University of Southampton OCS (beta), CAA 2012

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Combining Terrestrial Laser Scanning and techniques of digital image processing in “Archaeology of the Architecture” analysis, in the Walls of the Andalusian Site of Vascos (Navalmoralejo, Toledo-Spain)
María J. Iniesto-Alba, Miguel Bru, Estela Paradelo, Ricardo Izquierdo, Pablo Carballo Cruz

Last modified: 2012-03-26

Abstract


A challenge of archaeology is to analyze the history through chronotypology evolution of the material remains of cultural heritage. Firstly, this means that is necessary a 3D record, georeferenced, detailed and accuracy, and a three dimensional model that graphically represents both the geometry of the element under study and its current conservation state; secondly, after a detailed stratigraphic sequence, that allowing us to organize structural elements in time, we can propose the development of typologies linked to a specific chronology.This paper presents the work of 3D recording and geometric documentation of the walls of "Ciudad de Vascos" through specific methodologies of Archaeology of Architecture, such as the geometric definition and the measurement of its elements.The Archaeological Site of Vascos or City of Vascos is located at southwest of the province of Toledo (Spain), it´s one of the fortified enclosures of X-XI centuries most important of the Iberian Peninsula, which has fossilized the emirate-caliphate architecture of Al-Andalus, with little further transformation. In this way, the medina consists of two basic defensive elements, northwest of the city, the Kasbah, with several walled enclosures of different masonry, from mud to regular blocks. Closing the urban space, there is a vast wall of irregular shape, which well preserved in the most part. The wall presents different typologies with predominant of squared granite ashlars but there are also parts of little stones masonry fixed with mortar, which tell of different historical processes.Due to the large volume of data required to have a metric knowledge to determine typologies, and in order to facilitate and automate the process of obtaining measurements, we have implemented a technique that aims to combine the high-resolution of terrestrial laser scanner, with digital images processing, to obtain the largest number of metric data that distinguish each typology.We carried out a survey of the wall with a SLT (Leyca ScanStation C10), for the geometric and volumetric reconstruction; in addition we used a GPS to give absolute coordinates to the work. After data capture, it is necessary a process of depuration of the point clouds and a mesh was created with a resolution of centimeters to obtain the 3D textured model and a serie of plan or sections, like first results of the project, as well as a series of orthoimages that will support archaeological stratigraphy units.With these orthoimages be held the draw and measurement of ashlars, masonry blocks and areas of interest, using techniques of digital image processing, mainly, image enhancement, edge detection and filters in order to automate the process of defining structural elements. Them, we will proceed to the automatic extraction of numerical data of the elements of the wall, that is, the dimensions, as a contribution to the technique mensiochronology. Finally, verification of results ensures that the proposed methodology allows obtaining precise and quality data.

Keywords


Terrestrial Laser Scanning (LTS); digital image processing; Archaeology of the Architecture; Andalusian Site of Vascos