DSM reconstruction method, system and device based on airborne multi-angle InSAR

Abstract

The invention relates to a DSM reconstruction method, system and device based on airborne multi-angle InSAR, and the method comprises the steps: planning a multi-angle data obtaining task based on the topographic relief for a complex terrain of a measurement area, and obtaining a multi-angle route and radar parameters; performing multi-angle radar detection on the detection area based on the multi-angle air line and the radar parameters to obtain multi-angle SAR original echo data; carrying out data processing on the SAR original echo data at multiple angles by adopting an InSAR data processing method to obtain DSM data at multiple angles; and performing fusion processing on the DSM data at the multiple angles to obtain the DSM data of the complex terrain. According to the method, data acquisition tasks under multiple angles of topographic relief planning are considered, invalid DSM data caused by shadow and overlay can be avoided to the greatest extent, then high consistency of DSM data precision under each angle is ensured through InSAR data processing, and DSM high-precision reconstruction of a multi-angle InSAR system complex terrain is realized.

Description

Technical Field

[0001] The present invention relates to the field of radar geographic information mapping, and particularly to a DSM reconstruction method, system and device based on airborne multi-angle InSAR. Background Art

[0002] InSAR technology is derived from Synthetic Aperture Radar (SAR) technology, and has achieved a breakthrough in expanding the radar two-dimensional imaging to the three-dimensional imaging dimension. Due to the all-weather, all-day, high-resolution and wide-swath DEM data acquisition capabilities of InSAR, great application benefits have been generated. Among them, the foreign TanDEM-X system and China's Tianhui-2 satellite system are both typical representatives of spaceborne InSAR systems, and the foreign MEMPHIS and China's millimeter-wave InSAR are both typical representatives of airborne InSAR systems. However, how to effectively use InSAR technology to obtain DSM (Digital Surface Model) of large areas with high-precision complex terrain is still a difficult problem to be solved at present. Because in complex terrain areas, the side-looking imaging of SAR is prone to form a large range of shadows and severe layover phenomena in steep terrain areas. The shadow and layover areas are manifested as the loss of information in the SAR image, resulting in a large area of invalid data in the DSM data, seriously affecting the quality and application of the DSM data.

[0003] In the currently existing public technologies, the main technical means are multi-baseline InSAR system, multi-frequency InSAR system combined with DSM data interpolation and multi-source data fusion, and no solution for multi-angle InSAR system has been seen. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a DSM reconstruction method, system and device based on airborne multi-angle InSAR, which uses the multi-angle InSAR system to achieve high-precision reconstruction of DSM for complex terrain, and solves the problem of low DSM reconstruction accuracy caused by invalid DSM data.

[0005] The technical solution of the present invention to solve the above technical problems is as follows:

[0006] First aspect:

[0007] The present invention provides a DSM reconstruction method based on airborne multi-angle InSAR, and the DSM reconstruction method includes:

[0008] S1. For the complex terrain of the measurement area, plan the data acquisition tasks at multiple angles based on the terrain undulation to obtain the flight routes and radar parameters at multiple angles; based on the flight routes and radar parameters at multiple angles, conduct radar detection on the measurement area at multiple angles to obtain the SAR raw echo data at multiple angles;

[0009] S2. Use a high-precision InSAR data processing method to process the SAR raw echo data at multiple angles to obtain DSM data at multiple angles.

[0010] S3. Perform fusion processing on the DSM data at multiple angles to obtain DSM data for complex terrain.

[0011] Based on the above technical solutions, the present invention can also be improved as follows.

[0012] Further, the specific content of S1 is as follows:

[0013] S11. For the complex terrain of the survey area, plan multiple data acquisition flight lines based on multiple angles.

[0014] S12. Taking the scope of the survey area and the technical indicators of the InSAR radar as constraint conditions, statistically calculate the slope and aspect of the survey area based on the coarse-precision DSM data of the survey area, and optimize the parameters of the data acquisition flight lines at each angle according to the slope and aspect of the survey area to obtain the optimized flight line parameters at each angle.

[0015] S13. Taking the scope of the survey area and the technical indicators of the InSAR radar as constraint conditions, optimize the InSAR radar parameters of the data acquisition flight lines at the corresponding angles according to the slope and aspect of the survey area and the optimized flight line parameters at each angle to obtain the optimized InSAR radar parameters at each angle.

[0016] S14. Based on the coarse-precision DSM data of the survey area, as well as the optimized flight line parameters and InSAR radar parameters at each angle, calculate the layover areas and shadow areas at each angle in the survey area.

