Ground vertical track slope inversion method and equipment based on spaceborne photon counting radar

Abstract

The present invention provides a method and device for ground vertical track slope inversion based on a spaceborne photon counting radar. The method comprises: inputting system parameters of the spaceborne photon counting radar, vertical track slope inversion control parameters, and single-track point cloud data; calculating the ground along-track slope and roughness; accumulating point cloud data to generate a photon histogram; restoring the photon histogram to a ground reflection signal; extracting the root mean square pulse width of the ground reflection signal; and resolving the ground vertical track slope. The present invention can invert the ground vertical track slope based on single-track point cloud data of a spaceborne photon counting radar. The method is applicable to single-beam and multi-beam spaceborne photon counting radars, significantly improving the resolution of ground vertical track slope inversion and enhancing the robustness of the ground vertical track slope inversion accuracy.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of laser remote sensing technology, and in particular to a ground vertical track slope inversion method and device based on a space-borne photon counting radar. Background Art

[0002] Spaceborne photon-counting radar (SPCR) is a new type of laser remote sensing device. It uses a micro-pulse, high-repetition-rate, narrow-pulse-width pulsed laser as its light source and a single-photon detector as its receiving device, capable of capturing target reflection signals at varying photon energy levels. The unique digital probabilistic response mode of the single-photon detector prevents SPCR from recording the strength of the target reflection signal, but only the discrete photon events generated by the target reflection signal. Due to the high sensitivity of SPCR, atmospheric and device noise can easily trigger the photon detector, generating noise photon events. Therefore, the photon events actually recorded by SPCR include both signal and noise photon events. By measuring the arrival time of all photon events and combining them with the satellite platform's position and attitude information and laser pointing information, SPCR can acquire high-density point cloud data along the track.

[0003] In the field of topography, the ground along-track slope and cross-track slope are important parameters for characterizing the distribution of terrain undulation. Based on high-density point cloud data from spaceborne photon counting radar in the along-track direction, the arc tangent of the slope of the best-fitting line of the point cloud data is extracted using a linear fitting method, which can be used to invert the ground along-track slope. However, there are few public reports on the inversion of ground cross-track slope based on point cloud data from spaceborne photon counting radar. The relevant methods all utilize point cloud data from adjacent strong and weak laser beam trajectories, and therefore have three limitations: First, the resolution of the cross-track slope inversion is limited by the cross-track spacing between adjacent strong and weak laser beams. The larger the cross-track spacing, the lower the resolution of the cross-track slope inversion; second, if there is a certain mutual difference between the point cloud data of adjacent strong and weak laser beam trajectories, it will affect the inversion accuracy of the cross-track slope; third, it is not applicable to the ground cross-track slope inversion of point cloud data from a single laser beam trajectory (single track). Therefore, developing a ground vertical track slope inversion method and equipment based on space-borne photon counting radar can effectively overcome the defects in the above-mentioned related technologies and has become a technical problem that needs to be urgently solved in the industry. Summary of the Invention

[0004] In view of the above problems existing in the prior art, an embodiment of the present invention provides a ground vertical track slope inversion method and device based on a spaceborne photon counting radar.

[0005] In a first aspect, an embodiment of the present invention provides a ground vertical track slope inversion method based on a spaceborne photon counting radar, comprising:

[0006] Input the system parameters of the spaceborne photon counting radar, vertical track slope inversion control parameters and single track point cloud data;

[0007] The system parameters of the spaceborne photon counting radar include: the root mean square pulse width of the transmitted laser pulse, the laser pointing angle, the root mean square radius of the laser footprint, the photon detector dead zone time, and the number of photon detector channels; the vertical track slope inversion control parameters include: the length of the along-track segment and the interval of the elevation segment; the single-track point cloud data includes: photon classification identification, point cloud along-track distance and elevation, point cloud total along-track length, point cloud along-track resolution, and noise rate;

[0008] Calculate the along-track slope and roughness of the ground;

[0009] The calculation of the ground slope and roughness along the track includes: dividing the single track point cloud data into M equal parts along the track direction. s Along-track segments:

[0010]

[0011] Where L represents the total length of the single-track point cloud data along the track, ΔL represents the length of the segment along the track, and fix represents the rounding operation towards zero.

[0012] Selecting point cloud data identified as ground by photon classification, and calculating the along-track slope and roughness of the ground in each along-track segment;

[0013] Accumulating point cloud data to generate a photon histogram;

[0014] Restore the photon histogram to the ground reflection signal;

[0015] Extract the RMS pulse width of the ground reflection signal;

[0016] The step of extracting the root mean square pulse width of the ground reflection signal includes:

[0017] The nonlinear fitting algorithm and Gaussian model are used to calculate the ground reflection signal Sg ijp Perform fitting to obtain the best Gaussian fitting function Sf ijp :

[0018]

[0019] Where A ij Represents the best Gaussian fitting function Sf ijp The amplitude, B ij Indicates the elevation center of the single-track point cloud data, C ij Indicates the root mean square width of the ground reflection signal; E ijp represents the elevation value of the pth layer, the subscript i represents the number of the along-track segment, and the subscript j represents the number of the laser footprint in each along-track segment;

[0020] Extract the root mean square pulse width δp of the ground reflection signal ij :

[0021] δp ij =2C ij / c;

[0022] Where, δp ij is the RMS pulse width of the ground-reflected signal, and c is the speed of light in vacuum;

[0023] Calculate the ground vertical track slope;

[0024] The calculating of the ground vertical track slope includes:

[0025] Calculate the ground vertical track slope sc within the laser footprint of each track segment ij :

[0026]

[0027] Where, is the laser pointing angle, d is the root mean square radius of the laser footprint, δf is the root mean square pulse width of the emitted laser pulse, r ij is the ground roughness within the laser footprint for each track segment, sa ij is the ground along-track slope within the laser footprint of each along-track segment;

[0028] Calculate the vertical track slope sc of the ground within the laser footprint of each track segment ij The mean of the ground vertical track slope ps corresponding to each track segment is obtained i :

[0029]

[0030] Where M f is the total number of laser footprints.

