This map presents historical coastal landcover change generated from optical satellite imagery in Landsat and Sentinel-2 constellations. Users can view landcover percentage change for sediment, water, and vegetation and estimated shoreline change for Instantaenous Waterline and Edge of Vegetation shoreline proxies within each hexagonal cell.
The initial national scale coastal classification is described in Collings et al., (2022), and a map-to-image change detection approach was used to estimate change between this classification and subsequent imagery. Google Earth Engine was used to preprocess and download imagery, via a service account. To correct estimated waterline position for tide, beach slope was acquired from Zenodo which was calculated by @kvos using CoastSat.slope. The NIWA tide API was used to acquire tide level.
Processing and results were calculated on a NeCTAR VM and updates are scheduled to check for new images and update the record monthly.