Surface Reflectance Satellite Data
Surface Reflectance (SR) is reflectance corrected for atmospheric effects, giving an accurate representation of the Earth's surface properties. SR data underpins a range of remote-sensing analyses, from vegetation monitoring and land-use mapping to change detection and crop yield estimation.
Piksel provides five SR products from two main constellations: the Landsat family (USGS) and Sentinel-2 (ESA).
Product Comparison
| Product | Sensor | Resolution | Coverage | Revisit | Best for |
|---|---|---|---|---|---|
| Landsat 5 | TM | 30 m | Mar 1984 – Jun 2013 | 16 days | Historical analysis, 1984–2013 |
| Landsat 7 | ETM+ | 30 m | Apr 1999 – Jan 2024 | 16 days | Long-term time series (SLC-off after May 2003) |
| Landsat 8 | OLI | 30 m (15 m pan) | Mar 2013 – present | 16 days | Regular updates, consistent with L9 |
| Landsat 9 | OLI-2 | 30 m (15 m pan) | Oct 2021 – present | 16 days | 14-bit radiometry, paired with L8 |
| Sentinel-2 | MSI | 10–60 m | Jan 2017 – present | 5 days | Highest resolution, red-edge bands, precision agriculture |
Combining Landsat 8 + 9 provides an effective revisit time of 8 days. Adding Sentinel-2 allows the same area to be observed up to several times per week.
Choosing a Product
- Need a long historical record? — Use Landsat 5 for 1984–2013 or Landsat 7 for 1999–2024. Both products have 30 m resolution and are consistent with each other.
- Need the highest resolution? — Sentinel-2 provides 10 m pixels in the RGB and NIR bands.
- Need regular updates and a short revisit time? — Combine Landsat 8, Landsat 9, and Sentinel-2.
- Need red-edge bands for advanced vegetation analysis? — Sentinel-2 provides three red-edge bands (B5, B6, B7).
- Need surface temperature rather than reflectance? — See Surface Temperature.
About Surface Reflectance
Surface reflectance (BOA — bottom-of-atmosphere) differs from top-of-atmosphere reflectance (TOA — top-of-atmosphere) because it has been corrected for:
- Scattering by aerosols and air molecules
- Absorption by water vapour and other atmospheric gases
- Adjacency effects from surrounding objects
Each product uses a different correction algorithm: LEDAPS for Landsat 5/7, LaSRC for Landsat 8/9, and Sen2Cor for Sentinel-2. These algorithm differences produce small variations between products that need to be considered when combining cross-sensor datasets for time-series analysis.