[0031] Based on the content of the above method embodiment, the ground vertical track slope inversion method based on spaceborne photon counting radar provided in the embodiment of the present invention is:

[0032] The step of selecting point cloud data identified as ground by photon classification and calculating the along-track slope and roughness of the ground in each along-track segment includes:

[0033] The point cloud distance l along the track in each segment along the track ij The point cloud data within the laser footprint range is selected as the center of the laser footprint (x ijk ,H ijk ); where x ijk and H ijkrepresent the along-track distance and elevation of the kth ground point cloud data within the jth laser footprint in the i-th along-track segment, respectively. ijk ∈[l ij -2d,l ij +2d], d is the root mean square radius of the laser footprint; subscript i = 1, 2, ... M s Indicates the sequence number of the segment along the track, subscript j = 1, 2, ... M f Indicates the laser footprint number in each track segment, M f =fix(ΔL / Δl) is the total number of corresponding laser footprints, Δl is the point cloud along-track resolution, subscript k = 1, 2, ... N ij Indicates the serial number of the ground point cloud data within the laser footprint range, N ij is the total number of corresponding point cloud data;

[0034] The linear fitting method is used to perform linear fitting on the ground point cloud data within the laser footprint range of each track segment to obtain the best fitting straight line equation y ijk :

[0035] yi jk =ai j xi jk +bi j

[0036] Among them, a ij and b ij They represent the coefficient term and constant term of the best fitting straight line respectively;

[0037] Calculate the ground along-track slope sa within the laser footprint of each along-track segment ij :

[0038] sa ij =tan -1 (a ij )

[0039] Calculate the ground roughness r within the laser footprint of each track segment ij :

[0040]

[0041] Based on the content of the above method embodiment, the ground vertical track slope inversion method based on spaceborne photon counting radar provided in the embodiment of the present invention, the accumulated point cloud data generates a photon histogram, including: according to the elevation slice interval Δh, the elevation data H within the laser footprint range of each along-track segment is converted into ijk Divide the height to get the elevation value E of each layer ijp :

[0042] E ijp =Hminij +(p-1)Δh

[0043] Among them, Hmin ij is the elevation data H within the jth laser footprint in the i-th track segment ijk (k=1,2,…N ij ), p represents the number of layers of elevation data, p=1,2,…D ij , where D ij Represents the total number of layers of elevation data:

[0044]

[0045] Among them, Hmax ij is the elevation data H within the jth laser footprint in the i-th track segment ijk (k=1,2,…N ij )'s maximum value;

[0046] Statistical analysis of the two adjacent elevation slices [E ijp ,E ijp+1 ] point cloud number, generate photon histogram Hist ijp :

[0047] Hist ijp =length(H ijk ≥E ijp &H ijk <E ijp+1 )

[0048] Among them, length represents the total number of point clouds in the elevation layer, and the photon histogram Hist ijp The subscript p in the photon histogram Hist ijp The interval number, p = 1, 2, ... D ij -1;

[0049] The distance along the track l ij As the center, ij -2d,l ij +2d] range of photon histogram Hist ijp Assign Gaussian weights and accumulate to generate a new photon histogram NHist ijp :

[0050]

[0051] Among them, u represents [l ij -2d,l ij +2d] within the laser footprint serial number, j d=fix[2d / Δl] represents the total number of laser footprints within the 2d range, and max and min represent the maximum and minimum value operations.

[0052] On the basis of the content of the above method embodiment, the ground vertical track slope inversion method based on spaceborne photon counting radar provided in the embodiment of the present invention, wherein the photon histogram is restored to the ground reflection signal, comprises: calculating [E ijp ,E ijp+1 ]Detection probability Pb of point cloud ijp :

[0053]

[0054] Where n is the number of photon detector channels;

[0055] The detection probability Pb ijp Restored to ground reflection signal Sg ijp :

[0056]

[0057] Where τ = 2Δh / c represents the time resolution corresponding to the elevation slice interval Δh, c is the speed of light in vacuum, and f ij is the noise rate of the point cloud data within the laser footprint of each track segment, t d is the dead zone duration of the photon detector, the subscript m represents the interval number of the ground reflection signal, and ceil represents the rounding operation towards positive infinity.

[0058] In the second aspect, an embodiment of the present invention provides a ground vertical track slope inversion device based on a space-borne photon counting radar, comprising: a first main module for inputting system parameters, vertical track slope inversion control parameters and single-track point cloud data of the space-borne photon counting radar; a second main module for calculating the along-track slope and roughness of the ground; a third main module for accumulating point cloud data to generate a photon histogram; a fourth main module for restoring the photon histogram to a ground reflection signal; a fifth main module for extracting the root mean square pulse width of the ground reflection signal; a sixth main module for solving the ground vertical track slope; the ground vertical track slope inversion device based on a space-borne photon counting radar is used to execute the ground vertical track slope inversion method based on a space-borne photon counting radar provided by any one of the various implementation methods of the first aspect.

[0059] In a third aspect, an embodiment of the present invention provides an electronic device, including:

[0060] at least one processor; and

[0061] at least one memory in communication with the processor, wherein:

[0062] The memory stores program instructions that can be executed by the processor. The processor calls the program instructions to execute the ground vertical track slope inversion method based on space-borne photon counting radar provided by any one of the various implementation methods of the first aspect.

[0063] In a fourth aspect, an embodiment of the present invention provides a non-transitory computer-readable storage medium, which stores computer instructions, and the computer instructions enable a computer to execute the ground vertical track slope inversion method based on spaceborne photon counting radar provided by any one of the various implementation methods of the first aspect.

