*2.2. Data Acquisition*

The study is based on a time series of images of Bora Bora obtained through vertical aerial photographs taken from a plane, provided by the Urbanism service of French Polynesia (1955, 1977, 1987, and 1999) and satellite imagery extracted from Google Earth (2006, 2010, 2019), as detailed in Table 1. These dates were selected for their negligible or absent cloud cover. The satellite imagery was extracted at very high spatial resolution (<0.5 m) from Google Earth following the method from [16]; by adjusting the eye altitude to match the satellite spatial resolution, putting the nadir at 90◦, and positioning the view northward, over 60 images of the island were saved at maximum resolution for each date, with an overlap of around 30% between each subsequent image; these images were then assembled into orthomosaics similarly to the aerial images taken from a plane (see Section 2.3.1. Image preparation). Furthermore, a ground-based survey of the coastal typology was performed in 2019 using a GPS, by walking and sailing around the island and recording the location of different coastal types (similar methodology to [3]).


**Table 1.** Year, type of image, and spatial resolution of the time series of images of Bora Bora.
