The objective was to evaluate the feasibility of measuring bathymetry using airborne green LiDAR in long and variable river reaches (4 km or more), across three rivers with varying gradients, water depths and light penetration (3.5–10 m), using four alternative LiDAR sensors. The accuracy of green LiDAR data was compared to in situ measurements collected by stratified transect point sampling and Multibeam bathymetry. Factors potentially limiting the feasibility of green LIDAR in rivers were explored. If remote sensing signals were reflected by the riverbed, the sensors generally provided elevation data consistent with in situ elevation measurements, indicating high accuracy (±10 cm) across different hydraulic conditions. The loss of green LiDAR data was mainly a consequence of limited signal water penetration capability, that is, water clarity. Secchi depth was a proxy variable strongly associated with green LiDAR penetration capability across rivers. Data loss was low up to the Secchi depth but increased rapidly thereafter. Surface water turbulence (‘white water’) and dark riverbed vegetation also increased green LiDAR signal loss. Sensors with lower point density and therefore less spatial resolution had more signal strength and therefore penetrated deeper water. However, with increasing coverage of surface turbulence (‘white water’), the importance of high point density also increased. Signal power should be balanced with signal density (spatial resolution), depending on river characteristics and project objectives. We conclude that remote sensing green LiDAR bathymetry is a robust method that efficiently provides accurate elevation data across rivers with different hydraulic conditions and water depths.

中文翻译：

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评估河内测深测量方法：遥感绿色激光雷达提供受水渗透能力限制的高分辨率河床地形

目的是评估使用机载绿色激光雷达在长且多变的河段（4 公里或以上）、跨越具有不同坡度、水深和光穿透力（3.5-10 m）的三条河流，使用四种替代激光雷达测量水深的可行性传感器。将绿色激光雷达数据的准确性与分层样线点采样和多波束测深收集的原位测量结果进行比较。探讨了可能限制绿色激光雷达在河流中的可行性的因素。如果遥感信号由河床反射，传感器通常提供与现场高程测量一致的高程数据，表明在不同水力条件下具有较高的精度（±10厘米）。绿色激光雷达数据的丢失主要是由于信号水穿透能力（即水体透明度）有限的结果。Secchi 深度是与绿色激光雷达跨河流穿透能力密切相关的代理变量。直到 Secchi 深度，数据丢失率较低，但此后迅速增加。地表水湍流（“白水”）和深色河床植被也增加了绿色激光雷达信号的损失。点密度较低、空间分辨率较低的传感器信号强度较高，因此可以穿透更深的水域。然而，随着表面湍流（“白水”）覆盖范围的增加，高点密度的重要性也随之增加。信号功率应与信号密度（空间分辨率）相平衡，具体取决于河流特征和项目目标。我们的结论是，遥感绿色激光雷达测深是一种稳健的方法，可以有效地提供不同水力条件和水深的河流的准确高程数据。