A Case Study of Measurement Uncertainty in Field Spectroscopy

In this article, a novel approach to measuring in situ field uncertainties in surface reflectance is presented. This work is an outcome of a national campaign by Geoscience Australia to validate our analysis-ready Landsat 8 and Sentinel 2 surface reflectance products. Various aspects of the field site methodology that were expected to contribute significantly to uncertainties were identified and tested. These aspects included the instrumental uncertainty, the use of a rest to stabilize the spectroradiometer fore-optic, the repositioning of the panel used for calibrating reflectance, and uncertainties introduced by the operator of the equipment, following a standard methodology. Results for two field sites are presented, which consistently show that approximately 95% of the overall uncertainty is a result of inherent variability in the ground surface reflectance. Typically, 5% of the uncertainty is introduced by a combination of the instrumentation and methodology.