Geomatic Techniques Research Articles

Reconstructing archaeological palaeolandscapes using geophysical and geomatic survey techniques: An example from Red Lily Lagoon, Arnhem Land, Australia.

Arnhem Land is a key region for understanding the Pleistocene colonisation of Australia, due to the presence of the oldest sites in the continent. Despite this, conventional archaeological survey has not been effective at locating additional pre-Holocene sites in the region due to a complex distribution of geomorphic units caused by sea level rise and coastal aggradation. This research uses geophysical and geomatic techniques to map the subsurface distribution of the geomorphic units in the Red Lily Lagoon region in eastern Arnhem Land. This reveals a complex Pleistocene landscape, which offers the potential to locate additional archaeological sites and so reveal more about the lifeways of the earliest Australians.

Integration, harmonization, and processing of geomatic data for bridge health assessment: the Lastra a Signa case study

A visual inspection, which entails field surveying, such as photodocumentation and footage, is the first step of a multi-level approach to bridge health assessment. Furthermore, the use of surface models, CAD drawings, and orthophotos, guarantees complete and accurate documentation, thus allowing for a better understanding of the environment, the anthropic structures, and their relationships. All the georeferenced surveys’ outputs are especially advisable within a prespective of periodical monitoring, as forseen by national legislation. The work is aimed to study two adjacent bridges over the Arno River in Lastra a Signa, Italy. One of the bridges, Ponte nuovo sull’Arno, is an overpass for motor vehicles. The other one, which is called Passarella sull’Arno, is a pedestrian viaduct. A topographic reference network has been settled using the GNSS survey technique. 3D point clouds of the bridges have been acquired by performing a Laser Scanning survey. A bathymetric survey has been carried out to acquire a 3D point cloud of submerged bridges’ parts and the riverbed. Through a Photogrammetric survey from RPAS, an orthophoto of the area has been built. Finally, evidence of historical submerged bridge structures has been identified thanks to the multi beam survey. The work’s objective is to integrate surveying geomatics techniques to create a reliable survey of the bridges, the surrounding area, and the riverbed, as support to the most common structural health assessment methods.

New Methodology for Shoreline Extraction Using Optical and Radar (SAR) Satellite Imagery

Coastal environments are dynamic ecosystems, constantly subject to erosion/accretion processes. Erosional trends have unfortunately been intensifying for decades due to anthropic factors and an accelerated sea level rise might exacerbate the problem. It is crucial to preserve these areas for safeguarding not only coastal ecosystems and cultural heritage, but also the population living there. In this context, monitoring coastal areas is essential and geomatics techniques, especially satellite remote sensing imagery, might prove very advantageous. In this paper, a semi-automatic methodology to extract shorelines from SAR (Synthetic Aperture Radar) Sentinel-1 and optical Sentinel-2 satellite images was developed. An experimental algorithm, called J-Net Dynamic, was tested in two pilot sites. The semi-automatic methodology was validated with GNSS (Global Navigation Satellite System) reference shorelines and demonstrated to be a powerful tool for a robust extraction of the shoreline both from optical and SAR images. The experimental algorithm was able to extract the shoreline closer to the reference with SAR images on the natural beach of Castelldefels and it was demonstrated to be less sensitive to speckle effects than the commonly used Canny Edge Detector. Using the SAR images of the urban beach of Somorrostro, the Canny detector was not able to extract the shoreline, while the new algorithm could do it but with low accuracy because of the noise induced by man-made structures. For further investigation, the Sentinel-2-extracted shorelines were also compared to the ones extracted by a state-of-the-art tool, CoastSat, in the two beaches using both automatic and manual thresholds. The mean errors obtained with J-Net Dynamic were generally higher than the ones from CoastSat using the manual threshold but lower if using the automatic one. The proposed methodology including the J-Net Dynamic algorithm proves to extract the shorelines closer to the reference in most of the cases and offers the great advantage of being able to work with both optical and SAR images. This feature could allow to reduce the time lag between satellite derived shorelines paving the way to an enhanced monitoring and management of coastal areas.

