Virtual Modelling of Prehistoric Sites and Artefacts by Automatic Point-Cloud Surveys

Virtual Modelling of Prehistoric Sites and Artefacts by Automatic Point-Cloud Surveys

Mercedes Farjas (Universidad Politécnica de Madrid, Spain), Francisco J. García-Lázaro (Universidad Politécnica de Madrid, Spain), Julio Zancajo (Universidad de Salamanca, Spain), Teresa Mostaza (Universidad de Salamanca, Spain) and Nieves Quesada (Universidad Politécnica de Valencia, Spain)
DOI: 10.4018/978-1-61520-631-5.ch012

Abstract

This chapter presents laser scanner systems as a new method of automatic data acquisition for use in archaeological research. The operation of the equipment is briefly described and results are presented from its application in two Spanish archaelogical sites: Abrigo de Buendía (Cuenca), Atapuerca (Burgos). Together with these systems, point cloud measuring photogrammetric methods are revised. Photogrammetry has been widely used in heritage documentation and in no way is to be relegated by the new scanning techniques. Instead, Photogrammetry upgrades its methods by applying digital approaches so that it becomes competitive in both, operational costs and results. Nevertheless, Photogrammetry and laser scanner systems should be regarded as complementary rather than competing techniques. To illustrate photogrammetric methods their application to generate the Digital Surface Model of an epigraph is described. The authors’ research group endeavours to combine teaching and research in its different fields of activity. Initial data are acquired in project-based teaching situations and international seminars or other activities. Students thus have the opportunity to become familiar with new methodologies while collecting material for analytical studies.
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Introduction To Laser Scanners

A 3D scanner is a data acquisition system which analyses an object or surface to acquire information on its shape, measurements and colour. This information can subsequently be used to construct three-dimensional models and extrapolate the shape of the object under study.

3D scanners operate in a way very similar to cameras. Like cameras, they have a conical field of vision and can acquire information from lighted surfaces. While a camera acquires colour information on the surfaces within its field of vision, 3D scanners capture other surface data, so that by combining geometrical features with photographs the optimum representation of the object is achieved.

An introductory text on the subject in Spanish can be found in Farjas and García-Lázaro (2008).

The type of 3D scanner normally used in three-dimensional modelling is an active non-contact scanner, which is placed at a certain distance from the object and projects a beam onto the object or its surroundings from short or long range. The type of beam used may be light, ultrasound or x-rays. Long range systems work at distances of from 3 to 300 metres and provide measurements correct to within one centimetre. Short range systems are placed at less than 3 metres and are correct to less than a millimetre. There may also be differences in the type of measuring system and the type of sweep. The different systems include the following:

Different types of measuring system:

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