The effect of cloud and solar zenith angle on spectral reflectance data collected in the field

Remote sensing studies of vegetation are frequently supported by in situ spectral reflectance measurements. However, collecting these measurements in the field is frequently expensive, both in terms of time and financial commitments. While it is generally recommended that spectral reflectance measurements are acquired on clear, windless days within 2 hours of solar noon, such ideal weather conditions are often illusive, forcing the researcher into a decision whether to abandon their fieldwork or to try and extend their collection activities into less-than-ideal conditions. In this paper we measured the effects of variable atmospheric opacity (i.e. cloud cover) and solar zenith angles on in situ spectral reflectance measurements and found that, with frequent instrument calibration, it is possible to collect useable spectra.