Three-dimensional Reconstruction Method for Detecting Small Targets within Walls Based on a Multistage Cascade U-Net Approach Using Ground Penetrating Radars
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摘要: 探地雷达(GPR)在对掩埋目标的探测中发挥着至关重要的作用,尤其在墙体内小目标检测及重建方面。由于墙体结构及材质的复杂性,墙内小目标精准重建面临极大挑战。针对墙内小目标重建难题,该文提出了一种多阶段级联U-Net方法,用于墙内小目标的三维重建。首先,通过蒙特卡罗抽样生成符合级配要求的物理三维骨料散射模型,构建了复杂墙体场景的高分辨率探测模型和数据集,以提高模拟的真实性和准确性;其次,多阶段网络结构的设计能够有效抑制C扫描数据中的噪声和非均质杂波,从而提升信号质量;最后,预处理后的数据用于重建小目标三维分布。此外,该文还引入了一种自适应多尺度模块和级联网络训练策略,优化了复杂场景中小目标信息的拟合性能。通过模拟与实测数据的对比,验证所提方法的有效性和泛化能力。相比现有技术,该方法成功重建了三维墙体内小目标,显著提高了峰值信噪比,为小目标的准确探测提供了重要技术支持。Abstract: Ground Penetrating radars (GPR) are essential for detecting buried targets in civilian and military applications, especially given the increasing demand for detecting and imaging small targets within walls. The complex structures and materials of walls pose substantial challenges for precisely reconstructing small targets. To address this issue, this study proposes a multistage cascaded U-Net approach for the three-dimensional reconstruction of small targets within walls. First, we developed a high-resolution detection model and a dataset tailored to handle complex wall scenes. Thereafter, using the Monte Carlo sampling method, we sampled aggregate particle sizes to create a physical three-dimensional aggregate scattering model that satisfies grading requirements, thus enhancing the realism and accuracy of the simulated scenes. Our multistage network design effectively suppresses noise and inhomogeneous clutter in C-scan data, thereby improving signal quality. The preprocessed data are then fed into subsequent network stages to reconstruct the distribution of three-dimensional reconstruction values. In addition, we proposed an adaptive multiscale module and a cascaded network training strategy to better fit small target information in complex scenes. Through comparisons with simulated and measured data, we confirmed the effectiveness and generalizability of our method. Unlike existing techniques, our approach successfully reconstructs small targets within three-dimensional walls, thereby considerably enhancing the peak signal-to-noise ratio and providing critical technical support for accurately detecting small targets within walls.
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表 1 仿真数据集预设置参数
Table 1. Simulation data set preset parameters
目标参数 设置范围 数量 1~2 形状 圆柱体和长方体 位置 随机 介质类型 金属 掩埋深度 40~60 mm 圆柱体厚度 10~20 mm 圆柱体半径 10~20 mm 长方体长、宽、高 15~30 mm 表 2 不同方法下的降噪评估指标对比
Table 2. Comparison of denoising evaluation indicators under different methods
方法 骨料配级比(%) 骨料配级比(%) 骨料配级比(%) 2 4 6 8 10 2 4 6 8 10 2 4 6 8 10 PSNR(dB)↑ RMSE↓ MAE↓ RNMF 33.21 34.43 33.61 33.35 33.94 0.5355 0.4913 0.5836 0.4581 0.5636 0.0929 0.0859 0.0937 0.0881 0.0905 RPCA 38.22 39.05 38.49 38.36 38.93 0.2992 0.2881 0.3373 0.2562 0.3158 0.0761 0.0709 0.0773 0.0722 0.0741 3DInvNet[24] 35.92 37.13 36.23 35.90 36.52 0.3931 0.3611 0.4351 0.3383 0.4199 0.0429 0.0375 0.0432 0.0412 0.0418 所提方法 56.18 56.90 55.04 53.01 54.62 0.0368 0.0357 0.0472 0.0476 0.0495 0.0183 0.0168 0.0196 0.0201 0.0205 注:加粗数值为 表 3 不同方法下的重建评估指标对比
Table 3. Comparison of reconstruction evaluation indicators under different methods
指标 3DInvNet[24] 所提方法 PSNR(dB)↑ 34.78 52.17 SSIM↑ 0.9969 0.9986 RMSE↓ 0.1629 0.0074 MAE↓ 0.0092 0.0071 OR 0 0.9241 AR 0 4.0985 均值 – 0.0001 17.5678 表 4 所提方法在不同测试集上的评估指标
Table 4. Evaluation indicators of the proposed scheme on different test sets
测试集 PSNR↑/(dB) SSIM↑ RMSE↓ MAE↓ 改变
骨料模型48.63 0.9974 0.0081 0.0115 增加
旋转目标46.74 0.9978 0.0209 0.0101 增加
目标数量36.83 0.9945 0.0983 0.0199 增加
骨料含量43.77 0.9962 0.0309 0.1443 表 5 所提方法在不同背景材质下的重建指标对比
Table 5. Comparison of reconstruction indicators of the proposed scheme under different background materials
背景介电常数值 PSNR(dB)↑ SSIM↑ RMSE↓ MAE↓ 5.50 42.15 0.9945 0.0338 0.0161 5.75 45.70 0.9969 0.0157 0.0124 6.00 48.63 0.9974 0.0086 0.0115 6.25 48.14 0.9968 0.0086 0.0123 6.50 45.10 0.9949 0.0159 0.0151 表 6 消融实验
Table 6. Ablation experiment
实验 PSNR(dB)↑ SSIM↑ RMSE↓ MAE↓ (1) 44.85 0.9976 0.0219 0.0108 (2) 50.34 0.9976 0.0129 0.0079 (3) 31.07 0.6391 0.3735 0.2388 (4) 51.29 0.9981 0.0081 0.0097 (5) 52.17 0.9986 0.0074 0.0071 注:加粗数值 表 7 所提方法在实测算例的重建评估指标对比
Table 7. Comparison of reconstruction evaluation indicators of the proposed method in the measured example
指标 数值 PSNR(dB)↑ 36.49 SSIM↑ 0.9805 RMSE↓ 0.1033 MAE↓ 0.04155 OR 0.5708 AR 4.5737 均值 13.5055 -
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