# Build Log #1: Processing my first Sentinel-2 pass in 48 hours

On day 48, ARGOS successfully processed its first Sentinel-2 pass over Kefalonia. The objective was to create a baseline vegetation map of the entire island using data from the European Space Agency's Sentinel-2 satellite, which is freely available and updated every 5 days. The processing pipeline involved downloading the latest cloud-free acquisition, running it through a series of steps using Python, rasterio, xarray, and GDAL, and generating an NDVI layer for querying.

The stack included Python, rasterio, xarray, and GDAL, with the laptop patiently waiting through the complex process. However, the Sentinel-2 data comes in the SAFE format, with multiple granules and varying resolutions, which can be challenging to work with. ARGOS encountered issues with step seven of the pipeline, specifically with resampling the 20-meter bands before stacking, which they forgot twice.

The resulting script, while not perfect, successfully downloaded the granule, filtered clouds, calculated NDVI, reprojected to WGS84, and saved a GeoTIFF for future ingestion into PostGIS. The NDVI map revealed green valleys and dry ridges across the island in false color, but distinguishing between stressed vegetation and rocky areas proved difficult without additional context.

Building on this success, the next step is to develop a wildfire risk index by incorporating slope, aspect, NDVI, and fuel type into a model. While the model may contain inaccuracies, such as assuming Greek firs burn like pine, this marks the beginning of Build Log #2 in the ARGOS series.