Laser radar aerial multi-echo resolving method based on distance and reflectivity constraints

Abstract

The invention discloses a laser radar aerial multi-echo resolving method based on distance and reflectivity constraints, and the method comprises the steps: respectively building a geometric calibration equation and a radiation calibration equation of a surveying and mapping laser radar, and correcting the distance measurement indication value, the angle measurement indication value, the amplitude value and the relative reflectivity of each echo; determining the time interval of the farthest laser echo by using a time flight principle; according to the laser emission repetition frequency, the number of laser emission main waves existing in the time interval of the farthest laser echo is determined; respectively determining adjacent continuous scanning points in the pitching direction and the azimuth direction according to the scanning pitch angle and the azimuth angle; and finally, continuity judgment is carried out on the transmitted main waves, continuous noise energy is calculated based on geometric and radiation continuity between adjacent continuous scanning points by using a distance measurement result and a relative reflectivity result of each echo, a continuous noise function corresponding to each MTA is obtained, and a robust nonlinear optimization model is constructed and optimized and solved. According to the invention, accurate calculation of the MTA time can be realized.

Description

Technical Field

[0001] The invention belongs to the field of three-dimensional laser point cloud acquisition, and in particular relates to a laser radar aerial multi-echo solution method based on distance and reflectivity constraints. Background Art

[0002] Multi-Time-Around (MTA) in the air in LiDAR measurement is defined as the echo received after a time delay exceeding a multiple of a pulse repetition interval. As the effective range of surveying and mapping LiDARs becomes longer and longer and the laser emission repetition frequency becomes higher and higher, the consistency of high-density three-dimensional point clouds is a basic data quality requirement for high-precision surveying and mapping. Long distance and high repetition frequency bring about the inevitable time ambiguity problem caused by multiple echoes in the air in radar measurement, that is, within the laser flight time corresponding to the operating distance, the LiDAR has emitted multiple main waves, and there are multiple echoes in the air, resulting in time ambiguity where the echo and the main wave cannot directly correspond, resulting in the loss of consistency in the distribution of the target three-dimensional point cloud within the same scan line and between adjacent scan lines. Only by determining the emitted main wave corresponding to each echo can the laser flight time of this measurement be solved and the target distance can be accurately measured.

[0003] The MTA problem is actually a distance measurement problem of the laser radar. The laser mistakenly pulls distant points to nearby points, causing the distant point cloud to become noise in the nearby point cloud. The MTA problem will bring great difficulties to subsequent data processing, automatic target detection and recognition, map making and other process flows, leading to errors in recognition and manual processes.

[0004] Most objects in the real world, whether natural objects such as vegetation and soil or man-made objects such as roads, signs, and buildings, have surface continuity and generally do not show drastic changes in distance, texture, and reflectivity in adjacent areas.

[0005] At present, most methods for solving the time ambiguity problem of multiple echoes in the air of LiDAR are based on spatial continuity and do not take into account the inherent measurement bias of the instrument. As a result, the accuracy and robustness of LiDAR mapping that requires longer distances, higher laser emission repetition rates, and denser point clouds are affected. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention provides a method for solving multi-echo aerial laser radar based on distance and reflectivity constraints. Under the basic premise of the continuity of the scanned target surface, the inherent measurement error of the laser radar instrument itself is calibrated before solving the MTA, including:

[0007] (1) Geometric calibration: Establish a calibration model for distance and angle during LiDAR scanning measurement to improve the geometric accuracy of each measurement;

[0008] (2) Radiation calibration: Establish a calibration model for the laser radar measurement amplitude and reflectivity to improve the radiation accuracy of each measurement;

[0009] (3) The geometric and radiation continuity of the target surface is used to solve the MTA.

