Photogrammetric Technology Research Articles

Evaluation of Vegetation Health in the PT X Reclamation Area Using the NDVI Method Based on Unmanned Aerial Vehicle (UAV) Multispectral Orthophoto Data

Abstract According to the International Energy Agency (IEA) in 2023, Indonesia became the third-largest coal-producing country globally after China and India. Indonesia’s coal production amounted to 775.2 million tons in 2023, and around 27% was used for domestic needs. Coal mining in Indonesia generally uses an open-pit mining system, which impacts changes in land cover, landscape form, and the loss of flora and fauna. To dismiss this stigma, good mining practices must be applied in every process to ensure the balance of post-mining land’s natural and social functions. One effort to restore the condition of post-mining land is revegetation. Revegetation activities on ex-mining land require much time, money, and energy, so the planted vegetation must be monitored and evaluated. The problem often encountered when using Landsat and Sentinel satellite image data is that clouds cover many areas because the island of Kalimantan has a tropical climate with high rainfall, humidity, and temperature throughout the year. Then, using multispectral aerial photography data is one solution for monitoring plant health. With the advancement of photogrammetric technology using multispectral cameras, it is possible to analyze the health of reclaimed plants using the NDVI method. The results of the NDVI analysis on reclaimed plants produced the highest index value of 0.877 and the lowest value of 0.013. With very healthy plant criteria covering 12.47 ha (71.5%), healthy plant criteria covering 4.95 ha (28.4%), and unhealthy criteria covering 0.02 ha (0.1%).

Synergia danych fotogrametrycznych uzyskanych na podstawie zdjęć naziemnych oraz UAV

Methods of short-range digital photogrammetry and unmanned aerial vehicle imagining increasingly find more extensive usage in various types of measurements. In recent years, modern photogrammetric technologies have found wide application in recreating 3D models of any objects. The resulting 3D models can be a source of information that may be used for measurement, inventorying and cataloguing, as well as for visualisation purposes. New methods of acquiring spatial data have been developed, such as laser scanning, imaging using unmanned aerial vehicles or digital non-metric cameras. Synergy and the confluence of these data have expanded the existing measurement possibilities, finding application in 3D modelling, inventorying of monuments, or monument conservation. Photogrammetric methods are comparable to direct measurement methods in terms of their accuracy, as well as speed and cost. They have a number of advantages, including a shortened time required for taking a photo, which is greatly convenient when measuring moving objects. Other advantages of photogrammetric methods include the possibility of development and performing measurements in chamber conditions and the lack of restrictions pertaining to repeating the measurement when errors are found or a need arises to supplement them [Kurczyński and Preuss 2000]. One of the possibilities offered by photogrammetry is the ability to create 3D visualizations. The creation of a three-dimensional model facilitates presenting the inventoried object in a realistic, complete, and up-to-date manner. This paper presents an attempt to synergise data for modelling a three-dimensional architectural object based on photos obtained with the Nikon D7500 non-metric camera and with the DJI Mavic Air unmanned aerial vehicle.

Scan-to-BIM Process and Architectural Conservation: Towards an Effective Tool for the Thematic Mapping of Decay and Alteration Phenomena

Ancient monumental complexes need continuous analysis and monitoring operations to preserve a good conservation status. For this reason, the analysis of decay and alteration phenomena represents one of the main activities for their preservation. At the same time, the diffusion of Heritage Building Information Modelling (HBIM) methodology opens new scenarios for the management of Architectural Heritage. The paper describes the workflow based on a Scan-to-BIM approach for the generation of a decay map in an HBIM model. The workflow was applied to a significant case study, the church of “Santa Maria della Grotta” in Marsala (Italy). This church, partially excavated in a sandstone bank, is part of a larger heritage site consisting of a series of hypogea and a Punic necropolis dating back more than a thousand years. The Scan-to-BIM process, relying on an integrated survey combining mobile laser scanning and photogrammetric technologies, enabled the achievement of a complete 3D parametric model of the monument and, altogether, a detailed decay map in a BIM environment. The mapping process focused on the production of thematic maps of perimetral walls according to an abacus of decays implemented in a BIM system, useful for the analysis and conservation of the church. The work demonstrates how the Scan-to-BIM process is an efficient approach for 3D data collection and how it could facilitate the identification and mapping of pathogenic phenomena. Furthermore, the inclusion of this kind of information in the BIM model represents an effective tool for the maintenance and restoration of built heritage.