Reliability-based structural assessment of historical masonry arch bridges: The case study of Cernadela bridge

Nowadays, several historical masonry arch bridges present a deficient state of conservation due to degradation processes induced by natural or human actions. Usually, these constructions have significant economic, cultural, and heritage value. Therefore, they shall be thoroughly assessed to verify their structural integrity and safety condition. For this purpose, reliability-based structural assessments are typically performed. However, the associated outcomes (i.e., reliability index and probability of failure) highly rely on the accuracy of the structural parameters uncertainty quantification. This work presents a study regarding the influence of the scattering of the arches' thickness dimensions in the load-carrying capacity assessment of the Cernadela Bridge, a historical stone bridge located in Galicia, Spain. The study first involved a comprehensive experimental campaign to characterize the outer and inner bridge geometry through geomatic techniques, i.e., terrestrial laser scanning and ground penetrating radar. Subsequently, a limit analysis model was developed, considering only the arches' outer (visible) data. From this initial structural assessment, a reliability index of 2.38 was obtained. The influence of the uncertain structural parameters, both geometric features and material properties, in the collapse load was investigated through a global variance-based sensitivity analysis (i.e., Sobol' indices) complemented by a surrogate modeling strategy based on the Kriging approach. Finally, the measured inner geometry of the arches was introduced in the computational model through Bayesian inference procedures. Thus, two new structural assessments were performed: first, by considering the updated distributions of all arches thicknesses, and second, by considering only the updated distributions of the non-influential ones. Reliability indexes of 1.51 and 2.33 were derived, thus highlighting the importance of a proper uncertainty quantification process and the relevance of the sensitivity analysis outcomes to identify the critical parameters on the bridge mechanical response.

Multitemporal and Multiscale Applications of Geomatic Techniques to Medium-Sized Archaeological Sites—Case Study of Marroquíes Bajos (Jaén, Spain)

This study describes a methodology for obtaining a geometric documentation of a medium-sized archaeological area by applying various geomatic techniques. The procedure considers the obtainment of products at several scales, from the entire site to small artifacts, and at several dates, in order to model the evolution of the archaeological work. The methodology includes both LiDAR and photogrammetry, using the LiDAR point clouds to support the geometry obtained using photogrammetry and adding texture from this source. The technique used was adapted to the circumstances of the scene by considering the scale level (resolution and accuracy), complexity, and other requirements of the project. In the case of LiDAR, terrestrial laser scanning and structured-light scanning were used, and the aerial photogrammetry used two types of RPAS (medium and low flight height), close range photogrammetry with a conventional camera, and very close-range photogrammetry with a conventional camera mounted with a macro lens. The methodology demonstrated its feasibility for performing these types of studies, providing products adapted to the required scale level. All results were integrated into a website, including a map that allows user interaction and displays products at a selected zoom level, according to their scale level. The website also displays 3D models of the scenes and objects studied.

Expeditious Low-Cost SfM Photogrammetry and a TLS Survey for the Structural Analysis of Illasi Castle (Italy)

The structural analysis of degraded historical buildings requires an adequate 3D model of the object. Structure from motion (SfM) photogrammetry and laser scanning geomatics techniques can satisfy this request by providing geometrically affordable data. The accuracy and resolution depend on the instruments and procedures used to extract the 3D models. This work focused on a 3D survey of Illasi Castle, a strongly degraded historical building located in northern Italy, aimed at structural analysis in the prevision of a static recovery. A low-cost drone, a single-lens reflex (SLR) camera, and a smartphone were used in the survey. From each acquired dataset, using the integration between the images acquired by the drone and the SLR camera, a 3D model of the building was extracted by means of the SfM technique. The data were compared with high-precision and high-resolution terrestrial laser scanning (TLS) acquisitions to evaluate the accuracy and performance of the fast and low-cost SfM approach. The results showed a standard deviation value for the point cloud comparisons in the order of 2–3 cm for the best solution (integrating drone and SLR images) and 4–7 cm using smartphone images. Finally, the integration of the best SfM model of the external walls and the TLS model of the internal portion of the building was used in finite element (FE) analysis to provide a safety assessment of the structure.