[0064] The embodiments of the present invention provide a method and device for inverting the ground vertical track slope based on a spaceborne photon counting radar. The method and device can invert the ground vertical track slope based on the single-track point cloud data of the spaceborne photon counting radar. The method is applicable to single-beam and multi-beam spaceborne photon counting radars, greatly improving the resolution of the ground vertical track slope inversion and enhancing the robustness of the ground vertical track slope inversion accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0066] Figure 1 A flow chart of a method for ground vertical track slope inversion based on a spaceborne photon counting radar provided in an embodiment of the present invention;

[0067] Figure 2 A schematic structural diagram of a ground vertical track slope inversion device based on a spaceborne photon counting radar provided in an embodiment of the present invention;

[0068] Figure 3 A schematic diagram of the physical structure of an electronic device provided in an embodiment of the present invention;

[0069] Figure 4 A schematic diagram of the distribution effect of single-track point cloud data provided by an embodiment of the present invention;

[0070] Figure 5 A schematic diagram of the point cloud noise rate distribution effect provided by an embodiment of the present invention;

[0071] Figure 6 A schematic diagram of the straight line fitting equation and along-track slope and roughness results for the ground point cloud data within the first laser footprint of the first along-track segment provided in an embodiment of the present invention;

[0072] Figure 7 A schematic diagram of the distribution of ground reflection signals obtained by restoring the photon histogram of ground point cloud data within the first laser footprint of the first along-track segment provided by an embodiment of the present invention;

[0073] Figure 8 A schematic diagram of the distribution of ground reflection signals obtained by restoring the photon histogram of ground point cloud data within the first laser footprint of the first along-track segment provided by an embodiment of the present invention;

[0074] Figure 9 A schematic diagram of Gaussian fitting results of a ground reflection signal within the first laser footprint of the first along-track segment provided by an embodiment of the present invention;

[0075] Figure 10 A schematic diagram of the difference distribution between the ground vertical track slope extraction result and the reference result provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0076] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. In addition, the technical features in the various embodiments or single embodiments provided by the present invention can be arbitrarily combined with each other to form a feasible technical solution. This combination is not restricted by the sequence of steps and / or structural composition mode, but must be based on the ability of ordinary technicians in this field to implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0077] The embodiment of the present invention provides a ground vertical track slope inversion method based on spaceborne photon counting radar, see Figure 1 The method includes: inputting system parameters of a spaceborne photon counting radar, vertical track slope inversion control parameters, and single-track point cloud data; calculating the along-track slope and roughness of the ground; accumulating the point cloud data to generate a photon histogram; restoring the photon histogram into a ground reflection signal; extracting the root mean square pulse width of the ground reflection signal; and solving the ground vertical track slope.

[0078] Based on the content of the above method embodiment, as an optional embodiment, the ground vertical track slope inversion method based on space-borne photon counting radar is provided in the embodiment of the present invention, and the system parameters of the space-borne photon counting radar include: the root mean square pulse width of the emitted laser pulse, the laser pointing angle, the root mean square radius of the laser footprint, the photon detector dead time and the number of photon detector channels; the vertical track slope inversion control parameters include: along-track segment length and elevation segment interval; the single-track point cloud data includes: photon classification identification, point cloud along-track distance and elevation, point cloud total along-track length, point cloud along-track resolution and noise rate.

[0079] Based on the content of the above method embodiment, as an optional embodiment, the ground vertical track slope inversion method based on space-borne photon counting radar provided in the embodiment of the present invention, the calculation of the ground along-track slope and roughness includes: dividing the single-track point cloud data into M equal parts in the along-track direction s Along-track segments:

[0080]

[0081] Where L represents the total length of the single-track point cloud data along the track, ΔL represents the length of the segment along the track, and fix represents the rounding operation towards zero;

[0082] Select point cloud data identified as ground by photon classification and calculate the along-track slope and roughness of the ground in each along-track segment, including:

[0083] The point cloud distance l along the track in each segment along the track ij The point cloud data within the laser footprint range is selected as the center of the laser footprint. ijk ,H ijk ); where x ijk and H ijk represent the along-track distance and elevation of the kth ground point cloud data within the jth laser footprint in the i-th along-track segment, respectively. ijk ∈[l ij -2d,l ij +2d], d is the root mean square radius of the laser footprint; subscript i = 1, 2, ... M s Indicates the sequence number of the segment along the track, subscript j = 1, 2, ... M f Indicates the laser footprint number in each track segment, M f =fix(ΔL / Δl) is the total number of corresponding laser footprints, Δl is the point cloud along-track resolution, subscript k = 1, 2, ... N ij Indicates the serial number of the ground point cloud data within the laser footprint range, N ij is the total number of corresponding point cloud data;

[0084] The linear fitting method is used to perform linear fitting on the ground point cloud data within the laser footprint range of each track segment to obtain the best fitting straight line equation y ijk :

[0085] yi jk =ai j xi jk +bi j

[0086] Among them, a ij and b ij They represent the coefficient term and constant term of the best fitting straight line respectively;

[0087] Calculate the ground along-track slope sa within the laser footprint of each along-track segment ij :

[0088] sa ij =tan -1 (a ij )

[0089] Calculate the ground roughness r within the laser footprint of each track segment ij :

[0090]

[0091] Based on the content of the above method embodiment, as an optional embodiment, the ground vertical track slope inversion method based on space-borne photon counting radar provided in the embodiment of the present invention, the accumulated point cloud data generates a photon histogram, including: according to the elevation slice interval Δh, the elevation data H within the laser footprint range of each along-track segment is converted into ijk Divide the height to get the elevation value E of each layer ijp :

[0092] E ijp =Hmin ij +(p-1)Δh

[0093] Among them, Hmin ij is the elevation data H within the jth laser footprint in the i-th track segment ijk (k=1,2,…N ij ), p represents the number of layers of elevation data, p=1,2,…D ij , where D ij Represents the total number of layers of elevation data:

[0094]

[0095] Among them, Hmax ij is the elevation data H within the jth laser footprint in the i-th track segment ijk(k=1,2,…N ij )'s maximum value;

[0096] Statistical analysis of the two adjacent elevation slices [E ijp ,E ijp+1 ] point cloud number, generate photon histogram Hist ijp :

[0097] Hist ijp =length(H ijk ≥E ijp &H ijk <E ijp+1 )

[0098] Among them, length represents the total number of point clouds in the elevation layer, and the photon histogram Hist ijp The subscript p in the photon histogram Hist ijp The interval number, p = 1, 2, ... D ij -1;

[0099] The distance along the track l ij As the center, ij -2d,l ij +2d] range of photon histogram Hist ijp Assign Gaussian weights and accumulate to generate a new photon histogram NHist ijp :

[0100]

[0101] Among them, u represents [l ij -2d,l ij +2d] within the laser footprint serial number, j d =fix[2d / Δl] represents the total number of laser footprints within the 2d range, and max and min represent the maximum and minimum value operations.

