WAVEFORM ANALYSIS TECHNIQUES IN AIRBORNE LASER SCANNING
WAVEFORM ANALYSIS TECHNIQUES IN AIRBORNE LASER SCANNING
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发表时间：
2007
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通讯作者：
W. Wagner;A. Roncat;T. Melzer;A. Ullrich
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作者：
W. Wagner;A. Roncat;T. Melzer;A. Ullrich
具有波形数字化能力的小型机载激光扫描仪越来越多。当后向散射回波波形复杂时，波形数字化特别有利，因为它允许选择调整到任务的处理算法。此外，波形数字化激光扫描仪还能全面描述物理测量过程。这打开了可能性，以获得后向散射截面，这是一个衡量电磁能量拦截和再辐射的对象。本文讨论了计算激光束沿着光路截面的方法。出于数据存储和处理的原因，一种实用的方法是将波形建模为从各个散射体反向散射的多个回波的总和。这种方法包括估计回波的数量，找到建模回波和测量波形之间的匹配，以及使用校准目标估计横截面。为了估计回波的数量和位置，测试了平均平方差函数（ASDF）方法，这是一种离散时间延迟估计技术。结果表明，ASDF是一种很有前途的方法，它似乎是受噪声的影响较小，比更传统的回波检测方法。
Small-footprint airborne laser scanners with waveform-digitising capabilities are becoming increasingly available. Waveformdigitising is particularly advantageous when the backscattered echo waveform is complex because it allows selecting processing algorithms adjusted to the task. In addition, waveform-digitising laser scanners depict the physical measurement process in its entire complexity. This opens the possibility to derive the backscatter cross section which is a measure of the electromagnetic energy intercepted and reradiated by objects. In this paper approaches for deriving the cross section along the laser ray path are discussed. For data storage and processing reasons a practical approach is to model the waveform as the sum of a number of echoes backscattered from individual scatterers. This approach involves estimating the number of echoes, finding a match between the modelled echoes and the measured waveform, and estimating the cross section using calibration targets. For estimating the number and position of echoes the Average Square Difference Function (ASDF) method, which is a discrete time delay estimation technique, is tested. The results show that ASDF is a promising approach which appears to be less affected by noise compared to more traditional echo detection methods.