[0010] The purpose of the present invention is achieved through the following technical solutions:

[0011] A method for solving multi-echoes in the air of a laser radar based on distance and reflectivity constraints, the method comprising the following steps:

[0012] S1: Establish the geometric calibration equation of the surveying laser radar to correct the distance measurement indication and angle measurement indication of each echo;

[0013] S2: Establish the mapping lidar radiation calibration equation to correct the amplitude and relative reflectivity of each echo;

[0014] S3: Based on the distance measurement indication corrected by each echo of the mapping laser radar, the time interval of the farthest laser echo is determined using the time flight principle;

[0015] S4: determining the number of laser emission main waves existing in the time interval of the farthest laser echo according to the laser emission repetition frequency of the surveying and mapping laser radar;

[0016] S5: determining adjacent continuous scanning points in the pitch direction according to the scanning pitch angle; determining adjacent continuous scanning points in the azimuth direction according to the scanning azimuth angle;

[0017] S6: According to the adjacent continuous scanning points in the pitch direction and azimuth direction, the continuity of the transmitted main wave is judged. When the transmitted main wave is a continuous main wave, the continuous noise energy is calculated based on the geometric and radiation continuity between adjacent continuous scanning points using the ranging results and relative reflectivity results of each echo of the mapping laser radar. The continuity noise function corresponding to each multi-echo in the air is obtained, and a robust nonlinear optimization model is constructed and optimized to solve the multi-echo problem in the air.

[0018] Furthermore, the S1 specifically includes:

[0019] According to the distance measurement principle of surveying laser radar, referring to the distance correction technology of laser rangefinder, the laser radar distance measurement correction equation is established, and the corrected distance measurement indication R is calculated. m :

[0020] R m =R0+a R R0+b R

[0021] Where R0 is the original measured value of the distance, a R is the distance multiplication constant, b R is the distance measurement constant; by referring to the distance calibration technology of the photoelectric rangefinder, the distance indication is calibrated to obtain a R and b R ;

[0022] According to the scanning angle measurement principle of surveying laser radar, referring to the angle correction technology of theodolite and total station, the laser radar angle measurement correction equation is established, including the pitch angle correction equation and the azimuth angle correction mathematical equation, and the corrected pitch angle and azimuth angle are calculated:

[0023] θ m =θ0+a θ ·θ0+b θ

[0024] In the formula, θ m is the original measured value of the pitch angle, a θ is the pitch angle multiplied by a constant, b θ is the pitch angle constant; the pitch angle measurement indication is calibrated by referring to the pitch angle calibration technology of the photoelectric goniometer, and a is obtained θ and b θ ;

[0025]

[0026] In the formula, is the original measurement indication of azimuth, is the azimuth collimation axis correction constant, is the azimuth trunnion correction constant; the azimuth measurement indication is calibrated by referring to the azimuth calibration technology of the photoelectric goniometer, and the and

[0027] Furthermore, the S2 specifically includes:

[0028] According to the detection response principle of surveying and mapping laser radar, referring to the photoelectric sensing detection technology, the laser radar echo amplitude correction equation is established, and the corrected echo amplitude is calculated:

[0029]

[0030] Where P echo is the echo response power, P DL It is the minimum detectable power of the mapping lidar system;

[0031] According to the detection response principle of surveying and mapping laser radar, based on the relationship between the detection response amplitude of the laser detection system and the relative reflectivity, a standard diffuse reflection whiteboard that has been calibrated by metrology is used as the traceability reference of the laser radar relative reflectivity standard, and the laser radar echo relative reflectivity correction equation is established:

[0032] ρ rel =A mp_echo -A mp_ref (R m )

[0033] In the formula, A mp_echo is the echo amplitude, A mp_ref (R m ) is the reference diffuse reflection white plate at a distance R m The echo amplitude at .

[0034] Furthermore, the time interval ΔT of the farthest laser echo is max The calculation formula is as follows:

[0035]

[0036] Where c is the speed of light.

[0037] Furthermore, the calculation formula for the number N of laser emission main waves existing in the time interval of the farthest laser echo in S4 is as follows:

[0038] N=ΔT max ·PRR

[0039] Where PRR is the laser emission repetition frequency.

[0040] Furthermore, the S5 specifically includes:

[0041] By modifying the positive pitch angle measurement indication θ m Continuity judgment is performed to obtain the spatial proximity points within a scan line. If |θ m,i -θ m,i-1 |=θ m,res , then it is judged as a continuous adjacent point in the pitch direction, where θ m,res is the LiDAR elevation angle measurement resolution;

[0042] The azimuth measurement indication is corrected Perform continuity judgment to obtain spatial continuous points between adjacent scan lines. If It is judged as a continuous adjacent point in the azimuth direction, where Azimuth measurement resolution for mapping lidar.

