Close range photogrammetry in the survey of the coastal area geoecological conditions (on the example of Portugal)

Abstract

Close range digital photogrammetry, which involves the application of unmanned aerial vehicle (UAV), has been used in a growing number of diverse applications across different scientific disciplines. Our objective was to use the mentioned method in the survey of the contemporary geoecological conditions of the coastal area on the example of Portuguese northwest coastal zone. The coastal zone can be subdivided into two geomorphological sectors: Sector 1, between the Minho River and the town of Espinho, where the coastal segments consist of estuaries, sandy and shingle beaches with rocky outcrops, and Holocene dune systems. The estuaries and the foredunes in particular are very degraded by human activities; and Sector 2, between Espinho and the Mondego Cape, where coastal lagoons and Holocene dune systems occur. We chose two beaches for surveying – Aguçadoura and Ramalha to which the drone swinglet CAM took the photos. We used the ground control software eMotion 2 to plan the flights over the study area and controlled the drone’s trajectory during flight. After processing the obtained images in the program of AgisoftPhotoscanPro, we generated the 2D orthophotos and 3D digital elevation models (DEM) of the research sections. At this stage of study we derived the above product without using the ground control points, or we used only the camera GPS data. Based on these models the compilation of the large-scale maps of high resolution (1cm-5cm) will be possible in the GISs for monitoring and management of the geoecological state of the mentioned beaches in case to precise the x, y and z values of the models with the geodetic device of Differential GPSs in the selected ground control points (GCP).