[0102] Based on the content of the above method embodiment, as an optional embodiment, the ground vertical track slope inversion method based on space-borne photon counting radar provided in the embodiment of the present invention, wherein the photon histogram is restored to the ground reflection signal, comprises: calculating [E ijp ,E ijp+1 ]Detection probability Pb of point cloud ijp :

[0103]

[0104] Where n is the number of photon detector channels;

[0105] The detection probability Pb ijpRestored to ground reflection signal Sg ijp :

[0106]

[0107] Where τ = 2Δh / c represents the time resolution corresponding to the elevation slice interval Δh, c is the speed of light in vacuum, and f ij is the noise rate of the point cloud data within the laser footprint of each track segment, t d is the dead zone duration of the photon detector, the subscript m represents the interval number of the ground reflection signal, and ceil represents the rounding operation towards positive infinity.

[0108] Based on the content of the above method embodiment, as an optional embodiment, the ground vertical track slope inversion method based on spaceborne photon counting radar provided in the embodiment of the present invention, wherein the extracting the root mean square pulse width of the ground reflection signal includes:

[0109] The nonlinear fitting algorithm and Gaussian model are used to calculate the ground reflection signal Sg ijp Perform fitting to obtain the best Gaussian fitting function Sf ijp :

[0110]

[0111] Among them, A ij Represents the best Gaussian fitting function Sf ijp The amplitude, B ij Indicates the elevation center of the single-track point cloud data, C ij Indicates the root mean square width of the ground reflection signal; E ijp represents the elevation value of the pth layer, the subscript i represents the number of the along-track segment, and the subscript j represents the number of the laser footprint in each along-track segment;

[0112] Extract the root mean square pulse width δp of the ground reflection signal ij :

[0113] δp ij =2C ij / c

[0114] Where, δp ij is the RMS pulse width of the signal reflected from the ground, and c is the speed of light in a vacuum.

[0115] Based on the content of the above method embodiment, as an optional embodiment, the ground vertical track slope inversion method based on spaceborne photon counting radar provided in the embodiment of the present invention includes:

[0116] Calculate the ground vertical track slope sc within the laser footprint of each track segment ij :

[0117]

[0118] in, is the laser pointing angle, d is the root mean square radius of the laser footprint, δf is the root mean square pulse width of the emitted laser pulse, r ij is the ground roughness within the laser footprint for each track segment, sa ij is the ground along-track slope within the laser footprint of each along-track segment;

[0119] Calculate the vertical track slope sc of the ground within the laser footprint of each track segment ij The mean of the ground vertical track slope ps corresponding to each track segment is obtained i :

[0120]

[0121] Where M f is the total number of laser footprints.

[0122] The ground vertical track slope inversion method based on spaceborne photon counting radar provided in an embodiment of the present invention can invert the ground vertical track slope based on the single-track point cloud data of the spaceborne photon counting radar. It is applicable to single-beam and multi-beam spaceborne photon counting radars, greatly improving the resolution of ground vertical track slope inversion and enhancing the robustness of the ground vertical track slope inversion accuracy.

[0123] In another embodiment, a ground vertical track slope inversion method based on a spaceborne photon counting radar includes: Step 1, inputting system parameters of the spaceborne photon counting radar, vertical track slope inversion control parameters, and single track point cloud data, mainly including:

[0124] System parameters of spaceborne photon counting radar: RMS pulse width of transmitted laser pulse δf = 0.64ns, laser pointing angle Laser footprint root mean square radius d = 2.75m, photon detector dead time t d =3.2ns, number of photon detector channels n=16.

[0125] Vertical track slope inversion control parameters: along-track segment length ΔL = 98 m, elevation slice interval Δh = 0.1 m.

[0126] Single track point cloud data: The third strong laser beam track of the advanced terrain lidar passing through a place is selected, and its point cloud data is downloaded from a center. Photon classification identification, point cloud distance along the track and elevation distribution are shown in Figure 4 As shown (the distance from the starting point of the point cloud along the track is set to 0 for easy display), the total length of the point cloud along the track is L = 10682m, the resolution of the point cloud along the track is Δl = 0.7m, and the noise rate f within the laser footprint of each along-track segment is ijare the same, and their distribution is as follows Figure 5 shown.

[0127] Step 2, calculating the ground slope and roughness along the track, includes the following sub-steps:

[0128] Step 2.1: Divide the single-track point cloud data into M equal parts along the track direction. s Along-track segments:

[0129]

[0130] Step 2.2, select the point cloud data identified as ground by photon classification, and calculate the along-track slope and roughness of the ground in each along-track segment, including the following sub-processes:

[0131] (2.2.1) Take the distance l along the track of all point clouds in each along-track segment ij The point cloud data within the laser footprint range is selected as the center of the laser footprint. ijk ,H ijk ). Where x ijk and H ijk represent the along-track distance and elevation of the kth ground point cloud data within the jth laser footprint in the i-th along-track segment, respectively. ijk ∈[l ij -5.5,l ij +5.5], subscript i = 1, 2, ... 109 represents the number of the along-track segment, subscript j = 1, 2, ... 140 represents the number of the laser footprint in each along-track segment, subscript k = 1, 2, ... N ij Indicates the sequence number of the ground point cloud data within the laser footprint of each track segment, N ij is the total number of corresponding point cloud data.