[0017] S15. Determine whether the layover areas and shadow areas at each angle in the survey area meet the preset requirements; if so, combine the optimized flight line parameters and InSAR radar parameters at each angle as the flight line and radar parameters at the corresponding angle; if not, return to S12 and execute it cyclically until the layover areas and shadow areas at each angle in the survey area meet the preset requirements, and combine the optimized flight line parameters and InSAR radar parameters in the last cycle at each angle as the flight line and radar parameters at the corresponding angle.

[0018] S16. Based on the flight line and radar parameters at each angle, perform radar detection on the survey area at the corresponding angle to obtain the SAR raw echo data at each angle.

[0019] Further, the parameters of the data acquisition flight line include: flight line direction, flight line length, and flight line height.

[0020] The InSAR radar parameters include: the side-looking direction, the depression angle, the signal bandwidth, the signal pulse width, and the sampling starting point of the InSAR radar.

[0021] Furthermore, during the process of calculating the layover area, the determination condition for the layover area is:

[0022] The included angle between the incident signal of the InSAR radar and the uphill slope in the survey area is less than 90 degrees.

[0023] Furthermore, during the process of calculating the shadow area, the determination condition for the shadow area is:

[0024] The signal incident angle of the InSAR radar is less than the slope of the back slope in the survey area.

[0025] Furthermore, the specific content of S15 is

[0026] Statistically calculate the total area of the survey area to obtain the total area of the survey area; statistically calculate the total area of all layover areas in the survey area to obtain the total area of the layover area; statistically calculate the total area of all shadow areas in the survey area to obtain the total area of the shadow area;

[0027] Perform an addition operation on the total area of the layover area and the total area of the shadow area to obtain the total area of the invalid data area; divide the total area of the invalid data area by the total area of the survey area to obtain the proportion of the total area of the invalid data area;

[0028] Calculate the area of the isolated and largest layover area among all layover areas to obtain the area of the largest isolated layover area; calculate the area of the isolated and largest shadow area among all shadow areas to obtain the area of the largest isolated shadow area;

[0029] When the proportion of the total area of the invalid data area is less than or equal to the preset area proportion threshold, and the area of the largest isolated layover area is less than or equal to the preset invalid data area threshold, and the area of the largest isolated shadow area is less than or equal to the preset invalid data area threshold, it is determined that the layover area and the shadow area in the survey area meet the preset requirements, and the combination of the route optimization parameters and the InSAR radar optimization parameters is used as the route and radar parameters; otherwise, it is determined that the layover area and the shadow area in the survey area do not meet the preset requirements, and the S12 is returned to execute in a loop until the layover area and the shadow area in the survey area meet the preset requirements, and the combination of the route optimization parameters and the InSAR radar optimization parameters in the last loop is used as the route and radar parameters.

[0030] Furthermore, the specific content of S2 is:

[0031] Obtain the imaging parameters and internal calibration parameters at each angle, and correct the amplitude-phase error and system delay error of the SAR raw echo data at the corresponding angle through the internal calibration parameters at each angle; extract the motion compensation reference trajectory and process the Doppler parameters using the POS post-processing data at each angle to implement the imaging processing of the SAR raw echo data at each angle, and obtain the SAR main image and SAR auxiliary image at each angle;

[0032] According to the coordinate mapping relationship between the homologous points of the SAR main image and the SAR auxiliary image at each angle, resample the SAR auxiliary image at the corresponding angle to the same pixel grid as the SAR main image to achieve the registration between the SAR auxiliary image and the SAR main image at each angle, and obtain the registered SAR auxiliary image and coherence coefficient at each angle;

[0033] Based on the coherence coefficient at each angle, perform image interference processing on the SAR main image and the registered SAR auxiliary image at the corresponding angle to obtain the interference phase at each angle;

[0034] According to the InSAR working principle, perform flat-earth effect removal processing on the interference phase at each angle to obtain the flat-earth removed interference phase at each angle;

[0035] Based on the coherence coefficient, use the quality map-guided SIGMA adaptive filtering method to filter the flat-earth removed interference phase at each angle to obtain the filtered interference phase at each angle;

[0036] Based on the coherence coefficient, use the quality map-guided fast phase unwrapping method to perform phase unwrapping on the filtered interference phase at each angle to obtain the unwrapped phase at each angle;

[0037] Based on the coherence coefficient, filter the unwrapped phase at each angle to obtain the filtered unwrapped phase at each angle;

[0038] Perform interference calibration on the filtered unwrapped phase at each angle to obtain the interference calibration parameters at each angle;

[0039] Based on the airborne InSAR working principle, perform parameter correction and elevation calculation according to the imaging parameters, filtered unwrapped phase and interference calibration parameters at each angle to obtain the DSM data at each angle.

