3D photogrammetric surveys on coral reefs in the Maldives.

The global increase in seawater temperature is causing irreparable damages to coral reefs all over the world. Frequency of coral bleaching episodes and mass mortality is increasing and coral reefs have not enough time to recover after these impacts. The present study concerns this phenomenon in the context of the Maldives. In this scenario, monitoring activities are very important to check the health of coral reefs, and the adoption of specific parameters such as reef rugosity and accretion of corals provides important measures of the ability of reefs to recover after bleaching. Moreover, the use of photogrammetry allows speeding up the on-site measurements, enlarging the scale and the reliability. The input data are the images traditionally taken by operators for visual analysis, paying attention to the achievement of photogrammetric principles.