Bathymetry is the measurement of water depth and seafloor features. This bathymetry product was developed by the Allen Coral Atlas team using satellite data and advanced algorithms to estimate shallow water depth across coastal regions.
Data Properties
- Resolution: 10 meters
- Data Source: Sentinel-2 surface reflectance imagery processed via Google Earth Engine (GEE)
- Timeframe: 12 months of satellite observations
- Image Quality: Only clear, low-turbidity, low-cloud satellite images are used
- Image Composition: A median mosaic is generated from multiple images to reduce anomalies
- Supplementary Data: Where Sentinel-2 data is insufficient, Landsat-8 and Planet Dove imagery are added to complete the bathymetry composite
Bathymetry Mapping Method
This bathymetry mapping method is an automated adaptation of the single-scene adaptive bathymetry algorithm by Li et al. (2019), optimized for clean mosaics generated in GEE.
Key Steps in the Process:
-
Surface Reflectance Conversion
Convert surface reflectance (ρ(λ)) into Remote Sensing Reflectance (Rrs) values. -
Below-Surface Correction
Adjust the Rrs values to remove the air-water surface effect, resulting in below-surface reflectance (r-rs(λ)). -
Depth Estimation
Use the attenuation difference between blue and green bands to estimate shallow water bathymetry. -
Parameter Calculation (M0 and M1)
Estimate these constants using a fixed Chlorophyll-a (Chl-a) value representative of clean offshore waters.- This Chl-a value is the global average derived from 26 clean-water sites using the same GEE mosaic dataset.