[0040] Further, the specific content of S3 is as follows:

[0041] Based on the multi-threaded parallel computing resources of the GPU platform, use the CUDA programming model to perform fast projection conversion on the DSM data at each angle to generate a regular grid point cloud; where the regular grid point cloud includes a regular grid elevation point cloud, a regular grid coherence coefficient point cloud and a regular grid interference phase point cloud;

[0042] Weighted filtering is performed on the regular grid elevation point cloud at a corresponding angle by using the gradients of the regular grid coherence coefficient point cloud and the regular grid interference phase point cloud at each angle to obtain the regular grid elevation filtered point cloud at each angle;

[0043] The regular grid elevation filtered point clouds at all angles are subjected to multi-angle data fusion to obtain complex terrain DSM data.

[0044] Second aspect:

[0045] Based on the above method for reconstructing DSM based on airborne multi-angle InSAR, the present invention further provides a system for reconstructing DSM based on airborne multi-angle InSAR, and the DSM reconstruction system includes:

[0046] A data acquisition module, which is used to plan data acquisition tasks at multiple angles based on the complex terrain of the measurement area to obtain flight lines and radar parameters at multiple angles; based on the flight lines and radar parameters at multiple angles, perform radar detection on the measurement area at multiple angles to obtain SAR raw echo data at multiple angles;

[0047] A data processing module, which is used to process the SAR raw echo data at multiple angles by using a high-precision InSAR data processing method to obtain DSM data at multiple angles;

[0048] A data fusion module, which is used to perform fusion processing on the DSM data at multiple angles to obtain complex terrain DSM data.

[0049] Third aspect:

[0050] Based on the above method for reconstructing DSM based on airborne multi-angle InSAR, the present invention further provides a device for reconstructing DSM based on airborne multi-angle InSAR, and the DSM reconstruction device includes: a processor, a memory, and a computer program stored in the memory, and when the computer program is executed by the processor, it implements the method for reconstructing DSM based on airborne multi-angle InSAR as described above.

[0051] The beneficial effects of the present invention are as follows: in the method, system and device for reconstructing DSM based on airborne multi-angle InSAR of the present invention, the terrain undulation is considered, and the data acquisition tasks at multiple angles are planned, which can avoid the invalid DSM data caused by shadow and layover to the greatest extent. Then, through high-precision InSAR data processing, the high consistency of the DSM data accuracy at each angle is ensured; the present invention proposes to achieve high-precision reconstruction of complex terrain DSM in the multi-angle InSAR system through fast multi-angle DSM data fusion processing. Description of the Drawings

[0052] Figure 1is the working principle diagram of InSAR;

[0053] Figure 2 is the schematic diagram of layover and shadow generation;

[0054] Figure 3 is the flow chart of a DSM reconstruction method based on airborne multi-angle InSAR of the present invention;

[0055] Figure 4 is the flow chart of S1 in a DSM reconstruction method based on airborne multi-angle InSAR of the present invention;

[0056] Figure 5 is the flow chart of S2 in a DSM reconstruction method based on airborne multi-angle InSAR of the present invention;

[0057] Figure 6 is the flow chart of S3 in a DSM reconstruction method based on airborne multi-angle InSAR of the present invention;

[0058] Figure 7 is the structural block diagram of a DSM reconstruction system based on airborne multi-angle InSAR of the present invention. Detailed implementation manners

[0059] The principles and features of the present invention will be described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0060] InSAR obtains two SAR images with a certain view angle difference and correlation in the same observation area at the same time by two antennas or at different times by one antenna. After interference processing, the phase difference between them is obtained, and then the terrain height of the observation area, that is, DSM data, is obtained. The working principle of InSAR is as Figure 1 shown.

[0061] Figure 1 In, A1 and A2 respectively represent the positions of the two antennas. The distance between the two antennas is the baseline length B, and the angle between the baseline and the horizontal direction is the baseline inclination angle α. H represents the platform height, and θ represents the downward viewing angle of the first antenna. P represents the ground target, whose height is h. The slant range from antenna A1 to P is R1, and the slant range from antenna A2 to P is R2, and R2 = R1 + ΔR. According to Figure 1 the geometric relationship in, it can be obtained that:

[0062] h = H - R1cosθ; (1)

[0063]

[0064] In Equation (3), in the single - transmit and single - receive mode, ρ = 2; in the single - transmit and double - receive mode, ρ = 1; Δφ represents the absolute interference phase; λ represents the wavelength. According to Equations (2) and (3), h in Equation (1) can be calculated.

