Using optical satellite and aerial imagery for automatic coastline mapping

The continuous availability and rapid accessibility to multispectral data from satellite platforms within the Copernicus Programme represents a great opportunity for users in different fields of applications as: agriculture, observation of coastal zones, monitoring land cover change. The aim of this paper is to identify a suitable method to map coastline using Sentinel-2 optical satellite image. The method provides the use of two indexes developed in remote sensing field for water environment: NDWI (Normalized difference water index) and MNDWI (Modified Normalized difference water index). Starting from the construction of maps of these indexes and, identifying appropriate threshold values, it has been possible to extrapolate the coastline. The coastlines derived from the use of the NDWI and MNDWI index were compared with a coastline obtained from the photointerpretation of a very high resolution orthophoto obtained through photogrammetric techniques. The results show that it is possible to map the coastline automatically and quickly with an intrinsic accuracy close to the geometric resolution bands of Sentinel-2 satellite images.