[0132] (2.2.2) Use the linear fitting method to perform a straight line fitting on the ground point cloud data within the laser footprint of each track segment to obtain the best fitting straight line equation y ijk :

[0133] y ijk =a ij x ijk +b ij

[0134] Where a ij and b ij They represent the coefficient term and constant term of the best fitting straight line respectively.

[0135] (2.2.3) Calculate the ground slope sa within the laser footprint of each track segment ij :

[0136] sa ij=arctan(a ij )

[0137] (2.2.4) Calculate the ground roughness r within the laser footprint of each track segment ij :

[0138]

[0139] Figure 6 The straight line fitting equation of the ground point cloud data within the first laser footprint of the first along-track segment and the along-track slope and roughness results are shown.

[0140] Step 3, accumulating point cloud data to generate a photon histogram, includes the following sub-steps:

[0141] Step 3.1: At an interval of 0.1 m, the elevation data H within the laser footprint of each track segment is recorded. ijk Divide the height to get the elevation value E of each layer ijp :

[0142] E ijp =Hmin ij +0.1(p-1)

[0143] Where Hmin ij is the elevation data H within the jth laser footprint in the i-th track segment ijk (k=1,2,…N ij ), p represents the number of layers of elevation data, p=1,2,…D ij , where D ij Represents the total number of layers of elevation data:

[0144]

[0145] Where Hmax ij is the elevation data H within the jth laser footprint in the i-th track segment ijk (k=1,2,…N ij ) is the maximum value of .

[0146] Step 3.2: Count the [E ijp ,E ijp+1 ] point cloud number, generate photon histogram Hist ijp :

[0147] Hist ijp =length(H ijk ≥E ijp &H ijk <E ijp+1 )

[0148] Where, length represents the total number of point clouds in the elevation slice, and the photon histogram Hist ijp The subscript p in the photon histogram Hist ijp The interval number, p = 1, 2, ... D ij -1.

[0149] Step 3.3, take the distance along the track l ij As the center, ij -5.5,l ij Photon histogram Hist in the range of +5.5] ijp Assign Gaussian weights and accumulate to generate a new photon histogram NHist ijp :

[0150]

[0151] Where, u represents [l ij -5.5,l ij +5.5], max and min represent the maximum and minimum value operations.

[0152] Figure 7 Shown is the photon histogram of the ground point cloud data within the first laser footprint of the first along-track segment.

[0153] Step 4, restoring the photon histogram to the ground reflection signal, includes the following sub-steps:

[0154] Step 4.1, calculate the [E ijp ,E ijp+1 ]Detection probability Pb of point cloud ijp :

[0155]

[0156] Step 4.2: Set the detection probability Pb ijp Restored to ground reflection signal Sg ijp :

[0157]

[0158] Where, τ = 0.67ns represents the time resolution corresponding to the elevation slice interval, f ij is the noise rate of the corresponding point cloud data within the laser footprint of each track segment, t d =3.2ns is the dead time of the photon detector, and the subscript m represents the interval number of the ground reflection signal.

[0159] Figure 8The distribution of ground reflection signals obtained by restoring the photon histogram of the ground point cloud data within the first laser footprint of the first along-track segment is shown.

[0160] Step 5, extracting the root mean square pulse width of the ground reflection signal, includes the following sub-steps:

[0161] Step 5.1: Use nonlinear fitting algorithm and Gaussian model to calculate the ground reflection signal Sg ijp Perform fitting to obtain the best Gaussian fitting function Sf ijp :

[0162]

[0163] Where A ij Represents the best Gaussian fitting function Sf ijp The amplitude, B ij Indicates the elevation center of the single-track point cloud data, C ij Indicates the RMS width of the ground reflection signal.

[0164] Step 5.2, extract the root mean square pulse width δp of the ground reflection signal ij :δp ij =2C ij / (3×10 8 ).

[0165] Figure 9 The Gaussian fitting results of the ground reflection signal within the first laser footprint of the first along-track segment are shown.

[0166] Step 6, calculating the ground vertical track slope, includes the following sub-steps:

[0167] Step 6.1, calculate the ground vertical track slope sc within the laser footprint of each track segment ij :

[0168]

[0169] Step 6.2: Calculate the vertical track slope sc within the laser footprint of each track segment. ij The mean of the ground vertical track slope ps corresponding to each track segment is obtained i :

[0170]

[0171] This embodiment extracts the ground vertical track slope of 109 along-track segments. The airborne lidar data within each along-track segment (98m along the track × 11m vertical track) is selected as the ground reference data source. The plane fitting method is used to perform plane fitting on the ground reference data within each along-track segment, and the absolute value of the arc tangent of the slope of the fitting plane in the vertical track direction is calculated as the reference value of the ground vertical track slope. By comparing the difference between the extracted ground vertical track slope and the reference value, the correctness of the ground vertical track slope inversion method based on spaceborne photon counting radar point cloud data is evaluated.

[0172] Figure 10 A distribution diagram of the differences between the ground vertical track slope extraction results and the reference results is presented. Approximately 77% of the ground vertical track slope differences have an absolute value of no more than 2°. Statistical analysis reveals that the mean and standard deviation of 109 ground vertical track slope differences are 0.88° and 1.81°, respectively. Furthermore, the 11m inversion resolution of the vertical track slope in the vertical direction is significantly smaller than the 90m vertical track spacing between the strong and weak beams, demonstrating that the ground vertical track slope inversion method proposed in this paper has high inversion accuracy and resolution.

[0173] The implementation basis of each embodiment of the present invention is to implement programmed processing through a device with processor functions. Therefore, in engineering practice, the technical solutions and functions of each embodiment of the present invention can be encapsulated into various modules. Based on this reality, on the basis of the above embodiments, an embodiment of the present invention provides a ground vertical track slope inversion device based on a space-borne photon counting radar, which is used to execute the ground vertical track slope inversion method based on a space-borne photon counting radar in the above method embodiment. Figure 2 The device includes: a first main module, used to input system parameters of the space-borne photon counting radar, vertical track slope inversion control parameters and single-track point cloud data; a second main module, used to calculate the along-track slope and roughness of the ground; a third main module, used to accumulate point cloud data to generate a photon histogram; a fourth main module, used to restore the photon histogram to a ground reflection signal; a fifth main module, used to extract the root mean square pulse width of the ground reflection signal; and a sixth main module, used to solve the ground vertical track slope.

