測深光達波形與水深、底質關係觀察

Exploration on Waveforms of Bathymetric Lidar

林暐尊(Wei-Tsun Lin) ； 史天元(Tian-Yuan Shih) ； 張智安(Tee-Ann Teo)

《航測及遙測學刊》 16卷3期 (2012/08) Pp. 218-228

https://doi.org/10.6574/JPRS.2012.16(3).6

摘要

測深光達（Bathymetric Lidar）以近紅外光及綠光之雷射掃描方式進行水域之水深及水底地形量測，藉由偵測水面及水底之回波時間間距求得空間距離以達探測水深效果。本研究使用東沙及澎湖之AHAB HawkEye IIb掃描數據及Coastal Survey Studio（CSS）軟體進行數據分析，以水面定義、水質濁度、底質種類及地形影響各方面進行探討，比較項目包含水深、信噪比量化數據，以及搭配相機影像判識之底質種類等差異。實驗結果顯示，由於HawkEye IIb系統對綠光訊號之時變增益處理，水深對波形狀態影響不顯著；混濁水質造成水體中有較強散射訊號，淺水區水面及水底訊號間衰減現象較不顯著，而於深水區域甚至可能無法測得水底回訊。波形狀態呈現則與陸域光達類似，波形強度受反射面材質影響，且反射面幾何形態亦造成波形寬度改變。依本文探討CSS軟體成果對應接收波形，盼作為未來測深光達波形處理時回波偵測、點雲分類等作業之參考。

關鍵字

測深光達 ； 波形

並列摘要

Bathymetric Lidar uses near infrared and green band lasers to acquired the water depth and underwater topography. The spatial distance can be estimated from the return signals of the surface and the bottom of water. Dongsha and Penghu are the test areas. The test data are acquired by AHAB HawkEye IIb and processed by Coastal Survey Studio (CSS) software. This study analyses the surface definition, water turbidity and bottom topography. The quantitative analysis includes water depth, signal-to-noise ratio and types of sea bottom. The experiment indicates that depths affected by waveform appearances are not obvious due to the Time-varied Gain (TVG). The turbid water makes stronger volume backscatter and decreases the attenuation effect, even leads to the bottom echo undetectable with deeper water. Waveform appearance is varied with types of reflective material and geometry, as well as influencing the strength and pulse width, respectively. This study analyses the relationship between waveform acquired by HawkEye IIb and results processed by CSS software. The experimental results may provide some evidences for further processing such as bathymetric Lidar echo detection, point cloud classification, and others.

並列關鍵字

Bathymetric Lidar ； Waveform