Abstract
Due to both natural and anthropogenic causes the coastal primary sand dunes, keeps changing dynamically and
continuously their shape, position and extend over time. In this paper we use a case study to show how we monitor the
Portuguese coast, between the period 2000 to 2014, using free available multi-temporal Landsat imagery (ETM+ and
OLI sensors). First, all the multispectral images are panshaperned to meet the 15 meters spatial resolution of the
panchromatic images. Second, using the Modification of Normalized Difference Water Index (MNDWI) and kmeans
clustering method we extract the raster shoreline for each image acquisition time. Third, each raster shoreline is
smoothed and vectorized using a penalized least square method. Fourth, using an image composed by five synthetic
bands and an unsupervised classification method we extract the primary sand dunes. Finally, the visual comparison of the
thematic primary sand dunes maps shows that an effective monitoring system can be implemented easily using free
available remote sensing imagery data and open source software (QGIS and Orfeo toolbox).
