Accuracy and effectiveness of low cost UASs and open source photogrammetric software for foredunes mapping

The recent use and availability of small and low cost Unmanned Aerial Systems (UAS) and the development of Open Source Photogrammetric (OSP) software opens new opportunities for their intensive use in topographic monitoring of foredune dynamics. This study assesses the accuracy and effectiveness of high resolution Digital Surface Models (DSM) generated by the combined use of low-altitude UAS imagery and OSP software. The Photogrammetric Workflow (PW) has been optimized to address the use an action camera and non-autonomous flight mode. To evaluate the accuracy of the DSMs derived from dense matching of UAS imagery we use a reference DSM obtained by a Terrestrial Laser Scanner in the same survey period. Moreover, we use robust statistical indicators for assessing the vertical accuracy of both DSMs: the raw DSM and the denoised DSM. The results shows that a detailed UAS-based DSM with a spatial resolution of 5 cm and vertical accuracy of 10 cm (robust root mean square error) can be obtained by using the proposed PW. The results also suggest that this low cost technology can be used effectively for 3D mapping of foredunes.