Detection of buried archaeological remains with the combined use of satellite multispectral data and UAV data

Active and passive remote sensing sensors have been applied successfully in the detection of crop marks (vegetation with a different spectral reflectance compared to its surroundings) related with buried archaeological remains. However, the detection of such crop marks depends on the sensor used, the status of the cover and the algorithm applied on the data. Moreover, buried archaeological remains generally produce microrelief marks, which can be very difficult to detect. The purpose of this work is to demonstrate that the combined use of data from the multispectral orbital sensor WorldView-2 and RGB and near infrared cameras mounted on an Unmanned Aerial Vehicle (UAV) equipped with a Global Navigation Satellite System (GNSS) can be successfully applied to the detection of buried archaeological remains. Principal Component Analysis, the Normalized Difference Vegetation Index (NDVI) and a purposely proposed band combination were obtained from WorldView-2 data to detect crop marks. The cameras carried by the UAV provide a Real Color composite, the NDVI and a high precision Digital Surface Model. The methodology developed in this work consists of searching for locations that exhibit both crop and microrelief marks with a similar shape. The WorldView-2 NDVI and the normalized Digital Surface Model of the UAV are filtered. An Archaeological Binary Map is constructed, in which pixels with both NDVI and normalized elevation above corresponding threshold values are interpreted as susceptible of containing buried archaeological remains and are given the value of one, otherwise zero. One of the locations of the Archaeological Binary Map, with a very regular pattern, is subsequently surveyed with Ground Penetrating Radar to find a buried structure, the location and shape of which match perfectly those of the Archeological Binary Map.