Guidelines for Bathymetric Mapping and Orthoimage Generation using sUAS and SfM, An Approach for Conducting Nearshore Coastal Mapping

The absence of accurate, contemporary, or detailed bathymetric data in nearshore coastal waters impedes coastal research, conservation, disaster response, planning, and management efforts. The use of small Unmanned Aircraft Systems (sUAS) and low cost RGB (red, blue, green) cameras, coupled with advanced photogrammetry methods, structure from motion (SfM), provides a portable, efficient, rapid-response, and cost-effective method to fill nearshore data gaps. The sUAS/SfM approach provides an alternative method to traditional nearshore collection techniques, and is one that can benefit a diverse user community. The digital elevation models (DEMs) and photomosaics that result from the sUAS-SfM approach can provide users access to data of unparalleled resolution, previously unavailable. This methodology works well in environments with clear water, low wave conditions, and distinct visible features on the seafloor. Areas with poor water clarity, high wave conditions, breaking waves, or homogeneous sandy bottoms, are not well suited for this acquisition and processing methodology. Additionally, it is recommended that the sUAS platform selected be capable of acquiring a high accuracy trajectory (e.g., Carrier phase global navigation satellite systems), in order to generate accurate data products.