Evaluation of Different GNSS Augmentation Methods for UAS-based Shoreline Mapping

The use of an unoccupied aircraft system (UAS) and structure-from-motion (SfM) photogrammetry for shoreline verification, feature identification, and topographic surveying in the coastal zone affords the possibility of reducing costs and improving safety. Traditional approaches rely on extensive ground control networks for improving absolute positioning accuracy, which greatly increases the effort required and presents logistical challenges along remote and dynamic sections of coastlines. In this study, the accuracy of UAS-SfM for shoreline mapping, without the aiding of ground control, is being investigated through field testing and data processing experiments based on different GNSS solutions. The study site consists of a wave dominated, sandy beach environment located on Mustang Island, TX, USA. GNSS methods investigated include real-time kinematic (RTK) corrections, post-processed kinematic (PPK) corrections using local and remote base stations, and precise point positioning (PPP). Multiple UAS platforms are evaluated and SfM accuracy results compared to ground control surveys conducted with a total station, RTK GNSS, and 3D laser scanning. Additionally, SfM processing workflows are evaluated across various SfM software based on the different GNSS approaches tested. Results of this project are anticipated to benefit and inform other UAS users within the coastal monitoring and surveying community.