, an airborne reference waveform is generated; according to the airborne reference waveform and the satellite-borne pseudo-waveform, a waveform matching correlation coefficient accumulation matrix of multiple laser footprints is calculated; and by traversing the waveform matching correlation coefficient accumulation matrix of the multiple laser footprints, a laser footprint plane positioning coordinate corresponding to a maximum waveform matching correlation coefficient accumulation value is obtained, which can effectively eliminate the system error of the periodic change of the laser pointing angle with time caused by platform vibration, temperature fluctuation, atmospheric refraction and turbulence effect during the on-orbit operation of the satellite-borne photon counting laser radar, so that the measured position of the laser footprint plane landing point is consistent with the true position, and the positioning accuracy is improved. BRIEF DESCRIPTION OF DRAWINGS

[0070] Figure 1 is a schematic diagram of photon point cloud data acquired by the satellite-borne photon counting laser radar in the along-orbit direction;

[0071] Figure 2 is a laser pulse time-domain waveform when the laser is emitted in the embodiment of the present application;

[0072] Figure 3 is a schematic diagram of a photon point cloud in the embodiment of the present application;

[0073] Figure 4 is a geographical coordinate of the photon point cloud in the along-orbit and the across-orbit directions in the embodiment of the present application;

[0074] Figure 5 is a three-dimensional coordinate of a ground object target point in the embodiment of the present application;

[0075] Figure 6 is a normalized distribution of the satellite-borne pseudo-waveform corresponding to the first laser footprint position in the embodiment of the present application;

[0076] Figure 7 is the normalized distribution of the airborne reference waveform corresponding to the first laser footprint position in the embodiment of the present application;

[0077] Figure 8 is the waveform matching correlation coefficient accumulation matrix distribution in the embodiment of the present application;

[0078] Figure 9 is the elevation residual histogram distribution before and after the laser footprint positioning correction in the embodiment of the present application, wherein (a) is the elevation residual histogram distribution before correction, and (b) is the elevation residual histogram distribution after correction. DETAILED DESCRIPTION

[0079] The present application will be further described below in conjunction with the drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and cannot be used to limit the protection scope of the present application.

[0080] Embodiment one

[0081] A spaceborne photon counting laser radar footprint positioning method, comprising: acquiring system parameters and observation data of a spaceborne photon counting laser radar; generating a spaceborne pseudo waveform according to the system parameters and observation data of the spaceborne photon counting laser radar; acquiring prior terrain data of an airborne laser radar; generating an airborne reference waveform according to the prior terrain data of the airborne laser radar; calculating a waveform matching correlation coefficient accumulation matrix of multiple laser footprints according to the airborne reference waveform and the spaceborne pseudo waveform; traversing the waveform matching correlation coefficient accumulation matrix of the multiple laser footprints to obtain laser footprint plane positioning coordinates corresponding to a maximum waveform matching correlation coefficient accumulation value.

[0082] Step 1: Acquiring system parameters and observation data of a spaceborne photon counting laser radar

[0083] 1.1, The system parameters of the spaceborne photon counting laser radar include: laser footprint diameter, laser footprint along-track spacing, and transmitted laser pulse time-domain waveform.

[0084] 1.2, The observation data of the spaceborne photon counting laser radar includes: along-track distance and elevation of the photon point cloud, along-track distance length, and geographic coordinates of the photon point cloud in the along-track and vertical-track directions.

[0085] Step 2, Generating a spaceborne pseudo waveform according to the system parameters and observation data of the spaceborne photon counting laser radar

[0086] 2.1, Selecting photon point cloud data within each laser footprint range , wherein, and represent the along-track distance and elevation of the jth photon point within the ith laser footprint range, respectively. , Let represent the distance along the track for the i-th laser footprint, and D represent the diameter of the laser footprint. (Subscript) Indicates the serial number of the laser footprint. This is the total number of laser footprints. Indicates the length of the distance along the track. Indicates the spacing of the laser footprints along the track. Indicates the sequence number of the photon point. The total number of photon data within the i-th laser footprint.

