Combining Multiband Imaging, Photogrammetric Techniques, and FOSS GIS for Affordable Degradation Mapping of Stone Monuments

Abstract

The detailed documentation of degradation constitutes a fundamental step for weathering diagnosis and, consequently, for successful planning and implementation of conservation measures for stone heritage. Mapping the surface patterns of stone is a non-destructive procedure critical for the qualitative and quantitative rating of the preservation state. Furthermore, mapping is employed for the annotation of weathering categories and the calculation of damage indexes. However, it is often a time-consuming task, which is conducted manually. Thus, practical methods need to be developed to automatize degradation mapping without significantly increasing the diagnostic process’s cost for conservation specialists. This work aims to develop and evaluate a methodology based on affordable close-range sensing techniques, image processing, and free and open source software for the spatial description, annotation, qualitative analysis, and rating of stone weathering-induced damage. Low-cost cameras were used to record images in the visible, near-infrared, and thermal-infrared spectra. The application of photogrammetric techniques allowed for the generation of the necessary background, that was elaborated to extract thematic information. Digital image processing of the spatially and radiometrically corrected images and image mosaics enabled the straightforward transition to a spatial information environment simplifying the development of degradation maps. The digital thematic maps facilitated the rating of stone damage and the extraction of useful statistical data.

From Qgis to Python: Comparison of Free and Open Tools for Statistical Analysis of Cultural Heritage and Data Representation

“…In summary, this paper stresses the importance of freely shared data and the power of geographic information tools in urban, architectural and heritage analyses. The free and open QGIS software has wide applicability on various scales in cultural heritage projects: from mapping materials to evaluating territories (Adamopoulos and Rinaudo, 2021). Citizens and experts can be involved in the decision-making processes of administrations, and public bodies can use open data provided by the local community (Roued-Cunliffe and Copeland, 2017).…”

Usage of a Conventional Device with LiDAR Implementation for Mesh Model Creation

“…Notably, Polycam was used for both LiDAR and photogrammetric processing. This resulted in four models: the Scaniverse model, 3D Scanner App Model, Polycam LiDAR model, and Polycam Photogrammetry model [45][46][47][48][49]. The scanning applications enabled us export the results of the scanning process in several spatial representations, including a mesh model, point cloud, and TIN model (Figure 5).…”

Close-Range Sensing and Data Fusion for Built Heritage Inspection and Monitoring—A Review

“…The reciprocity of visible-spectrum and infrared imaging is often considered essential for identifying damage on historic structures. Particularly, very near-infrared reflectance imaging is an effective tool for identifying biological colonization and the development of crusts on stone and concrete [167][168][169][170][171][172]. However, the cost and usability of hyperspectral/multispectral camera systems are often considered prohibitive factors for their implementation in the heritage sector, and thus the collection of multispectral data is performed via modified commercial cameras, and frequently with multi-sensor approaches.…”

“…Narrow or wideband external filters allow capturing reflectance data at the very near-infrared range, while the camera retains user-friendly features and interfaces to a wide variety of photographic accessories and software [173][174][175]. Adamopoulos and Rinaudo [167], Lerma et al [168], Meroño et al [169], and Sánchez and Quirós [176] have used this method to obtain visible and very near-infrared images aiming to identify weathering on historical stone buildings or masonry. Thermographic reflectance imaging can be performed with an additional sensor (Figure 6).…”