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.

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