Ground reflectance measurement techniques: a comparison.
The relative accuracies of reflectance factor measurement methods involving the simultaneous, as compared to the sequential, measurement of irradiance on and radiance reflected from the target are discussed. Data are presented to support a statistical demonstration that the simultaneous measurement technique is the more accurate.
On the variability of the reflected radiation field due to differing distributions of the irradiation
Abstract The directional reflected radiation of natural surfaces may change even if nothing save the distribution of the irradiation over the hemisphere varies. This is due to the angular anisotropy of the reflection properties of natural surfaces. The quantitative determination of this effect for four different vegetated surfaces is the aim of this investigation. In this paper, results for the first of the four surfaces, a savannah, are shown. The directional reflected radiation may change by ± 1% per degree change of the solar zenith angle and by ± 1 per 6% change of the spectral atmospheric turbidity factor at 0.52 μm.
The qualitative research interview
Background  Interviews are among the most familiar strategies for collecting qualitative data. The different qualitative interviewing strategies in common use emerged from diverse disciplinary perspectives resulting in a wide variation among interviewing approaches. Unlike the highly structured survey interviews and questionnaires used in epidemiology and most health services research, we examine less structured interview strategies in which the person interviewed is more a participant in meaning making than a conduit from which information is retrieved.