[0065] Figure 2 It is the schematic diagram of layover and shadow generation. M represents the position of the radar, and the figure composed of BCEF represents the hillside, where BC represents the up - slope and EF represents the down - slope. The dashed lines where MA, MB, MC, MD, and MEG are located represent the propagation paths of radar signals, and the arcs where AC, BD, E, and G are located represent the isoslant - range lines. When the radar irradiates the hillside, if the slope angle of the hillside is large, the slant - range from the top of the slope to the radar satellite is less than that from the bottom of the slope to the radar satellite, resulting in the phenomenon that the top of the slope is recorded first and the bottom of the slope is recorded later in the SAR image. As a result, the echo signals from several different regions are projected onto the same SAR image cell, causing the InSAR interference signals to be intertwined, which is the layover area. See the area formed by points A, C and points B, D in Figure 2 When the radar satellite irradiates the back of the hillside, if the slope angle of the back is too large, the radar beam is blocked by the mountain top and cannot irradiate the target area on the back of the mountain body, resulting in no echo signal in this area and no data at the corresponding InSAR interference phase, which is the shadow area. See the area formed by points E, F, G in the appendix Figure 2

[0066] The shadow area and the layover area are manifested as the loss of information in the SAR image, resulting in a large area of invalid data in the DSM data, seriously affecting the quality and application of the DSM data.

[0067] To solve the above problems, the specific solution provided by the present invention is as follows:

[0068] The first aspect:

[0069] As Figure 3 shown, the present invention provides a DSM reconstruction method based on airborne multi - angle InSAR. The DSM reconstruction method includes:

[0070] S1. For the complex terrain of the measurement area, plan the data acquisition tasks at multiple angles based on the terrain undulation to obtain the flight paths and radar parameters at multiple angles; based on the flight paths and radar parameters at multiple angles, conduct radar detection of the measurement area at multiple angles to obtain the SAR raw echo data at multiple angles;

[0071] S2. Use a high - precision InSAR data processing method to process the SAR raw echo data at multiple angles to obtain the DSM data at multiple angles;

[0072] ​S3. Perform fusion processing on DSM data from multiple angles to obtain complex terrain DSM data.

[0073] Through the data acquisition task planning and design considering terrain undulations, the present invention maximally avoids invalid data caused by shadows and layovers; through high-precision InSAR data processing, it ensures a high degree of consistency in the accuracy of DSM data for each angle; through fast multi-angle DSM data fusion processing, it realizes high-precision reconstruction of complex terrain DSM in a multi-angle InSAR system.

[0074] In some embodiments, as Figure 4 shown, the specific content of S1 is as follows:

[0075] S11. For the complex terrain of the measurement area, plan multiple data acquisition flight lines based on multiple angles.

[0076] S12. Taking the scope of the measurement area and the technical indicators of the InSAR radar as constraint conditions, statistically calculate the slope and aspect of the measurement area based on the rough-precision DSM data of the measurement area, and optimize the parameters of the data acquisition flight lines at each angle according to the slope and aspect of the measurement area to obtain the optimized flight line parameters at each angle; among them, the parameters of the data acquisition flight line include: flight line direction, flight line length, and flight line height.

[0077] S13. Taking the scope of the measurement area and the technical indicators of the InSAR radar as constraint conditions, optimize the InSAR radar parameters of the data acquisition flight line at the corresponding angle according to the slope and aspect of the measurement area and the optimized flight line parameters at each angle to obtain the optimized InSAR radar parameters at each angle; among them, the InSAR radar parameters include: the side-looking direction of the InSAR radar, the down-view angle, the signal bandwidth, the signal pulse width, and the sampling starting point.

[0078] S14. Based on the rough-precision DSM data of the measurement area and the optimized flight line parameters and InSAR radar parameters at each angle, calculate the layover areas and shadow areas at each angle in the measurement area;

[0079] Specifically, based on the rough-precision DSM data of the measurement area, the optimized flight line parameters, and the optimized InSAR radar parameters, according to Figure 2 the geometric relationship of the layover area in, calculate the layover area; in Figure 2 , when the radar irradiates the uphill BC, the slant range gradually decreases from the bottom to the top of the slope, resulting in the phenomenon of top-bottom inversion of points B and C on the SAR image; while in the ABCD interval, the radar slant range first decreases and then increases as the ground range increases, which may cause the phenomenon that multiple echoes reach the radar receiver simultaneously in this area, and it appears as a brighter area on the SAR image, and this area is the layover area. In the process of calculating the layover area, the determination condition of the layover area is: the included angle between the incident signal of the InSAR radar and the uphill in the measurement area is less than 90 degrees, that is:

[0080]

[0081] Among them, γ1 represents the slope of the upslope, θ1 represents the downward viewing angle when the radar signal irradiates the bottom of the upslope, and β1 represents the incident angle when the radar signal irradiates the bottom of the upslope.