Applying Geomatics Techniques for Documenting Heritage Buildings in Aswan Region, Egypt: A Case Study of the Temple of Abu Simbel

It has recently become more popular to involve 3-D modeling and digital documentation in the conservation and restoration of heritage sites. The main objective of the current study is to develop a digital documentation process using laser scanning for Abu Simbel Temple, which is one of the most famous archaeological sites in Egypt. We focus on these techniques to replace traditional methods of building heritage documentation. To create the 3-D model with geographic coordinates and measure the rate of deformation, a precise geodetic network of five points was established around the temple. Then, 52 scans of the temple facade and its interior parts were taken using a Trimble TX6 laser scanner. This led to the creation of a 3-D digital model of the temple that includes geometric, structural, architectural, historical data, and non-engineering information (such as appearance, inscriptions, and material details). The 3-D point cloud model outputs exhibit a 6 mm spacing between the points with an error of 4 mm and a standard deviation of 5 mm. In addition, the temple’s virtual tour included 61 panoramic images. This virtual tour can help to increase heritage awareness, promote tourism, and aid in the future restoration of any parts vulnerable to damage.

Exploiting 2D/3D Geomatics Data for the Management, Promotion, and Valorization of Underground Built Heritage

The scarce knowledge and documentation of Underground Built Heritage (UBH) assets frequently limit their full exploitation and valorization. The aim of this work is to reflect on the techniques, functions, and technical features of a specific case study in a very broad context that can, however, be a building block for the understanding, preservation, and reuse of architectural and engineering values that represent a fundamental trace of the history of a society. Therefore, to fill these knowledge gaps, it was constructed a 3D GIS model, multi-scale, and interoperable database, capable of management, promotion, and valorization of UBH. The case study focuses on the old water supply system of the city of Lisbon, as UBH site, with galleries and cisterns that are points of connection with the urban environment above. For the creation of 3D models of the structure under investigation, it was decided to carry out a survey with Mobile Mapping System as a first step, which allowed the construction of a dense point cloud useful to build 3D models of individual objects. Finally, the 3D models were imported into the 3D GIS environment and multi-information could be linked for each previously identified element for greater knowledge sharing. This research has demonstrated how geomatic techniques can be effectively used in conjunction with the information management systems of GIS to explore this “hidden” heritage and has highlighted the limitations and problems of 3D digitization of the UBH. The results obtained offer the possibility of extending and adapting the methodology to different application contexts and the possibility of customizing the data representation.

Building 3D Object Model for Tourism in Monas using CityEngine

A prominent monument in DKI Jakarta is the Monument Nasional (abbreviated as Monas). This moniker serves as both a symbol for the city of Jakarta and a representation of the people of Jakarta and Indonesia. Apart from being a monument, Monas also has a history of the Indonesian nation. In this study, 3D models are designed to display visualizations of Monas and surroundings in 3D form with the aim of helping tourists who want to visit Monas in preparing and increasing their understanding of the tourism in Monas. This study was conducted with the help of CityEngine software that created the 3D models of Monas implemented and displayed on a website with a web scene format. Using image-based 3D modelling, the main geomatics techniques is photogrammetry, it allows for new methods to create virtual 3D. To do this, various components including route visualizations must collaborate. To do this work we have a framework that leverages the technology and data sources already available to reduce the time and work required for prospective 3D applications. With the existence of a Monas 3D visualization that can be accessed through web browser, it expected that it will make tourists not complicated to obtain various tourism information and increase the tourism in Jakarta.

Application of Geomatic Techniques for the Assessment of Anthropogenic Changes in the Urban Beaches of “La Magdalena” (Santander, Spain)

Since the 1970s, dredging sands have been poured onto the embayed beaches of La Magdalena in the western mouth of the estuarine Bay of Santander (N Spain) in order to increase beach width. Up until the year 2000, the sands were systematically fed by a trailing suction dredge, which was later replaced by truck sand transfers from the surplus sands of the western beach to the eastern ones and by mechanical redistribution to create artificial berms. A recent project aimed to solve sand losses after each storm by building two perpendicular breakwaters about 620 m apart. The eastern breakwater was built in the early summer of 2018, and wave storms in November 2018, February 2019, October 2020 and the last days of 2021 progressively dismantled the reconstructed upper beach areas and eroded other segments. The western breakwater, however, designed to retain the E–W sandy beach drift, was never built. Four photogrammetric restitutions from 2005, 2010, 2014 and 2017 and an aerial LiDAR in 2012 were obtained to better understand the previous topographic distribution of the back and foreshore. Numerous field observations were made, and six field surveys have been performed since 2018 using laser TLS and GNSS, which occurred in November 2018, March 2019, October 2019, March 2020, October 2020 and April 2021. The definitive results of the evolution of the sand loss are presented, a hypothesis is proposed to explain the dynamo-sedimentary trend, in which longitudinal transport dominates promoting the formation in the progress of a new sand beach, and some sustainable solutions are proposed. The results show that the constructive solution has failed to stabilize the beach and that the predictive models that justified it have not coincided with the real dynamic and sedimentary evolution.

