Evaluating the 3D Integrity of Underwater Structure from Motion Workflows

Abstract Structure from motion (SfM) is an accessible and non‐intrusive method of three‐dimensional (3D) data capture popular for tropical coral reef surveying. In the north‐east Pacific Ocean, where there are many environmentally sensitive benthic organisms whose morphology and function are equally important, SfM surveys are less commonly studied. Temperate waters pose unique challenges to SfM workflows, which must be systematically unpacked to understand their impact on data quality and veracity. This uncertainty raises broader questions concerning SfM as a spatial data‐acquisition and ecological characterisation method in temperate waters, and whether a systematic workflow assessment reveals vital relationships between SfM implementation parameters, 3D data products and their implications for underwater SfM surveys. This paper, the second of two empirical assessments, reports on a series of wet‐lab and dryland tests quantifying the impact that temperate waters, underwater cameras, and photograph quantity and configuration have on SfM accuracy. These tests provided crucial accuracy benchmarks informing subsequent field‐based surveys and revealed that underwater SfM workflows can generate highly accurate 3D models in temperate waters.