Comparison of DSMs generated from mini UAV imagery and terrestrial laser scanner in a cultural heritage application

In this paper we present two different methods, which were applied for the DSM generation of the cultural heritage site Pinchango Alto. The area of interest is a LIP (Late Intermediate Period; 1400 AD) settlement, situated 400 km in the south of the capital of Peru (Lima) close by the famous Geoglyphs of Nasca. The site was recorded using a terrestrial laser scanner (Riegl LMS-Z420i) and a mini UAV-system (Unmanned Aerial Vehicle) under the framework of a research program called NTG (“New methods and technologies in the humanities”). During the field work, using both methods, the complete settlement was documented in a short time. The post-processing of the data was done by use of in-house developed software packages. The image data (UAV) were oriented and a DSM (10 cm resolution) was generated automatically using a multi-image matching approach. For the registration of the single laser scans a surface matcher rather than the special targets was used. As a product of the laser data a regular raster grid with point spacing of 5 cm was generated. The 3D comparison of both elevation models shows a mean value less than 1 cm with a standard deviation of 6 cm. The main discrepancy between the data sets results mostly from occlusion, caused on the restricted viewing directions of the acquisition stand points. The presented data acquisition and processing methods showed their high usability for the documentation of archaeological sites.