Gabriella Caroti

Frescoed Vaults: Accuracy Controlled Simplified Methodology for Planar Development of Three-Dimensional Textured Models

In the field of documentation and preservation of cultural heritage, there is keen interest in 3D metric viewing and rendering of architecture for both formal appearance and color. On the other hand, operative steps of restoration interventions still require full-scale, 2D metric surface representations. The transition from 3D to 2D representation, with the related geometric transformations, has not yet been fully formalized for planar development of frescoed vaults. Methodologies proposed so far on this subject provide transitioning from point cloud models to ideal mathematical surfaces and projecting textures using software tools. The methodology used for geometry and texture development in the present work does not require any dedicated software. The different processing steps can be individually checked for any error introduced, which can be then quantified. A direct accuracy check of the planar development of the frescoed surface has been carried out by qualified restorers, yielding a result of 3 mm. The proposed methodology, although requiring further studies to improve automation of the different processing steps, allowed extracting 2D drafts fully usable by operators restoring the vault frescoes.

Structure from motion (SfM) processing of UAV images and combination with terrestrial laser scanning, applied for a 3D-documentation in a hazardous situation

ABSTRACT The integration of Terrestrial Laser Scanning (TLS) and Structure from Motion and MultiView Stereo techniques allows to obtain comprehensive models of complex objects by using each technique in contexts presenting the optimal operating conditions, as widely reported in bibliographic references. A different situation occurs for emergency surveys. In this case, time and security act as constraining factors, requiring the use of these techniques also in the most unfavourable conditions. In the case of photogrammetry, these include areas where the object surfaces are not perpendicular to the camera axis, and in the case of TLS, they include areas where laser beams are almost tangent to the surveyed object surfaces. These situations are anyway necessary for safely carrying out these surveys in the minimum possible time and cost. Although this kind of survey results locally in lower precision levels than those obtainable by these techniques in ideal conditions, it entails the possibility of obtaining complete models, e.g. including vertical external walls in inaccessible buildings, with controlled precision.

Kinematic Positioning: From Mobile Mapping Systems to Unmanned Aerial Vehicles at Pisa University

Since the 1990s, with the availability of satellite positioning techniques, enabling to determine three-dimensional point coordinates in a global reference system with topographic accuracy, several applications dedicated to mapping of the territory by means of mobile geo-referenced sensors have steadily been developed. This paper discusses the experiences gained in this field at the University of Pisa—Laboratory of Topography over more than twenty years of experimental work. These activities, often conducted in cooperation with the University of Trieste and in particular with Professor Giorgio Manzoni, have always featured a multidisciplinary approach. Different types of sensors have been installed, at first in land-based vehicles and currently on unmanned aerial systems: GPSs, GNSSs and INSs, carbon monoxide and particulate matter measuring systems, single- and multiple-axis laser scanners, industrial and photography cameras. Use of these sensors, besides drafting and testing maps of the territory in several areas (cartography, road cadastre, pollution monitoring, city modelling …), allowed to keep track of the development of instrumentation and methods of kinematic positioning.

UAV-Borne Photogrammetric Survey as USAR Firefighter Teams Support

Fire Departments feature specialized teams for Urban Search And Rescue (USAR) activities, operating in case of disasters and in collapse contexts, where the actual situation no longer coincides with any previous survey. In this context, current UAV-borne photogrammetry may offer very effective methods, enabling achievement of to-date knowledge of the status quo. Their effectiveness in these contexts is due to the ability of drones to operate in triple-D areas (Dull, Dusty, Dangerous) and to the remote sensing features inherent in photogrammetry.

Low-Altitude UAV-Borne Remote Sensing in Dunes Environment: Shoreline Monitoring and Coastal Resilience

UAV systems, fitted with either active or passive surveying sensors, can provide land-related measures and quantitative information with low costs and high resolution in both space and time. Such surveying systems can be quite valuable in defining geometrical and descriptive parameters in coastal systems, especially dune ecosystems. The present work is based on a survey of the dune system at the mouth of the Fiume Morto Nuovo in the San Rossore Estate (Pisa) and focuses on comparing LiDAR with UAV- and airplane-borne photogrammetry, as well as the respective 2D and 3D cartographic output, in order to assess topography changes along a stretch of coastline and to check their possible use in defining some ecological resilience features on coastal dune systems. Processing of survey data generates a Digital Surface Model (DSM) or Digital Terrain Model (DTM) and an orthophotograph, checked for accuracy and image resolution. Comparison of these products against those available in public access cartographical databases highlights differences and respective strengths.

A Methodology for Planar Representation of Frescoed Oval Domes: Formulation and Testing on Pisa Cathedral

This paper presents an original methodology for planar development of a frescoed dome with an oval plan. Input data include a rigorous geometric survey, performed with a laser scanner, and a photogrammetry campaign, which associates a high-quality photographic texture to the 3D model. Therefore, the main topics include the development of geometry and, contextually, of the associated textures. In order to overcome the inability to directly develop the surface, an orthographic azimuthal projection is used. Starting from a prerequisite study of building methodology, the dome is divided into sectors and bands, each linked with the maximum acceptable deformations and the actual geometric discontinuities detectable by the analysis of Gaussian curvature. Upon definition of the development model, a custom automation script has been devised for geometry projection. This effectively generates a (u,v) map, associated to the model, which is used for model texturing and provides the planar development of the fresco.

Digital Technology and Mechatronic Systems for the Architectural 3D Metric Survey

Over the last decade, we have seen the widespread use of digital survey technologies that have made the three-dimensional (3D) metric survey within reach of all. In the past, lengthy training was needed to use total stations and classical photogrammetry. Today, laser scanning and “new photogrammetry” allow operators with little training to produce 3D models with high spatial density in real time. These systems have therefore made 3D metric survey available to a wide audience of professionals, and have also allowed surveys to be performed with little economic investment in instrumentation. Although this evolution in survey methodologies has certainly brought great benefits, the use of these methods by operators with limited training poses some risk. The proliferation of imprecise processed 3D data, however, constitutes a digital archive of documentation which, by its nature, should be semi-automatically integrated. Issues related to reference systems, scale of representation, accuracy, and related metadata therefore become highly relevant. This paper aims to describe, by means of several case studies, the laser scanner and “new photogrammetry” survey methodologies in light of the aforementioned issues. In addition, the use of “new photogrammetry” in combination with UAV systems will be presented. The integration and miniaturization of positioning systems, attitude measuring systems, and survey instruments (cameras, laser scanners, thermal and multispectral cameras, etc.) allow, by drone flight, the creation of 3D surveys, something that was impossible several years ago without a substantial budget for the use of conventional aircraft.