[0082] Specifically, based on the rough-precision DSM data of the survey area, the route optimization parameters, and the InSAR radar optimization parameters, according to Figure 2 the geometric relationship of the shaded area in Figure 2 for the EFG area, the radar signal is blocked by the CE segment, resulting in no echo signal in this area, which is the shaded area. In the process of calculating the shaded area, the determination condition of the shaded area is: the incident angle of the InSAR radar signal is less than the slope of the backslope in the survey area, that is:

[0083]

[0084] Among them, γ2 represents the slope of the backslope, θ2 represents the downward viewing angle when the radar signal irradiates the top of the backslope, and β2 represents the incident angle when the radar signal irradiates the top of the backslope.

[0085] In S15, judge whether the layover areas and shaded areas at each angle in the survey area meet the preset requirements; if so, combine the route optimization parameters and InSAR radar optimization parameters at each angle as the route and radar parameters at the corresponding angle; if not, return to the S12 loop and execute until the layover areas and shaded areas at each angle in the survey area meet the preset requirements, and combine the route optimization parameters and InSAR radar optimization parameters in the last loop at each angle as the route and radar parameters at the corresponding angle; where, the S15 is specifically:

[0086] Statistical the total area of the survey area to obtain the total area of the survey area; statistical the total area of all layover areas in the survey area to obtain the total area of the layover area; statistical the total area of all shaded areas in the survey area to obtain the total area of the shaded area;

[0087] Perform an addition operation on the total area of the layover area and the total area of the shaded area to obtain the total area of the invalid data area; divide the total area of the invalid data area by the total area of the survey area to obtain the proportion of the total area of the invalid data area;

[0088] Calculate the area of the largest isolated layover area among all layover areas to obtain the area of the largest isolated layover area; calculate the area of the largest isolated shaded area among all shaded areas to obtain the area of the largest isolated shaded area;

[0089] When the total area ratio of the invalid data region is less than or equal to a preset area ratio threshold, and the area of the largest isolated layover region is less than or equal to the preset invalid data region area threshold, and the area of the largest isolated shadow region is less than or equal to the preset invalid data region area threshold, it is determined that the layover region and the shadow region in the survey area meet the preset requirements, and the combination of the flight line optimization parameters and the InSAR radar optimization parameters is used as the flight line and radar parameters; otherwise, it is determined that the layover region and the shadow region in the survey area do not meet the preset requirements, and the loop of S12 is returned to execute until the layover region and the shadow region in the survey area meet the preset requirements, and the combination of the flight line optimization parameters and the InSAR radar optimization parameters in the last loop is used as the flight line and radar parameters.

[0090] That is to say, when the following three conditions are met simultaneously, it can be determined that the layover region and the shadow region meet the preset requirements:

[0091]

[0092] Among them, S layover represents the total area of the layover region, S shadow represents the total area of the shadow region, S represents the total area of the survey area, T p represents the preset area ratio threshold, (S layover ) max represents the area of the largest isolated layover region, (S shadow ) max represents the area of the largest isolated shadow region, T s represents the preset invalid data region area threshold.

[0093] S16. Based on the flight line and radar parameters at each angle, radar detection of the survey area is performed at the corresponding angle to obtain the SAR raw echo data at each angle.

[0094] In some embodiments, as Figure 5 shown, the S2 is specifically:

[0095] Obtain the imaging parameters and internal calibration parameters at each angle, and correct the amplitude-phase error and system delay error of the SAR raw echo data at the corresponding angle through the internal calibration parameters at each angle; after the correction of the amplitude-phase error and system delay error of the internal calibration is completed, use the POS post-processing data at each angle to extract the motion compensation reference trajectory and process the Doppler parameters to implement the imaging processing work of the SAR raw echo data at each angle, and obtain the SAR main image and SAR auxiliary image at each angle; among them, the correction of the amplitude-phase error and system delay error of the internal calibration is the key to realizing high-precision InSAR processing.

[0096] According to the coordinate mapping relationship between the corresponding points of the SAR main image and the SAR auxiliary image at each angle, resample the SAR auxiliary image at the corresponding angle to the same pixel grid as the SAR main image, so as to realize the registration between the SAR auxiliary image and the SAR main image at each angle, and obtain the registered SAR auxiliary image and the coherence coefficient at each angle; among them, resampling the SAR auxiliary image at the corresponding angle to the same pixel grid as the SAR main image is for a pair of pixel points of the SAR auxiliary image and the SAR main image to correspond to the same resolution cell on the ground.

[0097] Based on the coherence coefficients at each angle, perform image interference processing on the SAR main image and the registered SAR auxiliary image at the corresponding angle to obtain the interference phase (i.e., phase difference) at each angle.