[0043] Furthermore, the S6 specifically includes:

[0044] S6.1: Based on the number of laser emission main waves N, construct the corrected distance vector R corresponding to each possible multiple echo in the air m_MTA,j and the relative reflectivity vector ρ rel_MTA,j :

[0045] R m_MTA,j =[R m_1 R m_2 ...R m_N ]

[0046] ρ rel_MTA,j =[ρ rel_1 ρ rel_2 ... rel_N ]

[0047] Where, j corresponds to the number of multi-echoes in the air obtained by calculating S4, and j≤N;

[0048] S6.2: Construct the distance continuity noise vector ΔR respectively m_MTA,J and the relative reflectivity continuity noise vector Δρ rel_MTA,J :

[0049] ΔR m_MTA,J =[R m_2 -R m_1 R m_3 -R m_2 ...R m_N -R m_N-1 ]

[0050] Δρ rel_MTA,J =[ρ2-ρ1ρ3-ρ2...ρ N -ρ N-1 ]

[0051] S6.3: The distance continuity noise vector ΔR m_MTA,J The elements in are used as weight factors of the nonlinear weighted function to construct the distance nonlinear weighted kernel function The relative reflectivity continuity noise vector Δρ rel_MTA,J The elements in are used as weight factors of the nonlinear weighting function to construct the relative reflectivity nonlinear weighted kernel function

[0052]

[0053] Where a1, b1, c1 are the coefficients of the nonlinear weighted kernel function of distance, a2, b2, c2 are the coefficients of the nonlinear weighted kernel function of relative reflectivity, and i≤N-1.

[0054] S6.4: Using the distance nonlinear weighted kernel function as the weight to calculate the distance continuity noise energy model The nonlinear weighted kernel function of relative reflectivity is used as the weight to calculate the reflectivity continuity noise energy model

[0055]

[0056] In the formula, l is the size of the neighborhood calculation block, and k is the number of neighborhoods divided according to l;

[0057] S6.5: Based on the characteristics of the maximum laser emission repetition frequency PRR and high scanning density of the mapping laser radar, there is a similarity between the distance and reflectivity between adjacent scanning points in space. When the continuous noise energy is minimized, the MTA solution result is obtained. and

[0058] S6.6: Judgment and Are they equal?

[0059] like and If they are equal, the solution is completed, and the multi-echo in the air corresponding to the laser echo is the result obtained by S6.5;

[0060] like and If they are not equal, adjust the coefficients of the distance nonlinear weighted kernel function and the relative reflectivity nonlinear weighted kernel function in S6.3, and return to S6.4.

[0061] A laser radar aerial multi-echo solution device based on distance and reflectivity constraints, characterized in that it includes one or more processors for implementing a laser radar aerial multi-echo solution method based on distance and reflectivity constraints.

[0062] An electronic device, comprising:

[0063] one or more processors;

[0064] A storage device is used to store one or more programs. When the one or more programs are executed by the electronic device, the electronic device implements a laser radar aerial multi-echo solution method based on distance and reflectivity constraints.

[0065] A computer-readable storage medium stores a program, which, when executed by a processor, implements a laser radar aerial multi-echo solution method based on distance and reflectivity constraints.

[0066] Compared with the prior art, the present invention has the following beneficial effects:

[0067] The method for solving multi-echoes in the air of a laser radar based on distance and reflectivity constraints of the present invention constructs spatial continuous noise based on the dual constraints of distance and reflectivity, and utilizes a nonlinear weighting function to nonlinearly amplify the influence of the continuous noise, thereby greatly improving the sensitivity of the weighting function to slight changes in the continuous noise; the laser radar distance, angle and reflectivity are calibrated and corrected, and the measurement consistency of the original data is improved from the aspect of basic data attributes, thereby ensuring the final nonlinear weighted solution accuracy and robustness, thereby realizing high-precision solution of multi-echo time in the air of a surveying and mapping laser radar at a long effective distance and a high laser emission repetition rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 The present invention is a flow chart of the method for solving multi-echo aerial laser radar based on distance and reflectivity constraints.