3D Modelling Building of District Johar Baru Using ArcGIS Pro and CityEngine

Various image-based approaches are currently available for 3 Dimensional (3D) modelling. Among them, two main geomatics techniques are photogrammetry and laser scanning. Owing to the limited availability of photographs to the general populace, the employment of satellite and aerial photogrammetry is rather intricate. In light of Jakarta's absence of a comprehensive three-dimensional portrayal, there is an impetus to generate accurate, precise, and detailed tri-dimensional visualizations of a particular sector within Jakarta, specifically Johar Baru. This endeavor shall be undertaken through a technique termed LoD, with ArcGIS and CityEngine serving as the fundamental instruments for this initiative. To do this, we provided a framework that leverages existing technologies and data sources to reduce the time and work needed for prospective 3D indoor routing applications. Our indoor and building 3D models were created using the CityEngine procedural modelling approach from CAD files and building footprints. This work does not address data delivery or administration; it primarily focuses on 3D visualization. Cadastral, visualization, and non-functional requirements are the three main areas of 3D visualization requirements against which CityEngine was assessed. A case study corresponding to a real issue that has already been recognized in Portugal is used to evaluate the problem. The results are encouraging. The CityEngine won't be the best choice for all users because of the steep learning curve. Using CityEngine, we can show and design a 3D reality in Johar Baru.

Instability mechanisms and evolution of a rocky cliff on the Atlantic coast of Spain

Predicting the response of rocky coasts to different erosional agents remains a great challenge at present. The episodic and discontinuous nature of the instability processes typical of hard bedrocks makes it difficult to make predictions based on observations over short research periods. This work aims to contribute to the understanding of the geomorphological evolution of rocky cliffs by means of a case study of a geologically complex cliff (developed on quartzite and slate) located on the Atlantic coast of Spain. The analysis of high-precision topographic models and orthophotographs, the use of geomatics techniques and geomorphological characterization have made it possible to define a model of the cliff behaviour. The results indicate that the structure of the bedrock determines the type of instability processes affecting the cliff and the morphology of the associated deposits. Lithology is the other main conditioning factor: while slate is easily eroded, quartzite offers greater strength and its detached blocks act as an effective natural defence element protecting the cliff and slowing down the coastal retreat. The evolution model established for this cliff explains the absence of retreat in the study period (2003–2022) and confirms the important role of local factors in cliff evolution.

3D Data Fusion for Historical Analyses of Heritage Buildings Using Thermal Images: The Palacio de Colomina as a Case Study

In the framework of built heritage monitoring techniques, a prominent position is occupied by thermography, which represents an efficient and non-invasive solution for these kinds of investigations, allowing the identification of phenomena detectable only in the non-visible range of the electromagnetic spectrum. This is of extreme interest, especially considering the possibility of integrating the radiometric information with the 3D models achievable from laser scanning or photogrammetric techniques, characterised by a high spatial resolution. This paper aims to illustrate how combining different geomatics techniques (in particular, by merging thermal images, laser scanning point clouds, and traditional visible colour photogrammetric data) can efficiently support historical analyses for studying heritage buildings. Additionally, a strategy for generating HBIM models starting from the integration of 3D thermal investigations and historical sources is proposed, concerning both the multi-temporal modification of the volumes of the building and the individual architectural elements. The case study analysed for the current research was the Palacio de Colomina in Valencia, Spain, a noble palace—now the headquarters of a university—that, during the last few centuries, has been subjected to considerable transformations in terms of rehabilitation works and modification of its volume.