[0098] According to the InSAR working principle, perform flat-earth effect removal processing on the interference phase at each angle to obtain the flat-earth removed interference phase at each angle; among them, performing flat-earth effect removal processing on the interference phase at each angle is specifically to compensate for the dense interference fringes with linear changes generated by the flat ground surface.

[0099] Based on the coherence coefficient, use the quality map-guided SIGMA adaptive filtering method to filter the flat-earth removed interference phase at each angle to obtain the filtered interference phase at each angle; specifically, due to the existence of interferences such as decoherence, layover, and shadow, it will affect the efficiency and accuracy of phase unwrapping. Therefore, the quality map-guided SIGMA adaptive filtering method is used to filter the flat-earth removed interference phase at each angle; interference phase filtering is the key to realizing high-precision InSAR processing.

[0100] Based on the coherence coefficient, use the quality map-guided fast phase unwrapping method to perform phase unwrapping on the filtered interference phase at each angle to obtain the unwrapped phase at each angle; among them, phase unwrapping is the process of restoring the wrapped interference phase to the absolute interference phase corresponding to the terrain elevation.

[0101] Based on the coherence coefficient, filter the unwrapped phase at each angle to obtain the filtered unwrapped phase at each angle.

[0102] Perform interference calibration on the filtered unwrapped phase at each angle to obtain the interference calibration parameters at each angle; among them, interference calibration is the key to realizing high-precision InSAR processing and is the premise to ensure the multi-angle InSAR data fusion; interference calibration is specifically the process of deriving the InSAR interference calibration model according to the InSAR working principle and iteratively solving the high-precision interference parameter deviation (interference calibration parameters).

[0103] Based on the working principle of airborne InSAR, parameter calibration and elevation calculation are performed according to the imaging parameters, filtered and unwrapped phases, and interferometric calibration parameters at each angle to obtain DSM data at each angle.

[0104] In some embodiments, as Figure 6 shown, the specific operation of S3 is as follows:

[0105] Fully utilize the multi-threaded parallel computing power resources of the GPU platform. According to the data structure characteristics of the oblique ground projection conversion model, design a parallel computing module with multi-level data block division based on the Compute Unified Device Architecture (CUDA) programming model to achieve fast projection conversion of massive point cloud data at multiple angles in a huge scene (i.e., the DSM data at each angle obtained in S2), and generate regular grid point clouds; among them, the regular grid point clouds include regular grid elevation point clouds, regular grid coherence coefficient point clouds, and regular grid interferometric phase point clouds;

[0106] Due to complex terrain and landforms, InSAR data may have invalid data or low-quality data in regular grid point clouds caused by layover, shadow, near-range compression, vegetation, water areas, etc. The regular grid coherence coefficient point cloud is an objective reflection of the quality of point cloud data, and the regular grid interferometric phase point cloud is an objective reflection of terrain undulation. Use the gradients of the regular grid coherence coefficient point cloud and the regular grid interferometric phase point cloud to perform weighted filtering on the regular grid elevation point cloud to obtain regular grid elevation filtered point clouds at each angle;

[0107] Perform multi-angle data fusion on the regular grid elevation filtered point clouds at all angles to obtain DSM data for complex terrain. Considering the projection overlap caused by complex terrain undulation and multi-angle data acquisition, atomic operations are used during cross-thread calculation, so as to ensure the correctness and accuracy of the calculation results without reducing efficiency.

[0108] Second aspect:

[0109] Based on the above method for reconstructing DSM based on airborne multi-angle InSAR, the present invention also provides a system for reconstructing DSM based on airborne multi-angle InSAR, as Figure 7 shown, the DSM reconstruction system includes:

[0110] A data acquisition module, which is used for the complex terrain of the measurement area, plans data acquisition tasks at multiple angles based on the terrain undulation to obtain flight routes and radar parameters at multiple angles; based on the flight routes and radar parameters at multiple angles, perform radar detection on the measurement area at multiple angles to obtain SAR raw echo data at multiple angles;

[0111] A data processing module, which is used to process the SAR raw echo data at multiple angles by using a high-precision InSAR data processing method to obtain DSM data at multiple angles;

[0112] A data fusion module, which is used to perform fusion processing on the DSM data at multiple angles to obtain DSM data for complex terrain.

[0113] For the specific functions of each module in the DSM reconstruction system based on airborne multi-angle InSAR of the present invention, refer to the specific steps in the method for DSM reconstruction based on airborne multi-angle InSAR of the present invention, which will not be elaborated here.