[0069] Figure 2 Schematic diagram of MTA for constant laser emission repetition frequency.

[0070] Figure 3 Schematic diagram of the laser radar scanning pitch direction and each continuous point in space.

[0071] Figure 4 Schematic diagram of the continuity of distances between adjacent points on the scanned surface.

[0072] Figure 5 This is a schematic diagram of a specific implementation flow of step S6.

[0073] Figure 6 Schematic diagram of neighborhood block size and number of blocks during MTA solution. DETAILED DESCRIPTION

[0074] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the implementation mode is described below with reference to the accompanying drawings.

[0075] The above and other technical contents, features and effects of the present invention are clearly presented in the following detailed description of the specific implementation modes in conjunction with the accompanying drawings. Through the description of the specific implementation modes, the technical means and effects adopted by the present invention to achieve the predetermined purpose can be more deeply and specifically understood. However, the attached drawings are only for reference and explanation purposes and are not used to limit the technical solutions of the present invention.

[0076] The method for solving multi-echo aerial laser radar based on distance and reflectivity constraints in this embodiment is as follows: Figure 1As shown in the figure: First, the measurement indication correction related to the target set and radiation properties is performed, including distance, angle, amplitude and relative reflectivity, to ensure the consistency and accuracy of the measurement results; the neighborhood is divided to determine the adjacent laser scanning points; the statistical weights of the characteristic parameters of the adjacent points are calculated and placed in different MTAs, and the characteristic parameters include distance and reflectivity; the real MTA is determined based on the result of the weight function. The specific steps include the following:

[0077] S1: Establish the geometric calibration equation of the surveying laser radar to correct the distance measurement indication and angle measurement indication of each echo;

[0078] Specifically, S1 includes:

[0079] According to the distance measurement principle of surveying laser radar, and referring to the existing distance correction technology of laser rangefinder, a mathematical model of laser radar distance correction is established;

[0080] And calculate the corrected distance measurement indication R m :

[0081] R m =R0+a R R0+b R

[0082] Where R0 is the original measured value of the distance, a R is the distance multiplication constant, b R is the distance measurement constant; by referring to the distance calibration technology of the photoelectric rangefinder, the distance indication is calibrated to obtain a R and b R ;

[0083] According to the scanning angle measurement principle of surveying laser radar, referring to the angle correction technology of theodolite and total station, the laser radar angle measurement correction equation is established, including the pitch angle correction equation and the azimuth angle correction mathematical equation, and the corrected pitch angle and azimuth angle are calculated:

[0084] θ m =θ0+a θ ·θ0+b θ

[0085] In the formula, θ m is the original measured value of the pitch angle, a θ is the pitch angle multiplied by a constant, b θ is the pitch angle constant; the pitch angle measurement indication is calibrated by referring to the pitch angle calibration technology of the photoelectric goniometer, and a is obtained θ and b θ ;

[0086]

[0087] In the formula, is the original measurement indication of azimuth, is the azimuth collimation axis correction constant, is the azimuth trunnion correction constant; the azimuth measurement indication is calibrated by referring to the azimuth calibration technology of the photoelectric goniometer, and the and

[0088] S2: Establish the mapping lidar radiation calibration equation to correct the amplitude and relative reflectivity of each echo.

[0089] Specifically, S2 includes:

[0090] According to the detection response principle of surveying and mapping laser radar, and referring to the existing photoelectric sensing detection technology, the laser radar echo amplitude correction equation is established, and the corrected echo amplitude is calculated:

[0091]

[0092] Where P echo is the echo response power, P DL It is the minimum detectable power of the mapping lidar system;

[0093] According to the detection response principle of surveying and mapping laser radar, based on the relationship between the detection response amplitude of the laser detection system and the relative reflectivity, a standard diffuse reflection whiteboard that has been calibrated by metrology is used as the traceability reference of the laser radar relative reflectivity standard, and the laser radar echo relative reflectivity correction equation is established:

[0094] ρ rel =A mp_echo -A mp_ref (R m )

[0095] In the formula, A mp_ref (R m ) is the reference diffuse reflection white plate at a distance R m The echo amplitude at .