Reconstruction of a real-world car-to-pedestrian collision using geomatics techniques and numerical simulations

The aim of this study is to provide an improved method for traffic accident reconstruction based on geomatics techniques and numerical simulations. A combination of various techniques was used. First, an unmanned aerial vehicle (UAV), laser scanner and structured-light scanner were used to obtain information on the accident scene, vehicle and victim. The collected traces provided detailed initial impact conditions for subsequent numerical simulations. Then, multi-body system (MBS) simulations were conducted to reconstruct the kinematics of the car-to-pedestrian collision. Finally, a finite element (FE) simulation using the THUMS model was performed to predict injuries. A real-life vehicle-pedestrian collision was used to verify the feasibility and effectiveness of this method. The reconstruction result revealed that the kinematic and injury predictions of the numerical simulations effectively conformed to the surveillance video and investigation of the actual accident. UAV photogrammetry was demonstrated to be more efficient in accident data collection than hand sketch and measurement, and 3D laser scanning enabled an easier and more accurate modeling process of vehicle. The present study shows the feasibility of this method for use in traffic accident reconstruction.

Historic gardens restoration – preliminary outcomes from a synergistic application of visual assessment and geomatic techniques to optimize the management of arboreal heritages

ISHS VIII International Conference on Landscape and Urban Horticulture Historic gardens restoration – preliminary outcomes from a synergistic application of visual assessment and geomatic techniques to optimize the management of arboreal heritages

THE USE OF OPEN SOURCE SOFTWARE FOR MONITORING BEE DIVERSITY IN NATURAL SYSTEMS: THE BEEMS PROJECT

Abstract. This work wants to highlight the results obtained during the BEEMS (Monitoring Bee Diversity in Natural System) project, which the main goal was to answer the following question: Which biotic and abiotic indicators of floral and nesting resources best reflect the diversity of bee species and community composition in the Israeli natural environment? The research was oriented towards the cost-effectiveness analysis of new aerial geomatics techniques and classical ground-based methods for collecting the indicators described above, based only on open-source software for data analysis. Two complementary study systems in central Israel have been considered: the Alexander Stream National Park, an area undergoing an ecological restoration project in a sandy ecosystem, and the Judean foothills area, to the South of Tel Aviv. In each study system, different surveys of bees, flowers, nesting substrates and soil, using classical field measurement methods have been conducted. Simultaneously, an integrated aero photogrammetric survey, acquiring different spectral responses of the land surface by means of Uncrewed Aerial Vehicle (UAV) imaging systems have been performed. The multispectral sensors have provided surface spectral response out of the visible spectrum, while the photogrammetric reconstruction has provided three-dimensional information. Thanks to Artificial Intelligence algorithms and the richness of the data acquired, a methodology for Land Cover Classification has been developed. The results obtained by ground surveys and advanced geomatics tools have been compared and overlapped. The results are promising and show a good fit between the two approaches, and high performance of the geomatics tools in providing valuable ecological data.

A Geomatic Approach to the Preservation and 3D Communication of Urban Cultural Heritage for the History of the City: The Journey of Napoleon in Venice

The use of historical maps in a digital environment can give considerable support to the study of the history of cities. It allows you to combine information from different sources, processed according to different geomatic techniques, to provide a reconstruction of urban configurations of the past and their comparison with iconographic and textual documentation of the same period. The aim of the research is to try to make the knowledge of a historical event easily accessible by converging within a simple model the various sources on which the reconstruction itself is based. This paper deals with the reconstruction of the ephemeral architecture created for Napoleon’s visit to Venice through the generation of 3D virtual models. The reconstruction was approached through a rigorous method, inserting these models into the context for which they were conceived. The generation of the historical city model, taking advantage of the algorithms of structure from motion applied to photogrammetry, made it possible to compare it with what was shown by the old paintings depicting the event. Virtual models processed within the GIS environment have been uploaded online thanks to the use of WebGIS. We chose to share the research results on the internet to allow users to avail themselves of a space that no longer exists from within it, going beyond the pictorial images of the past, overcoming communication through rendering and videos. The simultaneous application of methods and techniques related to the various components of geomatics within the digital environment has enabled the operation of a faithful reconstruction of reality, bringing to light past urban scenarios that no longer exist and are only known through paintings.