[0087] 2.2. Determine the elevation of the j-th photon point within the range of the i-th laser footprint. The image is divided into several layers based on its height, and the elevation value of the photon point cloud in each layer is obtained. :

[0088] ;

[0089] in, for The minimum value, Indicates elevation resolution. This indicates the number of layers in the photon point cloud elevation data. ,in Indicates the total number of layers:

[0090] ;

[0091] in, For the first Photon point cloud elevation data within the range of a laser footprint The maximum value, This indicates the rounding up operation.

[0092] 2.3. Statistical analysis of adjacent elevation layers The number of point clouds is used to generate a photon histogram. :

[0093] ;

[0094] in, Represents photon point arithmetic, subscript Indicates the first Photon histogram of a laser footprint The interval index, .

[0095] 2.4, with the first Centered on the first laser footprint, the second... Photon histogram within the range of a laser footprint Assign Gaussian weights and accumulate to produce the first... Pseudo echo of a laser footprint :

[0096] ;

[0097] wherein, represents the total number of footprints within the radius of the laser footprint, , represents a rounding operation towards zero, represents the root mean square radius of the laser footprint, , represents the sequence number of the laser footprint.

[0098] 2.5, Accumulating pseudo echoes of multiple footprints to generate a spaceborne pseudo waveform :

[0099] ;

[0100] wherein, represents the number of laser footprints within the accumulated distance along the track, , represents the accumulated distance along the track, represents the sequence number of the laser footprint within the accumulated range.

[0101] Step 3, Obtain prior terrain data of the airborne laser radar

[0102] The prior terrain data of the airborne laser radar comprises: three-dimensional coordinates of the ground object points.

[0103] Step 4, Generate an airborne reference waveform according to the prior terrain data of the airborne laser radar

[0104] 4.1, Set the coordinates of the search points of the airborne reference waveform :

[0105] ;

[0106] wherein, represents the geographic coordinates of the th laser footprint in the direction along the track and the direction perpendicular to the track; represents the matrix grid spacing; the subscript represents the sequence number of the search point in the direction along the track of the satellite, represents the sequence number of the search point in the direction perpendicular to the track, represents the maximum number of search points in the simulation of the airborne reference waveform.

[0107] 4.2, Set the coordinates of the accumulated points within the accumulated distance along the track with the set coordinates of the search points of the airborne reference waveform as the center:

[0108] ;

[0109] wherein subscript denotes the index number of the accumulation point coordinate.

[0110] 4.3, obtaining the accumulation point coordinate of the echo at the position , specifically comprising:

[0111] 4.3.1, selecting the plane coordinates of the airborne prior terrain data within the laser footprint range as the center of the accumulation point coordinate wherein subscript denotes the index number of the airborne prior terrain data, , , satisfying:

[0112] ;

[0113] 4.3.2, calculating the energy weight of the airborne prior terrain data :

[0114] .

[0115] 4.3.3, dividing the elevation coordinates of the airborne prior terrain data within the laser footprint range into several layers to obtain the elevation value of each layer :

[0116] ;

[0117] wherein is the minimum value of the elevation coordinates of the airborne prior terrain data within the laser footprint range , denotes the number of elevation data layers, wherein denotes the total number of elevation data layers:

[0118] ;

[0119] wherein is the maximum value of the elevation coordinates of the airborne prior terrain data within the laser footprint range .

[0120] 4.3.4, statistics of the energy weight sum within the adjacent two elevation layer slices to generate the target waveform :

[0121] ; ​

[0122] where subscript denotes the index number of each layer of airborne prior terrain data, , satisfies:

[0123] .

[0124] 4.3.5, the target waveform is convolved with the time-domain waveform of the transmitted laser pulse to obtain the echo at the coordinate of the accumulation point:

[0125] ;

[0126] where, denotes the time-domain waveform of the transmitted laser pulse, and the symbol denotes the convolution operation.

[0127] 4.4, the echo data of multiple laser footprints is accumulated to obtain the airborne reference waveform at the coordinate of the search point:

[0128] .

