Key Points

Exercises: NDVI Analysis with Sentinel-2 Imagery

  • NDVI uses the ratio of near-infrared and red reflectance to quantify vegetation health and density.
  • Sentinel-2 Bands 4 (Red) and 8 (NIR) are the inputs for NDVI calculation in QGIS.
  • Refer to this Multispectral Band Combinations website here to learn what the function of each combination is!
  • The Raster Calculator applies the NDVI formula on a per-pixel basis across the entire image.
  • Thoughtful color symbology (red → yellow → green) makes NDVI results immediately interpretable.
  • Comparing NDVI output against a satellite basemap helps validate your interpretation of the results.

Exercises: Flood Analysis with False Color Composites and NDWI

  • False color composites remap spectral bands to RGB channels, making vegetation (red), water (dark blue), and bare soil (grey/white) visually distinct.
  • FCC is a quick visual tool but struggles with muddy or shallow floodwater that appears similar to bare soil.
  • NDWI uses the ratio of green and near-infrared reflectance to isolate water features, providing a more reliable delineation of flood extent.
  • Overlaying NDWI on an FCC combines the strengths of both methods — spectral precision from NDWI and spatial context from the FCC.