Topobathymetric DEMs of Short Prong marsh and tidal flat in Hog Island Bay, VA 2022-2023

Seamless DEMs of the marsh edge and tidal flat at Short Prong in 2022 and 2023 were created using a combination of aerial photogrammetry and boat-mounted single-beam echosounding. Aerial photogrammetry surveys of the subaerial intertidal flat and marsh edge were completed during low tide using a DJI Phantom 4 RTK drone. Positioning was determined using six surveyed ground control points and drone on-board RTK. During high tide, a single beam echosounder was used to survey six cross-shore transects of the subtidal and one alongshore transect near the marsh edge. The same flight plan and echosounding survey path was used both years, with surveys taking place on 7/19/22 and 7/11/23. Photogrammetric data was processed in Agisoft Metashape to produce a DEM and a photomosaic. Echosounding data was processed in Hydromagic and interpolated using the natural neighbor method in GIS. Overlap of survey extent between photogrammetric and echosounding DEMs were stitched together in GIS to create seamless DEMs with a cellsize of 3 cm from the lower elevations of the marsh platform into the subtidal flat for 2022 and 2023.