BRDF and its Impact on Aerial Archaeological Photography

Despite the arguments in favour of oblique photographs acquired during observer‐directed reconnaissance sorties, many aerial archaeologists have extracted much valuable information from verticals generated during total coverage mapping surveys. This paper looks at one of these arguments: the issue of anisotropic surface reflectance, which is responsible for the allegedly superior rendering of (mainly) vegetation and shadow marks when observed from certain oblique viewpoints. However, after a theoretical and practical assessment of the Bidirectional Reflectance Distribution Function (BRDF) of vegetation, it becomes clear that nadir views provide a more than satisfying alternative to the extremes of an oblique approach.