Balancing on the Borderline - a Low-cost Approach to Visualize the Red-edge Shift for the Benefit of Aerial Archaeology

Abstract

Scientists from different research disciplines have provided essential information that relates the biophysical characteristics of plants to their spectral reflectance. This fundamental understanding has facilitated the development of various non-destructive sensing methods for detecting vegetation stresses, monitoring plant growth and calculating crop yield. Aerial archaeologists flying in small aeroplanes have only partially exploited this knowledge. Instead of basing archaeological interpretation on only direct visual inspection of the conventionally acquired colour photographs, this contribution briefly reviews the reflectance properties of plants and uses them to present a new low-cost imaging technique beneficial for the detection of (faint) archaeologically induced vegetation marks. The new approach consists of three simultaneously operated digital still cameras, each of them capturing information in a different spectral waveband: the visible, near-infrared and red-edge spectral region. The latter two bands are used in the calculation of a R700/R800 vegetation index. Besides a theoretical underpinning, real-world examples will assess the potential of this new approach in detection of vegetation marks and prove that this low-cost, multispectral method might be beneficial in identifying and enhancing weak crop stresses that are lost when taking only the broad visible spectrum into account. In the final discussion, some thoughts on future archaeological aerial research are given.