[0129] Step 5, according to the airborne reference waveform and the spaceborne pseudo waveform, the waveform matching correlation coefficient accumulation matrix of multiple laser footprints is calculated

[0130] 5.1, the spaceborne pseudo waveform and the airborne reference waveform are normalized to obtain the normalized spaceborne pseudo waveform and the normalized airborne reference waveform :

[0131] ;

[0132] .

[0133] 5.2, the correlation coefficient of the normalized spaceborne pseudo waveform and the normalized airborne reference waveform is calculated to obtain the waveform matching correlation coefficient matrix corresponding to the th laser footprint:

[0134] ;

[0135] where the correlation coefficient satisfies:

[0136] ​​​ ;

[0137] wherein, denotes a covariance operation, and denote the normalized standard deviations of the satellite-borne pseudo-waveform and the airborne reference waveform , respectively.

[0138] 5.3, selecting a plurality of laser footprint waveform matching correlation coefficient matrices at intervals of a search step size , and obtaining a multi-laser footprint waveform matching correlation coefficient accumulation matrix by summation:

[0139] ;

[0140] wherein, denotes a search step size corresponding to the number of footprint intervals, , denotes the total number of laser footprints used for pseudo-waveform matching.

[0141] Step 6, traversing the multi-laser footprint waveform matching correlation coefficient accumulation matrix to obtain the laser footprint planar positioning coordinates corresponding to the maximum waveform matching correlation coefficient accumulation value

[0142] 6.1, traversing the maximum value in the multi-laser footprint waveform matching correlation coefficient accumulation matrix to obtain the matrix row number and column number , and calculating the system errors of the laser footprint in the cross-track direction and the along-track direction and :

[0143] ;

[0144] ;

[0145] wherein, denotes an absolute value operation.

[0146] 6.2, correcting the positioning coordinates of each laser footprint in the cross-track direction and the along-track direction to obtain the planar positioning coordinates of the corrected laser footprint :

[0147] ;

[0148] .

[0149] Example Two

[0150] Based on the satellite-borne photon counting laser radar footprint positioning method described in embodiment one, this embodiment takes the advanced topographic laser mapping instrument (ATLAS) launched by the United States in 2018 as an example, and further specifically describes the satellite-borne photon counting laser radar footprint positioning method in combination with the drawings.

[0151] The present application takes the satellite-borne photon counting laser radar observation data and prior terrain data as input, simulates the pseudo-waveform based on the laser radar observation data and the reference waveform based on the prior terrain data, constructs the matching correlation coefficient accumulation matrix of the satellite-borne pseudo-waveform and the airborne reference waveform under the condition of multiple laser footprints, and realizes the accurate positioning of the satellite-borne photon counting laser radar footprint by searching the laser footprint plane positioning coordinates corresponding to the maximum laser footprint matching correlation coefficient accumulation value. This positioning method can be applied to the footprint positioning of cities, vegetation and rugged mountainous areas with less prior terrain data, and has low positioning cost and consumes less manpower and resources.

[0152] The initial parameters are obtained, including: obtaining the system parameters and observation data of the satellite-borne photon counting laser radar, and the prior terrain data of the airborne laser radar.

[0153] The initial parameters of the satellite-borne photon counting laser radar footprint positioning mainly include:

[0154] Parameter one, satellite-borne laser radar system parameters: laser footprint diameter, laser footprint along-track spacing, and transmitted laser pulse time-domain waveform.

[0155] Parameter two, satellite-borne laser radar photon point cloud data: along-track distance and elevation of the photon point cloud, along-track distance length, and geographic coordinates of the photon point cloud in the along-track and vertical direction.

[0156] Parameter three, satellite-borne pseudo-waveform simulation parameters: along-track cumulative distance and elevation resolution.

[0157] Parameter four, airborne laser radar prior terrain data: three-dimensional coordinates of the ground object points.

[0158] Parameter five, traversal search data: maximum search point number of the airborne reference waveform simulation, matrix grid spacing, search step distance, and total number of laser footprints used for pseudo-waveform matching.

[0159] All parameter names and numerical values are shown in Table 1.

