Processing

Surface reflectance (and atmospheric correction)

Converts raw sensor counts into the actual fraction of light reflected by the ground — required for any quantitative or multi-date work.

Fig. 1 Surface reflectance is what the ground actually reflects. The raw sensor measurement is top-of-atmosphere (TOA) reflectance — the composite of surface reflectance, atmospheric scattering and absorption, and sun angle geometry. Atmospheric correction inverts the atmospheric contribution to recover surface reflectance.

Raw imagery is in digital numbers — effectively sensor counts. To do anything scientific with it, you need to convert those numbers to top-of-atmosphere (TOA) reflectance, then run an atmospheric correction model to get surface reflectance. Surface reflectance is what makes imagery comparable across dates, sensors, and sun angles.

When you need it

Any time-series analysis. Any cross-sensor harmonisation. Any quantitative index where the absolute value matters (NDVI thresholds, biomass estimates, water quality). Without surface reflectance, your NDVI from January cannot meaningfully be compared to your NDVI from July — atmospheric water vapour and sun angle dominate the signal.

Custom corrections

Standard atmospheric correction models are tuned for typical land surfaces. Some workflows need custom corrections — aquatic remote sensing, for example, requires water-specific atmospheric correction because default models produce meaningless reflectance values over water. We run custom corrections on request, including lidar-aligned reflectance for carbon methodologies and aquatic-tuned corrections for water work.