[0174] The ground vertical track slope inversion device based on spaceborne photon counting radar provided by the embodiment of the present invention adopts Figure 2 Several modules in the system can invert the ground vertical track slope based on the single-track point cloud data of spaceborne photon counting radar. It is applicable to single-beam and multi-beam spaceborne photon counting radars, greatly improving the resolution of ground vertical track slope inversion and enhancing the robustness of ground vertical track slope inversion accuracy.

[0175] It should be noted that the device in the device embodiment provided by the present invention can be used to implement the method in the above-mentioned method embodiment as well as the method in other method embodiments provided by the present invention. The only difference is that the corresponding functional modules are set. The principle is basically the same as the principle of the above-mentioned device embodiment provided by the present invention. As long as those skilled in the art refer to the specific technical solutions in other method embodiments on the basis of the above-mentioned device embodiment, obtain the corresponding technical means and the technical solutions composed of these technical means by combining technical features, and ensure the practicality of the technical solutions, they can improve the device in the above-mentioned device embodiment to obtain the corresponding device class embodiment, thereby obtaining the corresponding device class embodiment for implementing the methods in other method class embodiments. For example:

[0176] Based on the content of the above-mentioned device embodiment, as an optional embodiment, the ground vertical track slope inversion device based on space-borne photon counting radar provided in the embodiment of the present invention also includes: a first submodule, used to realize the system parameters of the space-borne photon counting radar, vertical track slope inversion control parameters and single-track point cloud data, including: system parameters of the space-borne photon counting radar: root mean square pulse width of the emitted laser pulse, laser pointing angle, root mean square radius of the laser footprint, photon detector dead time, number of photon detector channels; vertical track slope inversion control parameters: along-track segment length, elevation segment interval; single-track point cloud data: photon classification identifier, point cloud along-track distance and elevation, point cloud total along-track length, point cloud along-track resolution, and noise rate.

[0177] Based on the content of the above device embodiment, as an optional embodiment, the ground vertical track slope inversion device based on space-borne photon counting radar provided in the embodiment of the present invention further includes: a second submodule for realizing the calculation of the ground along-track slope and roughness, including: dividing the single-track point cloud data into M equal parts in the along-track direction; s Along-track segments:

[0178]

[0179] Where L represents the total length of the single-track point cloud data along the track, ΔL represents the length of the segment along the track, and fix represents the rounding operation towards zero;

[0180] Select point cloud data identified as ground by photon classification and calculate the along-track slope and roughness of the ground in each along-track segment, including:

[0181] The point cloud distance l along the track in each segment along the track ij The point cloud data within the laser footprint range is selected as the center of the laser footprint. ijk ,H ijk ); where x ijk and H ijkrepresent the along-track distance and elevation of the kth ground point cloud data within the jth laser footprint in the i-th along-track segment, respectively. ijk ∈[l ij -2d,l ij +2d], d is the root mean square radius of the laser footprint; subscript i = 1, 2, ... M s Indicates the sequence number of the segment along the track, subscript j = 1, 2, ... M f Indicates the laser footprint number in each track segment, M f =fix(ΔL / Δl) is the total number of corresponding laser footprints, Δl is the point cloud along-track resolution, subscript k = 1, 2, ... N ij Indicates the serial number of the ground point cloud data within the laser footprint range, N ij is the total number of corresponding point cloud data;

[0182] The linear fitting method is used to perform linear fitting on the ground point cloud data within the laser footprint range of each track segment to obtain the best fitting straight line equation y ijk :

[0183] yi jk =ai j xi jk +bi j

[0184] Among them, a ij and b ij They represent the coefficient term and constant term of the best fitting straight line respectively;

[0185] Calculate the ground along-track slope sa within the laser footprint of each along-track segment ij :

[0186] sa ij =tan -1 (a ij )

[0187] Calculate the ground roughness r within the laser footprint of each track segment ij :

[0188]

[0189] Based on the content of the above-mentioned device embodiment, as an optional embodiment, the ground vertical track slope inversion device based on space-borne photon counting radar provided in the embodiment of the present invention further includes: a third submodule for realizing the generation of a photon histogram from the accumulated point cloud data, including: accumulating the elevation data H within the laser footprint range of each along-track segment according to the elevation slice interval Δh; ijk Divide the height to get the elevation value E of each layer ijp :

[0190] Eijp =Hmin ij +(p-1)Δh

[0191] Among them, Hmin ij is the elevation data H within the jth laser footprint in the i-th track segment ijk (k=1,2,…N ij ), p represents the number of layers of elevation data, p=1,2,…D ij , where D ij Represents the total number of layers of elevation data:

[0192]

[0193] Among them, Hmax ij is the elevation data H within the jth laser footprint in the i-th track segment ijk (k=1,2,…N ij )'s maximum value;

[0194] Statistical analysis of the two adjacent elevation slices [E ijp ,E ijp+1 ] point cloud number, generate photon histogram Hist ijp :

[0195] Hist ijp =length(H ijk ≥E ijp &H ijk <E ijp+1 )

[0196] Among them, length represents the total number of point clouds in the elevation layer, and the photon histogram Hist ijp The subscript p in the photon histogram Hist ijp The interval number, p = 1, 2, ... D ij -1;

[0197] The distance along the track l ij As the center, ij -2d,l ij +2d] range of photon histogram Hist ijp Assign Gaussian weights and accumulate to generate a new photon histogram NHist ijp :

[0198]

[0199] Among them, u represents [l ij -2d,l ij +2d] within the laser footprint serial number, j d=fix[2d / Δl] represents the total number of laser footprints within the 2d range, and max and min represent the maximum and minimum value operations.