[0096] S3: Based on the distance measurement indication corrected for each echo of the mapping laser radar, the time interval ΔT of the farthest laser echo is determined using the time flight principle max :

[0097]

[0098] Where c is the speed of light.

[0099] S4: Determine the time interval ΔT of the farthest laser echo based on the laser emission repetition frequency PRR of the mapping laser radar max The number of laser emission main waves N present in:

[0100] N=ΔT max ·PRR

[0101] Figure 2 The diagram is given in Figure 1, where i represents the main wave of the transmission, j represents the echo, τ is the transmission repetition period, and T m,MTA1 、T m-1,MTA2 、T m-2,MTA3 、T m-2,MTA4 are the times of four different MTAs corresponding to echo j. N is the number of main waves emitted by the laser, and also the number of multiple echoes (MTA) in the air.

[0102] S5: Determine adjacent continuous scanning points in the pitch direction according to the scanning pitch angle; determine adjacent continuous scanning points in the azimuth direction according to the scanning azimuth angle.

[0103] Figure 3 The adjacent continuous scanning points in the pitch direction are shown in FIG. The specific determination method includes:

[0104] By modifying the pitch angle after positive measurement, the indicated value θ m Continuity judgment is performed to obtain the spatial proximity points within a scan line. If |θ m,i -θ m,i-1 |=θ m,res , then it is judged as a continuous adjacent point in the pitch direction, where θ m,res is the LiDAR elevation angle measurement resolution and a fixed parameter for the mapping LiDAR system.

[0105] Figure 4 A schematic diagram of adjacent continuous scanning points in the azimuth direction is given in FIG. The specific determination method includes:

[0106] The azimuth angle is corrected to measure the indicated value. Perform continuity judgment to obtain spatial continuous points in adjacent scan lines. If It is judged as a continuous adjacent point in the azimuth direction, where It is the azimuth measurement resolution of the mapping lidar and a fixed parameter of the mapping lidar system.

[0107] S6: According to the adjacent continuous scanning points in the pitch direction and azimuth direction, the continuity of the transmitted main wave is judged. When the transmitted main wave is a continuous main wave, the continuous noise energy is calculated based on the geometric and radiation continuity between adjacent continuous scanning points using the ranging results and relative reflectivity results of each echo of the mapping laser radar. The continuity noise function corresponding to each multi-echo in the air is obtained, and a robust nonlinear optimization model is constructed and optimized to solve the multi-echo problem in the air.

[0108] like Figure 2 As shown, confirm Figure 2The emitted main wave in is a continuous main wave. Figure 4 A schematic diagram of the continuity of adjacent points scanned in the azimuth direction of the laser radar is given.

[0109] Specifically, Figure 5 As shown, S6 includes:

[0110] S6.1: Based on the number of laser emission main waves N, construct the corrected distance vector R corresponding to each possible MTA of each echo m_MTA,j and the relative reflectivity vector ρ rel_MTA,j :

[0111] R m_MTA,j =[R m_1 R m_2 ...R m_N ]

[0112] ρ rel_MTA,j =[ρ rel_1 ρ rel_2 ... rel_N ]

[0113] Wherein, j corresponds to the number of multi-echoes in air (MTA) calculated in S4, and j≤N.

[0114] S6.2: Construct the distance continuity noise vector ΔR according to S6.1 m_MTA,J and the relative reflectivity continuity noise vector Δρ rel_MTA,J :

[0115] ΔR m_MTA,J =[R m_2 -R m_1 R m_3 -R m_2 ...R m_N -R m_N-1 ]

[0116] Δρ rel_MTA,J =[ρ2-ρ1ρ3-ρ2...ρ N -ρ N-1 ]

[0117] S6.3: Substitute the distance continuity noise vector ΔR in S6.2 m_MTA,J The elements in are used as weight factors of the nonlinear weighted function to construct the distance nonlinear weighted kernel function The relative reflectivity continuity noise vector Δρ in S6.2 is rel_MTA,J The elements in are used as weight factors of the nonlinear weighting function to construct the relative reflectivity nonlinear weighted kernel function

[0118]

[0119] Where a1, b1, c1 are the coefficients of the nonlinear weighted kernel function of distance, a2, b2, c2 are the coefficients of the nonlinear weighted kernel function of relative reflectivity, and i≤N-1.