[0160] Table 1 Initial parameters of satellite-borne photon counting laser radar footprint positioning

[0161]

[0162] Step 2, according to the system parameters and observation data of the satellite-borne photon counting laser radar, generate the satellite-borne pseudo-waveform

[0163] 2.1, select the photon point cloud data in each laser footprint range , , subscript represents the laser footprint number.

[0164] 2.2, the elevation of the jth photon point in the ith laser footprint range is divided into several layers, and the elevation value of each layer of photon point cloud is obtained :

[0165] ;

[0166] Total number of layers .

[0167] 2.3, count the number of point clouds in the adjacent two elevation layer slices , generate photon histogram :

[0168] .

[0169] 2.4, taking the ith laser footprint as the center, assigning Gaussian weight to the photon histogram in the range of the ith laser footprint and accumulating it to generate the pseudo echo of the ith laser footprint : .

[0170] .

[0171] 2.5, accumulate the pseudo echoes of multiple footprints , generate spaceborne pseudo waveform :

[0172] .

[0173] Figure 6 The normalized distribution of the spaceborne pseudo waveform corresponding to the first laser footprint position is shown.

[0174] Step 4, generate airborne reference waveform according to prior terrain data of airborne laser radar

[0175] 4.1, set the search point coordinates of the airborne reference waveform :

[0176] ;

[0177] Subscript represents the search point number in the direction along the orbit of the satellite, ​​represents the search point sequence number in the track direction.

[0178] 4.2, search point coordinates of the set airborne reference waveform Set the accumulation point coordinates within the accumulated distance along the track :

[0179] ;

[0180] wherein subscript represents the accumulation point coordinate sequence number.

[0181] 4.3, obtain accumulation point coordinates Echo at the position , specifically includes:

[0182] 4.3.1, take the plane coordinates of the airborne prior terrain data within the laser footprint range as the center wherein subscript represents the index number of the airborne prior terrain data, , satisfy:

[0183] ;

[0184] 4.3.2, calculate the energy weight of the airborne prior terrain data :

[0185] .

[0186] 4.3.3, divide the elevation coordinates of the airborne prior terrain data within the laser footprint range into several layers, and obtain the elevation value of each layer :

[0187] ;

[0188] wherein, represents the total number of elevation data layers:

[0189] ;

[0190] wherein, is the maximum value of the elevation coordinates of the airborne prior terrain data within the laser footprint range .

[0191] 4.3.4, statistics of the energy weight sum within the adjacent two elevation layer slices produce target waveform : ​​

[0192] ;

[0193] where subscript denotes the index number of each layer of airborne prior terrain data, , satisfies:

[0194] .

[0195] 4.3.5, the target waveform is convolved with the time-domain waveform of the transmitted laser pulse to obtain the echo at the accumulation point coordinate :

[0196] ;

[0197] where, denotes the time-domain waveform of the transmitted laser pulse, and the symbol denotes convolution operation.

[0198] 4.4, accumulate the echo data of multiple laser footprints to obtain the airborne reference waveform at the search point coordinate :

[0199] .

[0200] Figure 7 The normalized distribution of the corresponding airborne reference waveform at the first laser footprint position is shown.

[0201] Step 5, according to the airborne reference waveform and the spaceborne pseudo waveform, calculate the waveform matching correlation coefficient accumulation matrix of multiple laser footprints

[0202] 5.1, normalize the spaceborne pseudo waveform and the airborne reference waveform to obtain the normalized spaceborne pseudo waveform and the airborne reference waveform :

[0203] ;

[0204] .

[0205] 5.2, calculate the correlation coefficient of the normalized spaceborne pseudo waveform and the airborne reference waveform to obtain the waveform matching correlation coefficient matrix corresponding to the th laser footprint :​​

[0206] ;

[0207] wherein the correlation coefficient satisfies:

[0208] .

[0209] 5.3, select multiple laser footprint waveform matching correlation coefficient matrix with search step distance , get multiple laser footprint waveform matching correlation coefficient accumulation matrix by summation:

[0210] .

[0211] Figure 8 The waveform matching correlation coefficient accumulation matrix distribution in the embodiment is shown.

