A cost-effective, open-source laboratory system for 3D photogrammetric analysis of corals

Three-dimensional photogrammetry is a method used to measure 3D reconstructions created from 2D images. The precision of this method makes it widely used for studying ecosystem engineers such as corals. Although photogrammetry has been used to study both tropical and cold-water corals in situ, very few studies, with certain limitations including potential coral stress or low replicability, use photogrammetry to study corals in aquaria. For accurate 3D photogrammetric measurements of corals under laboratory conditions, we present the “Coruña 3D system” and the two prototypes that served as input for the development of the final setup. The “Coruña 3D system” is presented as a publicly accessible cost-effective setup used to obtain a complete set of images of a coral in an aquarium and create accurate 3D reconstructions. Using photogrammetry to study corals in aquaria enables the measurement and monitoring of different variables over both, short and long periods of time. The effectiveness of the system was assessed with a total of 120 3D reconstructions of cold-water corals. The system has resulted in a highly accurate tool, creating 3D reconstructions with a total scale error of 0.048 ± 0.079 mm (mean ± SD). Moreover, this open-source, cost-effective (<3000 €) system provided precise results overcoming the limitations of previous prototypes and mechanisms used in other studies. The adaptability of the "Coruña 3D system" according to the needs of the study makes it a versatile and useful tool to measure corals as well as other benthic marine species.