The accuracy of 3D structure-from-motion models for assessing underwater coral health

Abstract

A fundamental problem with using human observations in marine ecology is that it is often fallible. This study monitored coral to compare the accuracy of traditional visual surveying and 3D structure-from-motion models in assessing coral health. In a pilot study, objects of known dimensions were rendered underwater to assess the accuracy of the 3D models; between the X-Y and Z dimensions accuracies of 93 ±0.09% (mean ±SD) and 93 ±0.04% were observed, respectively. Following this, two surveyors monitored three individual coral colonies over five months at La Mer (Dubai) for the following visual parameters; live, dead and bleached coral. Significant differences were detected amongst surveyors for these parameters only when traditional surveying was implemented. However, 3D modelling had a significant post-processing time. Nonetheless, results suggest that 3D modelling is a more accurate and consistent tool between surveyors over time for monitoring coral colonies. The potential for such technology to be up-scaled to capture complete 3D-coral reefs could allow researchers to more accurately explore long-term changes to these significant ecosystems.