[0120] S6.4: Calculate the distance continuity noise energy using the distance nonlinear weighted kernel function as the weight The relative reflectivity nonlinear weighted kernel function is used as the weight to calculate the reflectivity continuity noise energy.

[0121]

[0122] In the formula, l is the size of the neighborhood calculation block, k is the number of neighborhoods divided according to l, and the schematic diagram of l and k is as follows: Figure 6 shown.

[0123] S6.5: Based on the characteristics of the maximum laser emission repetition frequency PRR and high scanning density of the mapping laser radar, there is a similarity between the distance and reflectivity between adjacent scanning points in space. When the continuous noise energy is minimized, the MTA solution result is obtained. and

[0124] S6.6: Judgment and Are they equal?

[0125] like and If they are equal, the solution is completed, and the MTA corresponding to the laser echo is the result obtained by S115;

[0126] like and If they are not equal, adjust the distance nonlinear weighted kernel function coefficient and the relative reflectivity nonlinear weighted kernel function coefficient in S6.3 and return to S6.4.

[0127] It should be noted that the reference technologies used in the present invention, including the distance correction technology of the photoelectric rangefinder, the angle correction technology of the photoelectric goniometer, the laser radar detection equation, and the reflectivity calibration technology of the photoelectric detection system are all mature methods in the prior art, and the specific steps will not be repeated here.

[0128] The method for solving the multi-echo in the air of the surveying and mapping laser radar of this embodiment establishes a method for constructing spatial continuous noise based on the dual constraints of distance and reflectivity, and uses a nonlinear weighting function to nonlinearly amplify the influence of continuous noise, greatly improving the sensitivity of the weighting function to slight changes in continuous noise. The laser radar distance, angle and reflectivity are calibrated and corrected to improve the measurement consistency of the original data from the basic data attributes, ensuring the accuracy and robustness of the solution after the final nonlinear weighting, thereby achieving high-precision solution of the multi-echo time in the air of the surveying and mapping laser radar at a long range and high laser emission repetition rate.

[0129] Corresponding to the aforementioned embodiment of the laser radar aerial multi-echo solution method based on distance and reflectivity constraints, the present invention also provides an embodiment of the laser radar aerial multi-echo solution device based on distance and reflectivity constraints.

[0130] The laser radar aerial multi-echo solution device based on distance and reflectivity constraints provided in an embodiment of the present invention includes one or more processors for implementing the laser radar aerial multi-echo solution method based on distance and reflectivity constraints in the above embodiment.

[0131] The embodiment of the laser radar aerial multi-echo solution device based on distance and reflectivity constraints of the present invention can be applied to any device with data processing capabilities, and the arbitrary device with data processing capabilities can be a device or apparatus such as a computer. The device embodiment can be implemented by software, or by hardware or a combination of software and hardware. Taking software implementation as an example, as a device in a logical sense, it is formed by the processor of any device with data processing capabilities in which it is located to read the corresponding computer program instructions in the non-volatile memory into the memory and run it. From the hardware level, in addition to the processor, memory, network interface, and non-volatile memory, the arbitrary device with data processing capabilities in which the device in the embodiment is located can also include other hardware according to the actual function of the arbitrary device with data processing capabilities, which will not be described in detail.

[0132] The implementation process of the functions and effects of each unit in the above-mentioned device is specifically described in the implementation process of the corresponding steps in the above-mentioned method, and will not be repeated here.

[0133] For the device embodiment, since it basically corresponds to the method embodiment, the relevant parts can refer to the partial description of the method embodiment. The device embodiment described above is only schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of the present invention. Ordinary technicians in this field can understand and implement it without paying creative work.