[0114] Third aspect:

[0115] Based on the above method for DSM reconstruction based on airborne multi-angle InSAR, the present invention also provides a DSM reconstruction device based on airborne multi-angle InSAR. The DSM reconstruction device includes: a processor, a memory, and a computer program stored in the memory. When the computer program is executed by the processor, it implements the method for DSM reconstruction based on airborne multi-angle InSAR as described above.

[0116] In the method, system and device for DSM reconstruction based on airborne multi-angle InSAR of the present invention, terrain undulation is considered, and data acquisition tasks at multiple angles are planned, which can avoid invalid DSM data caused by shadows and layovers to the greatest extent. Then, through high-precision InSAR data processing, the high consistency of the DSM data accuracy at each angle is ensured; the present invention proposes to achieve high-precision reconstruction of DSM for complex terrain in the multi-angle InSAR system through fast multi-angle DSM data fusion processing.

[0117] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A DSM reconstruction method based on airborne multi-angle InSAR, characterized in that, Including: S1. For the complex terrain of the measurement area, plan data acquisition tasks at multiple angles based on the terrain undulation to obtain flight lines and radar parameters at multiple angles; Based on the flight lines and radar parameters at multiple angles, conduct radar detection of the measurement area at multiple angles to obtain SAR raw echo data at multiple angles; S2. Use a high-precision InSAR data processing method to process the SAR raw echo data at multiple angles to obtain DSM data at multiple angles; S3. Perform fusion processing on the DSM data at multiple angles to obtain DSM data for complex terrain.

2. The DSM reconstruction method based on airborne multi-angle InSAR according to claim 1, wherein The specific content of S1 is as follows: S11. For the complex terrain of the measurement area, plan multiple data acquisition flight lines based on multiple angles; S12. Taking the scope of the measurement area and the technical indicators of the InSAR radar as constraint conditions, statistically calculate the slope and aspect of the measurement area based on the rough-precision DSM data of the measurement area, and optimize the parameters of the data acquisition flight lines at each angle according to the slope and aspect of the measurement area to obtain the optimized parameters of the flight lines at each angle; S13. Taking the scope of the measurement area and the technical indicators of the InSAR radar as constraint conditions, optimize the InSAR radar parameters of the data acquisition flight lines at the corresponding angles according to the slope and aspect of the measurement area and the optimized parameters of the flight lines at each angle to obtain the optimized InSAR radar parameters at each angle; S14. Based on the rough-precision DSM data of the measurement area, as well as the optimized parameters of the flight lines and the optimized InSAR radar parameters at each angle, calculate the layover areas and shadow areas at each angle in the measurement area; S15. Determine whether the layover areas and shadow areas at each angle in the measurement area meet the preset requirements; if so, combine the optimized parameters of the flight lines and the optimized InSAR radar parameters at each angle as the flight lines and radar parameters at the corresponding angles; if not, return to S12 and execute in a loop until the layover areas and shadow areas at each angle in the measurement area meet the preset requirements, and combine the optimized parameters of the flight lines and the optimized InSAR radar parameters in the last loop at each angle as the flight lines and radar parameters at the corresponding angles; S16. Based on the flight lines and radar parameters at each angle, conduct radar detection of the measurement area at the corresponding angles to obtain SAR raw echo data at each angle.

3. The DSM reconstruction method based on airborne multi-angle InSAR according to claim 2, wherein The parameters of the data acquisition flight line include: flight line direction, flight line length, and flight line height; The InSAR radar parameters include: the side-looking direction, the down-looking angle, the signal bandwidth, the signal pulse width, and the sampling starting point of the InSAR radar.

4. The DSM reconstruction method based on airborne multi-angle InSAR according to claim 2, wherein, During the process of calculating the layover area, the determination condition for the layover area is: The included angle between the incident signal of the InSAR radar and the slope facing the oncoming slope in the measurement area is less than 90 degrees.

5. The DSM reconstruction method based on airborne multi-angle InSAR according to claim 2, characterized in that During the process of calculating the shadow area, the determination condition for the shadow area is: The signal incident angle of the InSAR radar is less than the slope of the back slope in the measurement area.

