 Tidal flats provide important habitats for marine life, protecting against storm surge and rising sea levels. However, due to the difficulty in mapping these areas on a large scale, their global status and distribution remains unknown. This paper presents a new method for mapping tidal flats over large areas, which was tested in three countries along the East Asian coast. The method uses Landsat satellite imagery to generate tide height predictions, then select suitable images taken during the upper and lower 10% of the tidal range. These images are then converted into a land slash water classification image based on the normalized difference water index, NDWI, and the high tide image is subtracted from the low tide image to create a map of the tidal flat. The resultant map covers 86.8% of the coastline studied, with an accuracy of greater than 85%. This method can be used to monitor coastal morphology and inform coastal adaptation measures for sea level rise, as well as to monitor coastal habitat loss and develop ecosystem-based coastal conservation measures. This article was authored by Richard A. Fuller, Robert S. Clemens, Stuart R. Finn, and others. We are article.tv, links in the description below.