Laser Scanning for the Evaluation of Historic Structures

Introduction

In this section a general perspective of laser scanning technology is presented. During the last decade this technology has experienced an important evolution, and nowadays it is more and more in demand in order to perform detailed and accurate geometric characterizations of finished constructions. This surveying method was also successfully applied to other different fields, such as archaeological and architectural documentation (Pesci et al., 2012; González-Aguilera et al., 2008), civil engineering (Lovas & Berényi, 2009; González-Jorge et al., 2012), or the as-built modelling of industrial plants (Rabbani et al., 2007), among others. Particular applications to historic structures can be seen in Riveiro et al. (2011a), who developed a methodology that allowed the converting point clouds acquired by terrestrial laser scanning into metric images that were subsequently used for stability analyses of masonry arches; Armesto et al. (2010a) used a dense set of points combined with statistical methods to perform accurate an geometric diagnosis of masonry arches in the Roman Bridge; McInerney et al. (2012) and Milani et al. (2013) used the technique to automatically create geometric block models of masonry walls; Armesto et al. (2010b) used a combination of geometry and intensity data for detecting and quantifying the presence of superficial pathologies in masonry buildings; Solla et al. (2014) developed integrated approaches using laser scanning and ground penetrating radar (GPR) to create synthetic models of masonry arch bridges to assist the interpretation of the GPR data.

These experiences and many others have validated the potential of laser scanning in the field of structural engineering, particularly when tackling the evaluation of historic structures where detailed design plans are not usually available. Also, the actual geometry of the structure plays a crucial role in an objective and accurate assessment of their structural behaviour. Laser scanning has gained popularity because it fulfils the requirements mentioned above, but also because it is a remote, non-destructive method that ensures the safe survey of historic structures. Nowadays, the advances in automatic data processing are allowing the implementation of laser scanning to more particular applications, also by enabling access to the technology by non-experts in geomatics.

This chapter is organized in order to demonstrate the state-of-the-art of laser scanning technology; additionally, an overview of the principles of the operation of laser scanners is presented in the background section. Two main typologies of land platforms are described: static scanners, also known as Terrestrial Laser Scanners (TLS) and Mobile Laser Scanners (MLS). Later, the advantages and disadvantages of each typology will be discussed.