6. The DSM reconstruction method based on airborne multi-angle InSAR according to claim 2, characterized in that The specific content of S15 is Statistically calculate the total area of the measurement area to obtain the total area of the measurement area; statistically calculate the total area of all layover areas in the measurement area to obtain the total area of the layover area; statistically calculate the total area of all shadow areas in the measurement area to obtain the total area of the shadow area. Perform an addition operation on the total area of the layover area and the total area of the shadow area to obtain the total area of the invalid data area; divide the total area of the invalid data area by the total area of the measurement area to obtain the proportion of the total area of the invalid data area. Calculate the area of the largest isolated layover area among all layover areas to obtain the area of the largest isolated layover area. Calculate the area of the largest isolated shadow area among all shadow areas to obtain the area of the largest isolated shadow area. When the proportion of the total area of the invalid data area is less than or equal to the preset area proportion threshold, and the area of the largest isolated layover area is less than or equal to the preset invalid data area threshold, and the area of the largest isolated shadow area is less than or equal to the preset invalid data area threshold, it is determined that the layover area and the shadow area in the measurement area meet the preset requirements, and the combination of the flight path optimization parameters and the InSAR radar optimization parameters is used as the flight path and radar parameters. Otherwise, it is determined that the layover area and the shadow area in the measurement area do not meet the preset requirements, and the S12 is returned to execute in a loop until the layover area and the shadow area in the measurement area meet the preset requirements, and the combination of the flight path optimization parameters and the InSAR radar optimization parameters in the last loop is used as the flight path and radar parameters.

7. The DSM reconstruction method based on airborne multi-angle InSAR according to claim 1, characterized in that The specific content of S2 is as follows: Obtain the imaging parameters and internal calibration parameters at each angle, and correct the amplitude-phase error and system delay error of the SAR raw echo data at the corresponding angle through the internal calibration parameters at each angle; use the POS post-processing data at each angle to extract the motion compensation reference trajectory and process the Doppler parameters to realize the imaging processing of the SAR raw echo data at each angle, and obtain the SAR main image and SAR auxiliary image at each angle. According to the coordinate mapping relationship between the homologous points of the SAR main image and the SAR auxiliary image at each angle, resample the SAR auxiliary image at the corresponding angle to the same pixel grid as the SAR main image to realize the registration between the SAR auxiliary image and the SAR main image at each angle, and obtain the registered SAR auxiliary image and the coherence coefficient at each angle. Based on the coherence coefficient at each angle, perform image interference processing on the SAR main image and the registered SAR auxiliary image at the corresponding angle to obtain the interference phase at each angle. According to the InSAR working principle, perform flat-earth effect removal processing on the interference phase at each angle to obtain the flat-earth removed interference phase at each angle. Based on the coherence coefficient, use the SIGMA adaptive filtering method guided by the quality map to filter the flat-earth removed interference phase at each angle to obtain the filtered interference phase at each angle. Based on the coherence coefficient, use the quality map-guided fast phase unwrapping method to perform phase unwrapping on the filtered interference phase at each angle to obtain the unwrapped phase at each angle. Based on the coherence coefficient, filter the unwrapped phase at each angle to obtain the filtered unwrapped phase at each angle. Perform interference calibration on the filtered unwrapped phase at each angle to obtain the interference calibration parameters at each angle. Based on the working principle of airborne InSAR, parameter calibration and elevation calculation are carried out according to the imaging parameters, filtered and unwrapped phase, and interferometric calibration parameters at each angle to obtain DSM data at each angle.

8. The DSM reconstruction method based on airborne multi-angle InSAR according to claim 1, characterized in that The specific content of S3 is as follows: Based on the multi-threaded parallel computing resources of the GPU platform, the CUDA programming model is used to perform projection conversion on the DSM data at each angle to generate regular grid point clouds; among them, the regular grid point clouds include regular grid elevation point clouds, regular grid coherence coefficient point clouds, and regular grid interferometric phase point clouds; The gradient of the regular grid coherence coefficient point cloud and the regular grid interferometric phase point cloud at each angle is used to perform weighted filtering on the regular grid elevation point cloud at the corresponding angle to obtain the regular grid elevation filtered point cloud at each angle; The regular grid elevation filtered point clouds at all angles are subjected to multi-angle data fusion to obtain DSM data for complex terrain.

9. An airborne multi-angle InSAR-based DSM reconstruction system, characterized in that, It includes: A data acquisition module, which is used for the complex terrain of the measurement area, plans data acquisition tasks at multiple angles based on the terrain undulation to obtain flight routes and radar parameters at multiple angles; based on the flight routes and radar parameters at multiple angles, the measurement area is detected by radar at multiple angles to obtain SAR raw echo data at multiple angles; A data processing module, which is used to process the SAR raw echo data at multiple angles by using a high-precision InSAR data processing method to obtain DSM data at multiple angles; A data fusion module, which is used to perform fusion processing on the DSM data at multiple angles to obtain DSM data for complex terrain.

10. An airborne multi-angle InSAR-based DSM reconstruction device, characterized in that, It includes a processor, a memory, and a computer program stored in the memory. When the computer program is executed by the processor, it implements the DSM reconstruction method based on airborne multi-angle InSAR according to any one of claims 1 to 8.

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