[0200] Based on the content of the above device embodiment, as an optional embodiment, the ground vertical track slope inversion device based on space-borne photon counting radar provided in the embodiment of the present invention further includes: a fourth submodule for realizing the restoration of the photon histogram into the ground reflection signal, including: calculating the [E ijp ,E ijp+1 ]Detection probability Pb of point cloud ijp :

[0201]

[0202] Where n is the number of photon detector channels;

[0203] The detection probability Pb ijp Restored to ground reflection signal Sg ijp :

[0204]

[0205] Where τ = 2Δh / c represents the time resolution corresponding to the elevation slice interval Δh, c is the speed of light in vacuum, and f ij is the noise rate of the point cloud data within the laser footprint of each track segment, t d is the dead zone duration of the photon detector, the subscript m represents the interval number of the ground reflection signal, and ceil represents the rounding operation towards positive infinity.

[0206] Based on the content of the above device embodiment, as an optional embodiment, the ground vertical track slope inversion device based on space-borne photon counting radar provided in the embodiment of the present invention further includes: a fifth submodule for realizing the extraction of the root mean square pulse width of the ground reflection signal, including:

[0207] The nonlinear fitting algorithm and Gaussian model are used to calculate the ground reflection signal Sg ijp Perform fitting to obtain the best Gaussian fitting function Sf ijp :

[0208]

[0209] Among them, A ij Represents the best Gaussian fitting function Sf ijp The amplitude, B ij Indicates the elevation center of the single-track point cloud data, C ij Indicates the root mean square width of the ground reflection signal; E ijprepresents the elevation value of the pth layer, the subscript i represents the number of the along-track segment, and the subscript j represents the number of the laser footprint in each along-track segment;

[0210] Extract the root mean square pulse width δp of the ground reflection signal ij :

[0211] δp ij =2C ij / c

[0212] Where, δp ij is the RMS pulse width of the signal reflected from the ground, and c is the speed of light in a vacuum.

[0213] Based on the content of the above device embodiment, as an optional embodiment, the ground vertical track slope inversion device based on space-borne photon counting radar provided in the embodiment of the present invention further includes: a sixth submodule for implementing the solution of the ground vertical track slope, including:

[0214] Calculate the ground vertical track slope sc within the laser footprint of each track segment ij :

[0215]

[0216] in, is the laser pointing angle, d is the laser footprint root mean square radius, δf is the root mean square pulse width of the emitted laser pulse; r ij is the ground roughness within the laser footprint for each track segment, sa ij is the ground along-track slope within the laser footprint of each along-track segment;

[0217] Calculate the vertical track slope sc of the ground within the laser footprint of each track segment ij The mean of the ground vertical track slope ps corresponding to each track segment is obtained i :

[0218]

[0219] Where M f is the total number of laser footprints.

[0220] The method of the embodiment of the present invention is implemented by electronic devices, so it is necessary to introduce the relevant electronic devices. Based on this purpose, the embodiment of the present invention provides an electronic device, such as Figure 3As shown, the electronic device includes: at least one processor, a communications interface, at least one memory, and a communications bus, wherein the at least one processor, the communications interface, and the at least one memory communicate with each other via the communications bus. The at least one processor can call logic instructions in the at least one memory to execute all or part of the steps of the methods provided in the aforementioned method embodiments.

[0221] In addition, the logic instructions in the at least one memory mentioned above can be implemented in the form of a software functional unit and can be stored in a computer-readable storage medium when sold or used as an independent product. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in each method embodiment of the present invention. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0222] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, i.e., they may be located in one location or distributed across multiple network units. Some or all of the modules may be selected based on actual needs to achieve the objectives of the present embodiment. Persons of ordinary skill in the art will be able to understand and implement the present invention without inventive effort.

[0223] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform, and of course can also be implemented by hardware. Based on this understanding, the essence of the above technical solution or the part that contributes to the existing technology can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a magnetic disk, an optical disk, etc., and includes a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiment.

[0224] The flowcharts and block diagrams in the accompanying drawings show the possible architectures, functions and operations of the systems, methods and computer program products according to multiple embodiments of the present invention. Based on this understanding, each box in the flowchart or block diagram can represent a module, program segment or part of the code, and the module, program segment or part of the code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in an order different from that marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, or sometimes in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or flowchart, and the combination of boxes in the block diagram and / or flowchart, can be implemented with a dedicated hardware-based system that performs the specified function or action, or can be implemented with a combination of dedicated hardware and computer instructions.

[0225] It should be noted that the terms "comprise," "include," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, the elements defined by the phrase "comprise..." do not preclude the presence of additional identical elements in the process, method, article, or apparatus comprising the elements.

[0226] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A ground vertical track slope inversion method based on spaceborne photon counting radar, characterized in that: include: Input the system parameters of the spaceborne photon counting radar, vertical track slope inversion control parameters and single track point cloud data; The system parameters of the spaceborne photon counting radar include: the root mean square pulse width of the transmitted laser pulse, the laser pointing angle, the root mean square radius of the laser footprint, the photon detector dead zone time, and the number of photon detector channels; the vertical track slope inversion control parameters include: the length of the along-track segment and the interval of the elevation segment; the single-track point cloud data includes: photon classification identification, point cloud along-track distance and elevation, point cloud total along-track length, point cloud along-track resolution, and noise rate; Calculate the along-track slope and roughness of the ground; The calculation of the ground slope and roughness along the track includes: dividing the single track point cloud data into M equal parts along the track direction. s Along-track segments: Where L represents the total length of the single-track point cloud data along the track, ΔL represents the length of the segment along the track, and fix represents the rounding operation towards zero. Selecting point cloud data identified as ground by photon classification, and calculating the along-track slope and roughness of the ground in each along-track segment; Accumulating point cloud data to generate a photon histogram; Restore the photon histogram to the ground reflection signal; Extract the RMS pulse width of the ground reflection signal; The step of extracting the root mean square pulse width of the ground reflection signal includes: The nonlinear fitting algorithm and Gaussian model are used to calculate the ground reflection signal Sg ijp Perform fitting to obtain the best Gaussian fitting function Sf ijp : Where A ij Represents the best Gaussian fitting function Sf ijp The amplitude, B ij Indicates the elevation center of the single-track point cloud data, C ij Indicates the root mean square width of the ground reflection signal; E ijp represents the elevation value of the pth layer, the subscript i represents the number of the along-track segment, and the subscript j represents the number of the laser footprint in each along-track segment; Extract the root mean square pulse width δp of the ground reflection signal ij : δp ij =2C ij / c; Where, δp ij is the RMS pulse width of the ground-reflected signal, and c is the speed of light in vacuum; Calculate the ground vertical track slope; The calculating of the ground vertical track slope includes: Calculate the ground vertical track slope sc within the laser footprint of each track segment ij : Where, is the laser pointing angle, d is the root mean square radius of the laser footprint, δf is the root mean square pulse width of the emitted laser pulse, r ij is the ground roughness within the laser footprint for each track segment, sa ij is the ground along-track slope within the laser footprint of each along-track segment; Calculate the vertical track slope sc of the ground within the laser footprint of each track segment ij The mean of the ground vertical track slope ps corresponding to each track segment is obtained i : Where M f is the total number of laser footprints.

