机载激光测深系统强度数据AGC补偿异常区域识别及改正

机载激光测深系统（Airborne Laser Bathymetry，ALB）因集成了具有独特水体穿透能力的绿波段（532 nm）而被广泛用于水深测量。除地形数据外，ALB还记录了地物目标的辐射特性（后向散射强度），可用于条带配准、海底底质分类和几何建模。然而，由于自动增益控制（Automatic Gain Control，AGC）设计局限，增益值调整存在延缓，对于裸露岩石、水域等高返回、低返回目标较多的海岛海岸带区域，强度补偿异常问题格外突出。针对该问题本文设计了一种基于双向移动的局部加权强度改正方法，提出索引共享机制辅以地形信息实现有效强度数据精确提取；以扫描周期为依据进行扫描线分割，通过柯尔莫可洛夫−斯米洛夫检验进行强度补偿异常区识别；通过对邻近扫描线和邻域强度联合加权进行强度改正，保证强度细节的同时较好地消除与邻域强度偏差，独特的双向移动策略能有效削弱改正不足积累造成的强度改正精度下降问题。实验证明该方法能有效解决AGC补偿异常问题，相较于改正前，改正后的强度数据平均绝对百分比误差降低了约0.27，均方根误差下降了约693，异常区强度与邻域强度偏差控制在26 DN（Digital Number）以内，得到高质量强度图像。

Identification and correction of airborne laser bathymetry intensity data in AGC compensated abnormal zone

Airborne Laser Bathymetry (ALB) as an established surveying procedure is certainly operated in blue-green region (532 nm) for penetrating the water column to collect depth. Alongside geometric information accepted widely, ALB typically record the radiometric properties (backscattering intensity) about sensed targets and assist with accurate strips registration, fine ground (sediment) cover classification, and advanced geometric modelling. However, due to the design limitations of Automatic Gain Control (AGC), there is a delay in gain value adjustment, particularly prominent in island and coastal areas with more high-return and low-return targets such as exposed rocks and water, which throws the issue of intensity compensation abnormality into stark relief. In response to this issue, a local weighted intensity correction method based on bidirectional movement is designed. Firstly, effective intensity is extracted by index sharing and elevation information. Then, the emission angles are used to divide the scan line and serve as the judgment unit, and the Kolmogorov-Smirnov test is used to identify the abnormal area. Finally, intensity correction is performed by joint weighting of adjacent scan lines and neighborhood intensity, where the joint weighting can ensure the intensity details while eliminating the deviation from the neighborhood intensity. In addition, a unique bidirectional moving strategy is introduced to weaken the decline of strength correction accuracy caused by insufficient correction accumulation. Experiments have illustrated that this approach can effectively solve the AGC compensation anomaly problem, and compared to the pre-correction, the average absolute percentage error of the corrected intensity data decreased by about 0.27, the root mean square error decreased by about 693, and the intensity deviation of the abnormal area was controlled within 26 DN (Digital Number), thus obtaining a high-quality intensity image.