Aerial Coverage of the Area of the Sanctuary of Zeus at Mt. Lykaion through ALS/LIDAR and High Resolution Imagery

The geometric documentation of a cultural heritage site is demanding task due to the complex morphology of the objects. The last years, more and more researchers have used new laser technologies and sophisticated computer vision techniques, mainly for terrestrial applications, with a complementary use of land surveying measurements. Although such technologies and processes provide efficiency, they are time-consuming with high cost for big covered areas with difficult accessibility. Aerial laser scanning (ALS/LIDAR) can contribute to the extraction of high-level information from huge cultural heritage sites for both structural and historical purposes.

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The wider area of the Sanctuary of Zeus at Mountain Lykaion is considered, among others, as one of the most important cultural heritage sites in Greece. This study aims to the aerial coverage of this area, that is, 117. 85 km2, through ALS/LIDAR and RGB high resolution imagery. At first step, the ALS/LIDAR point clouds and the RGB imagery were simultaneously acquired over the area of interest. The adjustment of neighboring ALS/LIDAR strips was firstly performed through strip alignment and then a georeference process using ground control points (GCPs) and check points (CPs) was carried out afterwards. The ALS/LIDAR point clouds were classified to extract bare-earth points. The bare-earth points were used to extract the corresponding Digital Terrain Model (DTM) of the area of interest. Also a fully automatic aerial triangulation of the aerial imagery was conducted using GPS/INS data. Finally, orthoimages were generated using the LIDAR/DTM. Also, the corresponding coloured ALS/LIDAR were created using the generated orthoimages. Point density varied considerably over the whole block depending on the ALS/LIDAR strip overlap. The ground sample distance () of the orthoimages was 10 cm.  The results demonstrate the utility and the functionality of ALS/LIDAR point clouds fused by high resolution aerial imagery for high-level 3D geometric documentation of huge cultural heritage sites.