A Comparison of Accuracy and Precision in Remote Sensing Stone-walled Structures with Google Earth, High Resolution Aerial Photography and LiDAR; a Case Study from the South African Iron Age

In the southern Gauteng Province of South Africa we have used Google Earth satellite imagery to survey some 8000 km(2) of landscape to record stone-walled structures. Around 7000 such structures have been located but we wonder how many, and which types of structures we have missed because of the relatively low resolution of Google Earth imagery, and how this might affect our interpretation of the archaeological sequence in the study area. Here we objectively compare three high resolution remote sensing views (low altitude aerial photography, LiDAR greyscale visualization and LiDAR hillshade visualization) of a 49 ha focus zone. We can confirm significant differences in the results from the different platforms, but each has its advantages. We then compare these results with our Google Earth survey within the same 49 ha focus area. Even though Google Earth imagery cannot match the high resolution views and fails to reveal significant detail which can negatively affect archaeological interpretations of the regional sequence of occupation, we conclude that for our large-scale regional remote sensing survey in the southern Gauteng it remains the only viable option for now. LiDAR and high resolution aerial photographs should be deployed on smaller areas of high interest to obtain maximum information, but they are impractical for regional coverage. Copyright (C) 2015 John Wiley & Sons, Ltd.