[0212] Step 6, traverse the multiple laser footprint waveform matching correlation coefficient accumulation matrix to get the laser footprint plane positioning coordinates corresponding to the maximum waveform matching correlation coefficient accumulation value

[0213] 6.1, traverse the maximum value in the multiple laser footprint waveform matching correlation coefficient accumulation matrix corresponding to the matrix row number and column number , calculate the system error of the laser footprint in the vertical rail direction and the along rail direction and :

[0214] ;

[0215] ;

[0216] Figure 8 The system error corresponding to the maximum value of the waveform matching correlation coefficient accumulation matrix is shown.

[0217] 6.2, correct the positioning coordinates of each laser footprint in the vertical rail direction and the along rail direction, get the plane positioning coordinates of the corrected laser footprint :

[0218] ;

[0219] .

[0220] Accuracy verification analysis:

[0221] The 50 laser footprints within the 87.5 m-945 m along-track distance are selected at the search step of 17.5 m, and each laser footprint position is offset by 2 m and 0.5 m in the along-track and cross-track directions, respectively, according to the system offset of the 50 laser footprints in the above embodiment, to obtain the corrected laser footprint positions. The airborne reference elevation at the laser footprint position before and after correction (the average value of the airborne point cloud elevation within the laser footprint range) is calculated, and compared with the elevation product of the Advanced Topographic Laser Swath Mapping System (ATLAS), and the elevation residual before and after the laser footprint positioning correction is quantitatively calculated. The elevation residual histogram distribution before and after the laser footprint positioning correction is shown in Figure 9 Table 2.

[0222] Table 2. Elevation residual statistics before and after correction of laser footprint position

[0223]

[0224] As can be seen from Table 2, the elevation difference indicators after the footprint positioning correction have decreased to different degrees relative to before the correction, which indicates that the footprint position of the spaceborne photon counting laser radar calculated based on the method of the application is more accurate.

[0225] Embodiment Three

[0226] Based on the spaceborne photon counting laser radar footprint positioning method described in Embodiment One and Embodiment Two, the present embodiment provides a spaceborne photon counting laser radar footprint positioning device, comprising:

[0227] a spaceborne radar data acquisition module for acquiring system parameters and observation data of the spaceborne photon counting laser radar;

[0228] a spaceborne pseudo-waveform generation module for generating a spaceborne pseudo-waveform based on the system parameters and observation data of the spaceborne photon counting laser radar;

[0229] an airborne radar data acquisition module for acquiring prior terrain data of the airborne laser radar;

[0230] an airborne reference waveform generation module for generating an airborne reference waveform based on the prior terrain data of the airborne laser radar;

[0231] a waveform matching module for calculating a waveform matching correlation coefficient accumulation matrix of multiple laser footprints based on the airborne reference waveform and the spaceborne pseudo-waveform;

[0232] a positioning module for traversing the waveform matching correlation coefficient accumulation matrix of the multiple laser footprints to obtain the laser footprint plane positioning coordinates corresponding to the maximum waveform matching correlation coefficient accumulation value.

[0233] The above merely describes the preferred embodiments of the present application, and it should be pointed out that, for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present application, and these improvements and modifications should also be considered as the protection scope of the present application.

