水體性質對於空載測深光達回訊影響及分析

The influence of different water condition on the returned signal of Airborne LiDAR Bathymetry(ALB)

鄭卉儀(Huei-Yi Cheng)

指導教授 ： 趙鍵哲

國立臺灣大學/工學院/土木工程學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.01152

摘要

空載測深光達系統原理主要利用雷射光脈衝(laser pulse)入射水體及接收回訊，並從回訊波形來界定水面及水底回訊時間，進一步解算水深。其解算水深原理，考量光入射水體折射的影響，但在實際環境中，雷射光入射水體會受環境的影響，水面、水體及水底狀態的變動都會影響雷射光路徑，進而影響最終接收到的回訊波形，導致在解算水深時會因為所引用的理論與實際狀況有所差異，造成量測水深的誤差。為掌握實際環境的變動對於空載測深光達量測品質的影響，本研究藉由利用水體光學參數(固有光學性質)及蒙地卡羅法模擬雷射光入射實際環境狀態的回訊，並從調變環境因子, 包括不同混濁程度與具有不同光活性物質成份的水體，以及調整設備因子(雷射光入射角及儲存能量解析度)，進而分析及探討這些因子的變化對於回訊解算及水深量測成果的影響。
從實驗成果來看，在越混濁的水體狀態，隨深度增加誤差會增加的越快；而在不同光學活性物質影響的測試中，從量測的品質來看，葉綠素的影響比無機懸浮顆粒顯著；提升時間解析度及在15~22度的入射角範圍內採用較小的入射角量測則均有助於提升量測成果。

關鍵字

空載測深光達 ； 蒙地卡羅法 ； 回訊波形 ； 水體光學性質

並列摘要

Airborne LiDAR bathymetry systems (ALB) fire laser pulses and receive returned waveforms to detect water bottom and surface, thus determining the water depth. Received waveforms may be influenced by hardware configurations, water surface condition, and water content. The quality of water-depth measurement is confined to the received waveforms and the algorithms used to decompose the waveforms and determine the water depth.
This study aims at generating and analyzing the waveforms by taking hardware, software components and water surface and content into full consideration. The simulated waveforms can be made by tuning the instrumental, geometric, and environmental factors influential to the determination of the water depth. The Monte Carlo method is employed to govern the events of transmission, scattering, absorption, and reflection on both geometric and radiometric intersections in relation to the confronted water content. The main contribution of this research is to quantitatively evaluate how the measured water depth quality is affected by different water condition and instrumental setting. Thus the optical properties of water in various content can be better appreciated and well treated when carrying out water depth measurement through ALB.

並列關鍵字

Airborne LiDAR Bathymetry ； Monte Carlo method ； returned waveform ； the optical properties of water

參考文獻

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