珊瑚礁立體結構的量化與分析

Quantification and Analysis of 3D Structure of Coral Reefs

珊瑚礁的結構複雜度與其生態功能和生物多樣性息息相關，也是珊瑚礁健康狀態的代表性指標。然而，傳統方法很難客觀且有效率的對珊瑚礁的立體結構進行調查和評估；近年來興起的運動恢復結構（Structure from Motion, SfM）技術，是基於影像的低成本方法，能產生毫米等級的珊瑚礁三維模型。本文旨在介紹運用SfM方法於水下調查的作業流程及量化分析方法，並以基隆潮境和恆春萬里桐的珊瑚礁調查與三維建模為例，結果顯示能區分不同珊瑚群體及礁體的結構複雜度，用於評估人為擾動的影響。此外，也可以利用空拍機拍攝大範圍的礁體結構，或在實驗室中進行高解析度的珊瑚體影像拍攝，產生的三維模型可用於量化分析，也可應用於各種展示和科普教育。未來隨著資料的累積與硬體的進步，在海洋環境調查、生態保育和監測上將有很大的發展潛力。

The structural complexity of coral reefs which is essential for maintaining their high biodiversity and ecosystem functions can be a good indicator for assessing their healthy status. However, it is very difficult to quantify the structural complexity of coral reefs efficiently by traditional methods. Recently, the Structure from Motion (SfM), a low-cost photogrammetric method, has been increasingly applied to generate 3D models of coral reefs with high resolutions. Herein we introduce the standard protocols of applying SfM in underwater survey and quantitative analysis at Chaojing and Wanlitong reefs. The results of 3D models reveal the differences in structural complexity of benthic features and can be used to assess the impacts of marine activities on coral reefs. Besides, drones can also be used to survey the structural complexity of coral reefs in a larger area. In a smaller scale, photographs of a coral colony taken in lab or field can be used to generate 3D models in high resolutions. The 3D models can be used not only for quantitative analysis but also for public education and exhibitions. With the improvement of hardware and data accumulation in the future, the SfM methods will have high potential in marine ecological survey, ecosystem monitoring and conservation,