Fig. 6:

Simulated shadow effects of operator and instrument on the estimation of E_g from a level perfectly lambertian reflector. Differences in view geometry translate into different areas and fractions of the sky dome being shadowed. For the nadir view (θ_v = 0°), the blue line representing the Sun in the zenith is not shown, as shadowing of direct beam results in a ratio $E_{\text{g}}^{\text{est}.}/E_{\text{g}}^{\text{real}}$ < 0.2 in the visible range. Line colors represent the sky conditions from OC to clear skies with θ_s from 0° to 80°.