CORRECTING ATTENUATION EFFECTS CAUSED BY INTERACTIONS IN THE FOREST CANOPY IN FULL-WAVEFORM AIRBORNE LASER SCANNER DATA
CORRECTING ATTENUATION EFFECTS CAUSED BY INTERACTIONS IN THE FOREST CANOPY IN FULL-WAVEFORM AIRBORNE LASER SCANNER DATA
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DOI：
10.5194/isprsarchives-xl-3-273-2014
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发表时间：
2014-08
期刊：
影响因子：
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通讯作者：
K. Richter;N. Stelling;H. Maas
中科院分区：
文献类型：
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作者：
K. Richter;N. Stelling;H. Maas
抽象的。全波形机载激光扫描为各种林业应用提供了巨大的潜力。特别是需要有关下部冠层部分垂直结构信息的应用，可以从波形数据中包含的大量信息中受益。为了推导垂直森林冠层结构，开发合适的基于体素的数据分析方法很简单。除了提取额外的 3D 点之外，直接从数字化波形中导出体素属性也是非常有前途的。为此，必须将差分反向散射截面投影到笛卡尔体素结构中。因此，体素条目表示横截面的幅度，并且可以解释为脉冲反射物质的量的局部测量。然而，每个激光回波脉冲的“历史”特征是由牙冠较高区域的反射引起的衰减效应。因此，冠层内接收到的波形信号的幅度低于在没有先前冠层结构相互作用的情况下观察到的相同结构的幅度（Romanczyk 等人，2012）。如果生物物理结构是根据原始波形数据确定的，则冠层下部的材料因此代表性不足。为了实现辐射测量正确的体素空间表示，必须补偿由激光脉冲穿过冠层的路径上的部分反射引起的信号强度损失。在本文中，我们提出了一种校正每个记录样本的波形的积分方法。该过程的基本思想是增强冠层较低部分中脉冲强度部分的波形强度值，这些脉冲强度已在冠层较高部分中反射（并因此被阻挡）。本文将讨论所开发的校正方法，并展示使用合成数据和真实世界数据进行验证的结果。
Abstract. Full-waveform airborne laser scanning offers a great potential for various forestry applications. Especially applications requiring information on the vertical structure of the lower canopy parts benefit from the great amount of information contained in waveform data. To enable the derivation of vertical forest canopy structure, the development of suitable voxel based data analysis methods is straightforward. Beyond extracting additional 3D points, it is very promising to derive the voxel attributes from the digitized waveform directly. For this purpose, the differential backscatter cross sections have to be projected into a Cartesian voxel structure. Thereby the voxel entries represent amplitudes of the cross section and can be interpreted as a local measure for the amount of pulse reflecting matter. However, the "history" of each laser echo pulse is characterized by attenuation effects caused by reflections in higher regions of the crown. As a result, the received waveform signals within the canopy have a lower amplitude than it would be observed for an identical structure without the previous canopy structure interactions (Romanczyk et al., 2012). If the biophysical structure is determined from the raw waveform data, material in the lower parts of the canopy is thus under-represented. To achieve a radiometrically correct voxel space representation the loss of signal strength caused by partial reflections on the path of a laser pulse through the canopy has to be compensated. In this paper, we present an integral approach correcting the waveform at each recorded sample. The basic idea of the procedure is to enhance the waveform intensity values in lower parts of the canopy for portions of the pulse intensity, which have been reflected (and thus blocked) in higher parts of the canopy. The paper will discuss the developed correction method and show results from a validation both with synthetic and real world data.