Claims

1. A space-borne photon counting lidar foot print localization method, characterized in that, The method comprises the following steps: acquiring system parameters and observation data of a spaceborne photon counting lidar; generating a spaceborne pseudo waveform according to the system parameters and observation data of the spaceborne photon counting lidar; acquiring prior terrain data of an airborne lidar; generating an airborne reference waveform according to the prior terrain data of the airborne lidar; calculating a waveform matching correlation coefficient accumulation matrix of multiple laser footprints according to the airborne reference waveform and the spaceborne pseudo waveform; traversing the waveform matching correlation coefficient accumulation matrix of the multiple laser footprints to obtain laser footprint plane positioning coordinates corresponding to a maximum waveform matching correlation coefficient accumulation value; wherein the system parameters of the spaceborne photon counting lidar comprise a laser footprint diameter, an along-track spacing of the laser footprint, and a time-domain waveform of a laser pulse; the observation data of the spaceborne photon counting lidar comprise along-track distances and elevations of a photon point cloud, an along-track distance length, and geographic coordinates of the photon point cloud in along-track and vertical-track directions; generating the airborne reference waveform according to the prior terrain data of the airborne lidar comprises: Setting on-board reference waveform search point coordinates : ； wherein, denotes the geographic coordinates of the laser footprints in the along-track and cross-track directions; denotes the matrix grid spacing; denotes the search point index in the along-track direction, denotes the search point index in the cross-track direction, denotes the ceiling operation; N denotes the maximum number of search points for the airborne reference waveform simulation. to search point coordinates of a set airborne reference waveform to set accumulation point coordinates within an accumulated distance along the track : ； wherein subscript represents the accumulated point coordinate serial number, represents the number of laser footprints within the accumulated distance along the track, represents the laser footprint spacing along the track; acquiring accumulated point coordinates echoes at locations ; accumulating echo data of multiple laser footprints , obtaining search point coordinates onboard reference waveform at a location : ； Acquiring accumulated point coordinates Echoes at locations , comprising: with the accumulated point coordinate as the center, selecting the plane coordinates of the airborne prior terrain data within the laser footprint range wherein the subscript represents the index number of the airborne prior terrain data;​ Energy weighting of computer-borne a priori terrain data : ； wherein, represents the root mean square radius of the laser footprint, and the elevation coordinates of the airborne a priori terrain data within the laser footprint range are divided into several layers to obtain the elevation value of each layer : ； wherein is a minimum of denotes the number of elevation levels, denotes the elevation resolution; Statistical adjacent two elevation slice within the layer of the piece The energy weight and the target waveform are generated : ； wherein the subscript denotes the index number of the prior terrain data onboard for each layer, , satisfies: ； wherein, represents the laser footprint diameter; convolve the target waveform with the time-domain waveform of the emitted laser pulse to obtain accumulated point coordinates echo at the location : ； wherein denotes the time-domain waveform of the emitted laser pulse, the symbol denotes a convolution operation.

2. The space-borne photon counting lidar foot print localization method of claim 1, wherein, generating the spaceborne pseudo waveform according to the observation data of the spaceborne photon counting lidar comprises: selecting photon point cloud data within each laser footprint range wherein, and respectively represent the along-track distance and elevation of the jth photon point within the ith laser footprint range. elevation of the jth photon dot within the ith laser footprint range is divided into several layers to obtain the elevation value of each layer of photon dot cloud : ； wherein, is a minimum of denotes the number of levels of the photonic point cloud elevation data; Counting the number of point clouds within a slice adjacent to two elevation slices producing a photon histogram : ； wherein, represents a photon count operation, the subscript represents the interval number of the photon histogram of the laser footprint ; With the first laser footprint as the center, the photon histogram within the range of the first laser footprint is given a Gaussian weight and accumulated to produce the pseudo echo of the first laser footprint : ； wherein, represents the total number of footprints within the radius of the laser footprint, represents the laser footprint number, subscript represents the laser footprint number, represents the total number of laser footprints, represents the along track distance length; Cumulative multiple footprint pseudoechoes Generating space-borne pseudo-waveforms : ； wherein, represents the laser footprint number in the accumulation range.

3. The space-borne photon counting lidar foot print localization method of claim 2, wherein, the prior terrain data of the airborne lidar comprises three-dimensional coordinates of a ground object target point.

4. The space-borne photon counting lidar foot print localization method of claim 3, wherein, calculating the waveform matching correlation coefficient accumulation matrix of the multiple laser footprints comprises: a space-borne pseudo-waveform and an airborne reference waveform is normalized to obtain a normalized space-borne pseudo-waveform and an airborne reference waveform : ； ； correlation coefficient of the normalized space-borne pseudo-waveform and the airborne reference waveform , the first laser footprint corresponding waveform matching correlation coefficient matrix :​​​ ； wherein the correlation coefficient satisfies: ； wherein, denotes a covariance operation, and denotes the standard deviation of the normalized spaceborne pseudo-waveform and the airborne reference waveform respectively. With search step size For intervals, waveforms of multiple laser footprints are selected for correlation coefficient matrix matching. The waveform matching correlation coefficient accumulation matrix of multiple laser footprints is obtained by summing. : ； wherein, represents the search step size corresponding number of footprints intervals, , represents the total number of laser footprints used for the pseudo-waveform matching.