[0134] An embodiment of the present invention also provides a computer-readable storage medium having a program stored thereon. When the program is executed by a processor, the method for solving multi-echo aerial laser radar based on distance and reflectivity constraints in the above embodiment is implemented.

[0135] The computer-readable storage medium may be an internal storage unit of any device with data processing capability described in any of the aforementioned embodiments, such as a hard disk or a memory. The computer-readable storage medium may also be an external storage device, such as a plug-in hard disk, a smart media card (SMC), an SD card, a flash card, etc. equipped on the device. Furthermore, the computer-readable storage medium may also include both an internal storage unit of any device with data processing capability and an external storage device. The computer-readable storage medium is used to store the computer program and other programs and data required by any device with data processing capability, and may also be used to temporarily store data that has been output or is to be output.

[0136] Those skilled in the art can understand that the above are only preferred examples of the invention and are not intended to limit the invention. Although the invention is described in detail with reference to the above examples, those skilled in the art can still modify the technical solutions recorded in the above examples or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, etc. made within the spirit and principle of the invention shall be included in the protection scope of the invention.

Claims

1. A method for solving multi-echoes in the air of a laser radar based on distance and reflectivity constraints, characterized in that: The method comprises the following steps: S1: Establish the geometric calibration equation of the surveying laser radar to correct the distance measurement indication and angle measurement indication of each echo; S2: Establish the mapping lidar radiation calibration equation to correct the amplitude and relative reflectivity of each echo; S3: Based on the distance measurement indication corrected by each echo of the mapping laser radar, the time interval of the farthest laser echo is determined using the time flight principle; S4: determining the number of laser emission main waves existing in the time interval of the farthest laser echo according to the laser emission repetition frequency of the surveying and mapping laser radar; S5: determining adjacent continuous scanning points in the pitch direction according to the scanning pitch angle; determining adjacent continuous scanning points in the azimuth direction according to the scanning azimuth angle; S6: According to the adjacent continuous scanning points in the pitch direction and azimuth direction, the continuity of the transmitted main wave is judged. When the transmitted main wave is a continuous main wave, the continuous noise energy is calculated based on the geometric and radiation continuity between adjacent continuous scanning points using the ranging results and relative reflectivity results of each echo of the mapping laser radar. The continuity noise function corresponding to each multi-echo in the air is obtained, and a robust nonlinear optimization model is constructed and optimized to solve the multi-echo problem in the air.

2. The method for solving multi-echo aerial laser radar based on distance and reflectivity constraints according to claim 1 is characterized in that: The S1 specifically includes: According to the distance measurement principle of surveying laser radar, referring to the distance correction technology of laser rangefinder, the laser radar distance measurement correction equation is established, and the corrected distance measurement indication R is calculated. m : ； Where R0 is the original measured value of the distance, a R is the distance multiplication constant, b R is the distance measurement constant; by referring to the distance calibration technology of the photoelectric rangefinder, the distance indication is calibrated to obtain a R and b R ; According to the scanning angle measurement principle of surveying laser radar, referring to the angle correction technology of theodolite and total station, the laser radar angle measurement correction equation is established, including the pitch angle correction equation and the azimuth angle correction mathematical equation, and the corrected pitch angle and azimuth angle are calculated: ； In the formula, θ m is the original measured value of the pitch angle, a θ is the pitch angle multiplied by a constant, b θ is the pitch angle constant; the pitch angle measurement indication is calibrated by referring to the pitch angle calibration technology of the photoelectric goniometer, and a is obtained θ and b θ ; ； In the formula, is the original measurement indication of azimuth, is the azimuth collimation axis correction constant, is the azimuth trunnion correction constant; the azimuth measurement indication is calibrated by referring to the azimuth calibration technology of the photoelectric goniometer, and the and .

3. The method for solving multi-echo in air of laser radar based on distance and reflectivity constraints according to claim 2 is characterized in that: The S2 specifically includes: According to the detection response principle of surveying and mapping laser radar, referring to the photoelectric sensing detection technology, the laser radar echo amplitude correction equation is established, and the corrected echo amplitude is calculated: ； Where P echo is the echo response power, P DL It is the minimum detectable power of the mapping lidar system; According to the detection response principle of surveying and mapping laser radar, based on the relationship between the detection response amplitude of the laser detection system and the relative reflectivity, a standard diffuse reflection whiteboard that has been calibrated by metrology is used as the traceability reference of the laser radar relative reflectivity standard, and the laser radar echo relative reflectivity correction equation is established: ； In the formula, A mp_echo is the echo amplitude, A mp_ref (R m ) is the reference diffuse reflection white plate at a distance R m The echo amplitude at .