2. The ground vertical track slope inversion method based on spaceborne photon counting radar according to claim 1 is characterized in that: The step of selecting point cloud data identified as ground by photon classification and calculating the along-track slope and roughness of the ground in each along-track segment includes: The point cloud distance l along the track in each segment along the track ij The point cloud data within the laser footprint range is selected as the center of the laser footprint (x ijk ,H ijk ); where x ijk and H ijk represent the along-track distance and elevation of the kth ground point cloud data within the jth laser footprint in the i-th along-track segment, respectively. ijk ∈[l ij -2d,l ij +2d], d is the root mean square radius of the laser footprint; subscript i = 1, 2, ... M s Indicates the sequence number of the segment along the track, subscript j = 1, 2, ... M f Indicates the laser footprint number in each track segment, M f =fix(ΔL / Δl) is the total number of corresponding laser footprints, Δl is the point cloud along-track resolution, subscript k = 1, 2, ... N ij Indicates the serial number of the ground point cloud data within the laser footprint range, N ij is the total number of corresponding point cloud data; The linear fitting method is used to perform linear fitting on the ground point cloud data within the laser footprint range of each track segment to obtain the best fitting straight line equation y ijk : yi jk =ai j xi jk +bi j Among them, a ij and b ij They represent the coefficient term and constant term of the best fitting straight line respectively; Calculate the ground along-track slope sa within the laser footprint of each along-track segment ij : that ij =time -1 (the ij ) Calculate the ground roughness r within the laser footprint of each track segment ij :

3. The ground vertical track slope inversion method based on spaceborne photon counting radar according to claim 2 is characterized in that: The accumulated point cloud data generates a photon histogram, including: accumulating the elevation data H within the laser footprint of each track segment according to the elevation slice interval Δh ijk Divide the height to get the elevation value E of each layer ijp : E ijp JHmin ij +(p-1)Δh Among them, Hmin ij is the elevation data H within the jth laser footprint in the i-th track segment ijk (k=1,2,…N ij ), p represents the number of layers of elevation data, p=1,2,…D ij , where D ij Represents the total number of layers of elevation data: Among them, Hmax ij is the elevation data H within the jth laser footprint in the i-th track segment ijk (k=1,2,…N ij )'s maximum value; Statistical analysis of the two adjacent elevation slices [E ijp ,E ijp+1 ] point cloud number, generate photon histogram Hist ijp : Hist ijp =length(H ijk ≥E ijp &H ijk <E ijp+1 ) Among them, length represents the total number of point clouds in the elevation layer, and the photon histogram Hist ijp The subscript p in the photon histogram Hist ijp The interval number, p = 1, 2, ... D ij -1; The distance along the track l ij As the center, ij -2d,l ij +2d] range of photon histogram Hist ijp Assign Gaussian weights and accumulate to generate a new photon histogram NHist ijp : Among them, u represents [l ij -2d,l ij +2d] within the laser footprint serial number, j d =fix[2d / Δl] represents the total number of laser footprints within the 2d range, and max and min represent the maximum and minimum value operations.

4. The ground vertical track slope inversion method based on spaceborne photon counting radar according to claim 3 is characterized in that: The method of restoring the photon histogram into the ground reflection signal includes: calculating the [E ijp ,E ijp+1 ]Detection probability Pb of point cloud ijp : Where n is the number of photon detector channels; The detection probability Pb ijp Restored to ground reflection signal Sg ijp : Where τ = 2Δh / c represents the time resolution corresponding to the elevation slice interval Δh, c is the speed of light in vacuum, and f ij is the noise rate of the point cloud data within the laser footprint of each track segment, t d is the dead zone duration of the photon detector, the subscript m represents the interval number of the ground reflection signal, and ceil represents the rounding operation towards positive infinity.

5. A ground vertical track slope inversion device based on spaceborne photon counting radar, characterized in that: include: The first main module is used to input the system parameters of the spaceborne photon counting radar, the vertical track slope inversion control parameters and the single track point cloud data; The second main module is used to calculate the along-track slope and roughness of the ground; the third main module is used to accumulate point cloud data to generate a photon histogram; the fourth main module is used to restore the photon histogram to a ground reflection signal; the fifth main module is used to extract the root mean square pulse width of the ground reflection signal; the sixth main module is used to solve the ground vertical track slope; the ground vertical track slope inversion device based on satellite-borne photon counting radar is used to execute the method described in any one of claims 1 to 4.

6. An electronic device, characterized in that: include: At least one processor, at least one memory and a communication interface; wherein, The processor, memory and communication interface communicate with each other; The memory stores program instructions that can be executed by the processor, and the processor calls the program instructions to execute the method according to any one of claims 1 to 4.

7. A non-transitory computer-readable storage medium, characterized in that The non-transitory computer-readable storage medium stores computer instructions, which cause the computer to execute the method of any one of claims 1 to 4.

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