5. The space-borne photon counting lidar foot print localization method of claim 4, wherein, traversing the waveform matching correlation coefficient accumulation matrix of the multiple laser footprints to obtain laser footprint plane positioning coordinates corresponding to a maximum waveform matching correlation coefficient accumulation value comprises: Waveform matching correlation coefficient accumulation matrix of multiple laser footprints Matrix row number corresponding to the maximum value of the middle And column number , calculate the system error of the laser footprint in the vertical rail direction and along the rail direction And : ； ； wherein abs represents an absolute value operation; correcting the positioning coordinates of each laser footprint in the vertical rail direction and along the rail direction to obtain planar positioning coordinates of the corrected laser footprint : ； 。 6. A space-borne photon counting lidar foot print positioning device, characterized by, The method comprises the following steps: a spaceborne radar data acquisition module is configured to acquire system parameters and observation data of a spaceborne photon counting lidar; a spaceborne pseudo waveform generation module is configured to generate a spaceborne pseudo waveform according to the system parameters and observation data of the spaceborne photon counting lidar; an airborne radar data acquisition module is configured to acquire prior terrain data of an airborne lidar; an airborne reference waveform generation module is configured to generate an airborne reference waveform according to the prior terrain data of the airborne lidar; a waveform matching module is configured to calculate a waveform matching correlation coefficient accumulation matrix of multiple laser footprints according to the airborne reference waveform and the spaceborne pseudo waveform; a positioning module is configured to traverse the waveform matching correlation coefficient accumulation matrix of the multiple laser footprints to obtain laser footprint plane positioning coordinates corresponding to a maximum waveform matching correlation coefficient accumulation value; wherein the system parameters of the spaceborne photon counting lidar comprise a laser footprint diameter, an along-track spacing of the laser footprint, and a time-domain waveform of a laser pulse; the observation data of the spaceborne photon counting lidar comprise along-track distances and elevations of a photon point cloud, an along-track distance length, and geographic coordinates of the photon point cloud in along-track and vertical-track directions; generating the airborne reference waveform according to the prior terrain data of the airborne lidar comprises: Setting on-board reference waveform search point coordinates : ； wherein, denotes the geographic coordinates of the laser footprints in the along-track and cross-track directions; denotes the matrix grid spacing; denotes the search point number in the along-track direction, denotes the search point number in the cross-track direction, denotes the ceiling operation; N denotes the maximum number of search points for the airborne reference waveform simulation. to search point coordinates of a set airborne reference waveform to set accumulation point coordinates within an accumulated distance along the track : ； wherein subscript represents the accumulated point coordinate serial number, represents the number of laser footprints within the accumulated distance along the track, represents the laser footprint spacing along the track; acquiring accumulated point coordinates echoes at locations ; accumulating echo data of multiple laser footprints , obtaining search point coordinates onboard reference waveform at the location : ； acquiring accumulated point coordinates echoes at locations comprising: with the accumulated point coordinates as the center, the plane coordinates of the airborne prior terrain data within the laser footprint range wherein the subscript represents the index number of the airborne prior terrain data; Energy weighting of computer-borne a priori terrain data : ； wherein, represents the root mean square radius of the laser footprint, and the elevation coordinates of the airborne a priori terrain data within the laser footprint range are divided into several layers to obtain the elevation value of each layer : ； wherein is a minimum of denotes a number of elevation levels, denotes an elevation resolution; Statistical adjacent two elevation slice within the layer of the piece The energy weight and the target waveform are generated : ； wherein the subscript denotes the index number of the prior terrain data onboard for each layer, , satisfies: ； wherein, represents the laser footprint diameter; convolve the target waveform with the time-domain waveform of the emitted laser pulse to obtain accumulated point coordinates echo at the location : ； wherein denotes the time-domain waveform of the emitted laser pulse, the symbol denotes a convolution operation.

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