4. The method for solving multi-echo aerial laser radar based on distance and reflectivity constraints according to claim 3 is characterized in that: The time interval of the farthest laser echo The calculation formula is as follows: ； Where c is the speed of light.

5. The method for solving multi-echo aerial laser radar based on distance and reflectivity constraints according to claim 4 is characterized in that: The calculation formula for the number N of laser emission main waves existing in the time interval of the farthest laser echo in S4 is as follows: ； Where PRR is the laser emission repetition frequency.

6. The method for solving multi-echo aerial laser radar based on distance and reflectivity constraints according to claim 5 is characterized in that: The S5 specifically includes: By modifying the positive pitch angle measurement indication θ m Perform continuity judgment to obtain the spatial proximity points within a scan line. If , then it is judged as a continuous adjacent point in the pitch direction, where θ m,res is the LiDAR elevation angle measurement resolution; The azimuth measurement indication is corrected Perform continuity judgment to obtain spatial continuous points between adjacent scan lines. If , then it is judged as a continuous adjacent point in the azimuth direction, where Azimuth measurement resolution for mapping lidar.

7. The method for solving multi-echo aerial laser radar based on distance and reflectivity constraints according to claim 6 is characterized in that: The S6 specifically includes: S6.1: Based on the number of laser emission main waves N, construct the corrected distance vector corresponding to each possible multiple echo in the air and the relative reflectivity vector : ； ； Where, j corresponds to the number of multi-echoes in the air obtained by calculating S4, and j≤N; S6.2: Construct distance continuity noise vectors separately and the relative reflectivity continuity noise vector : ； ； S6.3: The distance continuity noise vector The elements in are used as weight factors of the nonlinear weighted function to construct the distance nonlinear weighted kernel function ; The relative reflectivity continuity noise vector The elements in are used as weight factors of the nonlinear weighting function to construct the relative reflectivity nonlinear weighted kernel function : ； ； Where a1, b1, c1 are the coefficients of the nonlinear weighted kernel function of distance, a2, b2, c2 are the coefficients of the nonlinear weighted kernel function of relative reflectivity, i≤N-1; S6.4: Using the distance nonlinear weighted kernel function as the weight to calculate the distance continuity noise energy model , the nonlinear weighted kernel function of relative reflectivity is used as the weight to calculate the reflectivity continuity noise energy model : ； ； In the formula, l is the size of the neighborhood calculation block, and k is the number of neighborhoods divided according to l; S6.5: Based on the maximum laser emission repetition frequency of the mapping laser radar With the characteristics of high scanning density, there is a similarity between the distance and reflectivity between adjacent scanning points in space. Rm When the continuous noise energy is minimum, the MTA solution result is obtained. and ; S6.6: Judgment and Are they equal? like and If they are equal, the solution is completed, and the multi-echo in the air corresponding to the laser echo is the result obtained by S6.5; like and If they are not equal, adjust the coefficients of the distance nonlinear weighted kernel function and the relative reflectivity nonlinear weighted kernel function in S6.3, and return to S6.

4.

8. A laser radar aerial multi-echo solution device based on distance and reflectivity constraints, characterized in that: It includes one or more processors for implementing the laser radar aerial multi-echo solution method based on distance and reflectivity constraints as described in any one of claims 1 to 7.

9. An electronic device, characterized in that: include: one or more processors; A storage device for storing one or more programs, which, when executed by the electronic device, enables the electronic device to implement the laser radar aerial multi-echo solution method based on distance and reflectivity constraints as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: A program is stored thereon, and when the program is executed by a processor, the method for solving multi-echo aerial laser radar based on distance and reflectivity constraints as described in any one of claims 1 to 7 is implemented.

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