Integration of Laser Scanner, Ground-Penetrating Radar, 3D Models and Mixed Reality for Artistic, Archaeological and Cultural Heritage Dissemination

Three-dimensional digital acquisition techniques can be useful in archaeology because they make a further technological contribution to the visualization of finds and structures. The possibility of integrating three-dimensional models from different acquisition systems (laser scanner, UAV, reflex and Georadar) is even more exciting. One of the peculiarities of these integration techniques is the possibility of promoting the dissemination of knowledge through virtual reality, augmented reality and mixed reality, given the widespread use of mobile devices. This does not mean, of course, that with the mere creation of a 3D model (and allowing it to be viewed in 3D), the public automatically obtains more information about heritage. In fact, visiting a cultural heritage site in person allows one to receive much more information on finds and structures. However, if this is not possible, technologies that use 3D Virtual Reality help to provide a small knowledge base to those who cannot use the museum. We underline the importance of an integrated visualization from an archaeological and architectural perspective to obtain understanding of the structure with the integration of the two models with different data. The work that we present is part of a multidisciplinary project to recover and disseminate information about the Reggio Calabria’s (southern Italy) artistic, archaeological and cultural heritage. This work’s goal is the realization of a unique 3D model of the church “Madonna dei Poveri” (3D model of a buried part with 3D model of visible parts) by combining different geomatics techniques to show and investigate the interior and exterior parts (3D model obtained by laser scanner and photogrammetry), and the underground crypts (3D model obtained by Georadar), which are lying below the present surface and are no longer accessible due to coverage by post-depositional processes (Georadar). Finally, an app (using augmented reality and virtual reality) and a first experimentation of Mixed Reality is developed for the dissemination of the archaeological and cultural heritage information on the area of interest.

Estimation of the Block Adjustment Error in UAV Photogrammetric Flights in Flat Areas

UAV-DAP (unmanned aerial vehicle-digital aerial photogrammetry) has become one of the most widely used geomatics techniques in the last decade due to its low cost and capacity to generate high-density point clouds, thus demonstrating its great potential for delivering high-precision products with a spatial resolution of centimetres. The questions is, how should it be applied to obtain the best results? This research explores different flat scenarios to analyse the accuracy of this type of survey based on photogrammetric SfM (structure from motion) technology, flight planning with ground control points (GCPs), and the combination of forward and cross strips, up to the point of processing. The RMSE (root mean square error) is analysed for each scenario to verify the quality of the results. An equation is adjusted to estimate the a priori accuracy of the photogrammetric survey with digital sensors, identifying the best option for μxyz (weight coefficients depending on the layout of both the GCP and the image network) for the four scenarios studied. The UAV flights were made in Lorca (Murcia, Spain). The study area has an extension of 80 ha, which was divided into four blocks. The GCPs and checkpoints (ChPs) were measured using dual-frequency GNSS (global navigation satellite system), with a tripod and centring system on the mark at the indicated point. The photographs were post-processed using the Agisoft Metashape Professional software (64 bits). The flights were made with two multirotor UAVs, a Phantom 3 Professional and an Inspire 2, with a Zenmuse X5S camera. We verify the influence by including additional forward and/or cross strips combined with four GCPs in the corners, plus one additional GCP in the centre, in order to obtain better photogrammetric adjustments based on the preliminary flight planning.

INTEGRATION OF GEOMATIC TECHNIQUES FOR THE 3D REPRESENTATION AND MONITORING OF A VETERAN CHESTNUT TREE

Abstract. This study concerns the application of different geomatic techniques in forestry sector. An accurate 3D model of a veteran chestnut tree (Castanea sativa Mill.) has been realised integrating point clouds by Mobile Laser Scanner (MLS) and photogrammetry techniques. The surveys were conducted in two seasons (summer time: July 22nd 2021; autumn time: December 10th 2021), since chestnut is a deciduous tree and thus taking the chance to detect it also without leaves. Therefore, it was obtained tree’s metric data such as the diameter at breast height (DBH), the total height (TH), the crown basal area, the wood and crown volume. Annual surveys will result in a dataset of virtual trees that will be used to monitor the evolution of these noteworthy plants through time, which are expected to be considered as cultural heritage, given their story and their importance at regional and landscape level. The 3D model was then released for virtualization, making it accessible and available as a data container for different users. Such data will also provide historical memory about the presence of these veteran trees that might be lost in the future if affected by species-specific phytopathologies such as Ink Disease (Phytophthora spp.).