Photogrammetric Survey of an Intertidal Area: A Case Study in NW Spain

For years, bathymetry technique has been employed to obtain georeferenced data of the depths of the water using an echo sounder on board. This led to some problems in shallow water because it requires a shallow draft boat, but thanks to technological advances, in recent years, Unmanned Aerial Vehicles (UAVs) are used for a wide variety of applications, including bathymetry in these context. There are recent works that propose its use through multispectral data or photographic images. These methods allow much more complete and precise work to be carried out, since data collection could not be possible through traditional methodology. In the present work, a combination of the data obtained by photogrammetric survey with UAV is made for the zones that are characterized by a shallower depth and bathymetric survey with a low-cost sounder (fishing sounder) for the deeper zones. From the combination of both methods, the bathymetry of the intertidal zone of the Pontedeume estuary (Spain) is obtained. In this way, Digital Terrain Model (DTM) and bathymetry are performed, which provides complete information of the morphological characteristics created by sea currents.