Use of robust methods to determine quadratic surfaces: application to heritage

3D surveys of archaeological elements and the construction of virtual models enable us to reconstruct historical sites. They provide useful data to select specific building processes.Photogrammetry and Terrestrial Laser Scanning (TLS) are the most common techniques to obtain synthetically heritage models. These techniques provide massive data which can only be managed by replacing them by primitive shapes, thereby obtaining more simple models and the explicit geometry of the element. Statistical and robust methods are used for this substitution, thereby avoiding the common errors due to measuring. Of these methods, the most widely used are the least-median-of-squares (LMedS) and the RANSAC method.Another computation method consists in recursive processes based on evolutive-type algorithms to adjust the model to the data captured.This paper describes two surface computation methodologies to determine the modelling of a column shaft located in temple G of the archaeological park of Selinunte (Sicily).     

Water, technology, and the courtroom: negotiating reclamation policy in territorial New Mexico

Historical investigation of arid landscapes and communities in the American West has long focused on the pivotal influence of federal reclamation policy, typically characterizing its implementation as the application of scientific and technological methods to a variety of water resource management issues. This paper departs from traditional views of reclamation by highlighting the highly variable and contingent ways in which new science-based forms of water management were proposed and negotiated in specific local places with particular cultural, legal, and historical geographies. Drawing theoretically from literature on the ‘geography of science,’ the paper probes the ways in which authority for a scientific approach to water management was created, negotiated, and expressed in local and regional contexts in the Territory of New Mexico, where authoritative systems of practical resource use and administration had been in long use before the U.S. government initiated its federal water reclamation program in 1902. Specifically, the paper examines two disputes entered and argued in front of northern New Mexico’s Rio Arriba District Dourt between 1903 and 1905. By departing from the geographical and scalar perspectives typically applied to environmental histories of the West and its reclamation landscapes, this ‘microgeographical’ approach promises a fresh perspective that emphasizes the highly contingent ways in which science-based water policy was implemented in multiple and complex environments.     

3D electrical prospection in the archaeological site of El Pahñú, Hidalgo State,Central Mexico

The implementation of a 3D Electrical Resistivity Tomography (ERT-3D) survey was carried out in El Pahñú archaeological site, Hidalgo State, Central Mexico. A combination of a new ERT arrays allowed studying the subsoil beneath the Main Pyramid built near the edge of a plateau, along with another important structure (the Tecpan), which was a smaller structure that lodged the governmental council in pre-Hispanic times. The recorded information was acquired through the combination of several electrodic designs: L-Corner (LC), Equatorial (Eq), and Minimum Coupling (MC). For the Main Pyramid, the electrodes were set up around the perimeter of the structure, since they were not permitted to be inserted over the edifice, thus preventing damages to the architectonic elements. The second structure allowed inserting electrodes on selected spots within the architectonic space. The combination of the different arrays made possible the acquisition of 1204 apparent resistivities beneath the Main Pyramid and 2460 resistivity data beneath the Tecpan. The apparent resistivity data were inverted to obtain a three dimensional display of the subsoil electrical resistivity beneath the archaeological structure. The interpreted resistivity model under the Main Pyramid displayed a highly resistive structure towards its northern face that could be associated with infill. Such material was employed by the ancient constructors to level the terrain close to the edge of the cliff. Another interesting anomaly was found towards the central portion of the structure that could be associated to a foundation offer. The interpretation of data beneath the Tecpan identified the structural foundations and other interesting anomalies related to the different occupational times. The investigation supported the archaeological investigation of the site, suggesting areas of potential geological risk and of archaeological interest. For example, the Main Pyramid presents serious stability problems, indicating that the infill has weakened, producing cracks threatening long-term pyramid integrity.