Optimized Planning of Terrestrial Laser-scanner Surveys in Complex Archaeological Environments

Abstract

The application of terrestrial laser scanning incomplex archaeologicalsites is an increasingly common fact in the last years. This equipment allows a quick and massive digitalization of the scanned surface, what reverts to achieve very detailed time series of the study area in a low-cost way. The main problem for this labour is to have the expertise to stablish the minimum number of scanning stations and their optimal location.If the archaeological site is really complex, the in situ decisions about the number and positions of scans can be very difficult only suitable for experts in laser scanning. Trying to provide a useful tool for archaeologists, this paper presents a methodology for planning and optimizing the scans locations taking advance of existing cartographic products. As a result, the archaeologist can plan the scanning surveying, improvingand optimizing the scan positions from the office. This approach was validated over the complex archaeological site of El Tolmo de Minateda located in Albacete (Spain). evaluate the quality of the results. In addition, an evaluation of the time savings provided by this methodology is performed, which is endorse by the efficiency of the fieldwork and the quality of the results. In particular, archaeologists do not have to spent time for the determination of the scans locations at the study area, and it is not necessary to perform the pre-processing of the point clouds at field for checking if the scanned areas present hidden areas and enough resolution. Based on authors' expertise in laser scanning works, we can establish a time saving of 33% in comparison with the classical laser scanning surveying.This is an important factor to take into account in public places with large number of daily visitors. Within this context, the paper has been organized as follows: After the introduction, materials section is described to carry out the proposed methodology; then the case study as well as the results obtained are outlined; and finally, the paper closes with the conclusions and future works section derived after the development of this research. Materials Three main geotechnologies were used in this complex archaeological settlement: (i) a paratrike, (ii) a digital camera and (iii) a terrestrial laser scanner. The paratrike employed was adapted to board several sensors in a stabilized gimbal. The stabilized gimbal maintains the camera orientation aiming to nadir during the flight. The digital camera used was a full frame reflex camera with a fixed focal length to achieve a ground sample distance (GSD) of 2 cm.