Diego González-Aguilera

An Automatic Approach for Radial Lens Distortion Correction From a Single Image

Radial lens distortion correction is a fundamental task in photogrammetry and computer vision disciplines, mainly when metric and quality results are required. Radial lens distortion estimation plays an essential role in several photogrammetric tasks such as: registration of sensors, 3-D reconstruction, and mapping of textures. This paper presents an iterative numerical approach for the automatic estimation and correction of radial lens distortion using only a single image. To this end, several geometric constraints (rectilinear elements and vanishing points) are considered. The reported experimental tests indicate that within certain limits, results from a single image can stand the comparison with those from multiple image bundle adjustment.

Trimble GX200 and Riegl LMS-Z390i sensor self-calibration

This paper aims to establish and develop a calibration model for two time-of-flight terrestrial laser scanners (TLS): Trimble GX200 and Riegl LMS-Z390i. In particular, the study focuses on measurement errors and systematic instrumental errors to compile an error model for TLS. An iterative and robust least squares procedure is developed to compute internal calibration parameters together with a TLS data set geo-reference in an external reference system. To this end, a calibration field is designed that performs as an experimental platform that tests the different laser scanner methods. The experimental results show the usefulness and potential of this approach, especially when high-precision measurements are requires.

Metrological comparison of terrestrial laser scanning systems Riegl LMS Z390i and Trimble GX

A low cost physical artifact with traceability to the national standard - meter is used for the metrological comparison of two terrestrial laser scanning systems: Riegl LMS Z390i and Trimble GX. The artifact is based on five spheres equidistantly situated and seven cubes of different dimensions. Accuracy and repeatability are evaluated using least squares fitting (LSF) and random sample consensus algorithms, for the study case of the spheres, and plane LSF and statistical analysis for the cubes. The horizontal resolution is evaluated using a modulated transfer function approach and the vertical one with the accuracy and repeatability data along Z axis. The Trimble system shows better results for all parameters, artifact parts, and algorithms under study.

Application of Non-Destructive Techniques to the Recording and Modelling of Palaeolithic Rock Art

1.1 Motivation According to Spanish legislation and international organisations such as UNESCO, the Council of Europe and the European Union, historical and artistic heritages should be preserved and placed in the service of society for either cultural, scientific or educational purposes. Thus, it is necessary to document and invest in their preservation, restoration, rehabilitation and/or archival for subsequent scientific studies (Elwazani, 2003), in addition to documenting their dissemination and social value. Archaeological remains are part of peoples’ historical artistic heritage and represent a testimony of their past. The attitude and sensibility towards this cultural inheritance say much about our future as a society. The documentation of general heritage and particularly archaeological heritage properties is indispensable before performing any type of measure or intervention. Such documentation implies recording, storing, cataloguing and measuring the elements that compose the heritage property. With regards to archaeological heritage, these tasks are developed both with elements that comprise movable heritage (for example, bone and lithic industries) and with elements that comprise non-movable heritage (for example, buildings, fields and caves). The geometric component of archaeological documentation begins with measurement and has the objective of a graphical representation, using multiple strategies and support. The act of measuring implies a quantification of the spatial characteristics of an object, especially its shape, dimensions, orientation and location, both in its immediate environment and in relation to the global geographic context. In the geographic documentation of heritage, the measurement and graphical representation are indivisible tasks. Particularly, the traditional procedures of documentation and graphical representation are based on employing equipment that has a low cost and is easy to use. Despite the effectiveness of these procedures, they exhibit a series of inconveniences, such as the large amount of time required to acquire data, the limit of work within a twodimensional scope, the loss of information during data transfer and the need to physically

From the point cloud to virtual and augmented reality: digital accessibility for disabled people in San Martin's Church (Segovia) and its surroundings

This article explains the working methodology followed to carry out a project in which the 3D laser scanner survey of San Martins Church (placed in Plaza Juan Bravo, in the historic city centre of Segovia Spain), has been undertaken. There is also a virtual tour through the nearby streets, which lead us to the Jewry Museum, going through the Paseo del Salon. The final aim is to obtain derivative CAD products such as technical plans, solid models and different videos, as well as a simplified 3D model. This project has been funded by the MICINN (Ministerio de Ciencia e Innovacion [Department of Science and Innovation]), within the project ADISPA, BIA2009-14254-C02-01, and will constitute a mathematical base of a scenario of augmented reality which will make accessibility for disabled people possible. This will be framed within the PATRAC project (PATRIMONIO ACCESIBLE: I+D+I para una cultura sin barreras [ACCESSIBLE HERITAGE: R+D+I for a culture without barriers]).

Architectural orthophoto plan for pathological characterization of the Medieval Wall of Avila

This article presents the development of a specific architectural orthophoto plan applied to the Medieval Wall of Avila, with the aim of obtaining a high quality cartographic product which allow us to undertake actions for pathological and structural characterization. This product must provide support for decision making concerning the pathology and structural characterization of the wall. To this end, a combined use of geomatics non-destructive techniques, specifically laser scanning and close-range photogrammetry will be applied. As a result of this integration, orthophotos with a pixel size of 4mm (GSD) will be obtained, constituting a tool with great potential for the different actors involved in the management of the conservation and restoration of this valuable monument.

Integration of TLS, close range photogrammetry and spatial information systems

This paper describes a methodology based on combining TLS and close range photogrammetry aimed at generating the geometry of 3-D surfaces as well as 3D real textured models and map products for further study. Also, a spatial information system based on spherical photograph is presented that allows performing virtual tours as well as geo-referencing graphical or numerical data derived from the TLS or photogrammetric survey. The methodology is applied to the survey of the Llonín Cave, Asturias, in the Northwest of Spain.