Sentinel 1 -SAR
The detection of the waterline using Synthetic Aperture Radar (SAR) images is based on the exploitation of the Interferometric Wide Swath images at High Resolution. Water and land are classified using a histogram thresholding technique and the resulting edge is vectorised.
Sentinel 2 -VNIR
Waterlines can be detected in the Visible and Near InfraRed (VNIR) with Sentinel 2 using a combination of bands to accentuate the contrasting spectral features of water and land. Using locally adaptive thresholds along the coastline, the land and sea can be discretely classified, and a waterline drawn along the boundary between these two features. Due to the locally adaptive approach, this process aims to produce a waterline that is highly accurate across all environments including beaches, cliffs, ports & estuaries.
For both sensors, these vectorised waterlines are then contextualised with local tidal data in order to allow for timeseries analysis of changing waterlines at similar tidal heights.