VR running system using redirected walking technique

This study presents a novel virtual reality (VR) running system designed to allow users to simulate the experience of running outdoors while exercising indoors. This is achieved through the use of a head-mounted display (HMD), providing users with a immersive running experience at their convenience. The proposed system has three main functions: a redirected walking technique to map the direction of movement between real and virtual spaces, a virtual nose and Meta Quest 2 Guardian function to prevent VR sickness, and 3D CG models using photogrammetric technology to enhance the sensation of running outdoors. The results of an experimental evaluation of 17 participants demonstrated that approximately half felt the sensation of running; however more than 60% felt VR sickness while using the system. Subsequent exploratory experiments suggested that the Space Sense function of Meta Quest 2 could improve VR sickness. Despite numerous studies on walking with HMDs, to our knowledge, this is the first study on running in relatively small spaces, and the findings offer insights into future improvements and developments in this field.

Morphometric Parameters of the Water Bodies of Bagry Wielkie and Bagry Małe in the Biodiversity Context

The article presents the results of nature-based and geodetic query of two neighbouring endorheic borrow pits, i.e., Bagry Wielkie and Staw Płaszowski (Bagry Małe), situated almost in the centre of the Krakow city. The movements of water tables in 2016–2023 were observed (from the moment of ecological disaster in the Staw Płaszowski, in February 2016) and bathymetric maps were presented. Based on geodetic measurements carried out in 2016–2022 and direct observations of nature, documenting biodiversity of both reservoirs in 2019–2022, the authors reviewed the state of biosphere in this location. Surveying, observations and interviews allowed parameterization of both water bodies (morphometric data and bathymetric maps) and creating up-to-date database (location on maps, qualitative and quantitative elements of flora and fauna). The material makes base for further studies with the application of more advanced photogrammetric technologies and UAV technologies, which can make data contained in this publication more accurate.

A deep learning-based local feature extraction method for improved image matching and surface reconstruction from Yutu-2 PCAM images on the Moon

Topographic reconstruction of the lunar surface or other planets is important to engineering applications and scientific research in a planetary exploration mission. The typical methods of terrain reconstruction are usually based on photogrammetry techniques. Structure-from-Motion (SfM) is one of the most effective and commonly used photogrammetric technologies that estimate three-dimensional structures from two-dimensional image sequences. To find correspondences and align photos, SfM approaches require invariant features, such as Scale Invariant Feature Transform (SIFT). The hand-crafted features, however, seriously degrade performance due to weak texture and low light conditions causing image matching failure, which will directly affect the accuracy and robustness of reconstruction. Robust local descriptors based on deep learning outperform hand-crafted descriptors since convolutional neural networks are more robust than hand-engineered representations. Therefore, a novel and robust deep learning-based local feature extraction method is proposed, comprising two branch networks integrated with attention mechanisms for generating reliable keypoints and descriptors, respectively. Furthermore, a 3D terrain surface reconstruction workflow is constructed by combining it with the modern advanced image matching method and SfM system. The effectiveness of the proposed method and the workflow were verified in experiments using Panoramic Camera (PCAM) images acquired from three waypoints explored by the Yutu-2 lunar rover during the Chang’e-4 mission. We also illustrate how our approach supports other applications, such as creating panoramic mosaics of surface imagery. This provides a new and powerful method for planetary terrain reconstruction at a high spatial resolution that can meet the requirements for rover navigation and positioning, as well as geological analysis of the Moon and other planets. The source codes developed in this study are openly available at https://github.com/Atypical-Programmer/Deep_Reconstruction_Workflow.

THE FEATURES OF AERIAL PHOTOGRAPHY FOR ROAD REPAIR OR RECONSTRUCTION

This study formulates some of the actual problems that arise during engineering and geodetic survey for designing road repair and reconstruction. An analysis of the regulatory requirements currently in force in Ukraine for carrying out this type of work has been carried out, it has also been concluded that at present they do not keep up with the latest technologies. Studied publications describing the use of unmanned aerial vehicles (UAV). Classified navigation satellite receivers are installed on UAVs, for the purpose of determining coordinates. Particular attention is paid to the installation on the carrier of geodetic class navigation equipment using kinematic GNSS (Global Navigation Satellite System) technologies, such as RTK (Real-Time Kinematic) and PPK (Post-Processing Kinematic). These technologies allow us to determine the spatial coordinates of the centers of photos at the time of photographing with centimeter accuracy, which greatly simplifies the adjustment of digital photogrammetric models and increases their accuracy. But the most important advantage is a significant reduction in field surveying, which makes them less expensive and more efficient overall. In the course of the study, it was found that in conditions of limited access to nearby territories, insufficient stability of the results of determining the centers of images can affect the final quality of products. For cases where the maximum achievable accuracy is at the limit of the possibility of photogrammetric technology, the removal of the most critical elements is proposed to be combined by combining aerial photography technologies with ground technologies. The road’s hard surface surveying can be performed by ground geodetic methods (tacheometric or GNSS), and by modern laser scanning. At the same time, the adjacent territory, regarding the shooting of elements of which less stringent requirements are established, can be worked out by aerial photography. In further studies, it is necessary to determine the conditions for achieving the maximum accuracy of UAV photogrammetry. Keywords: aerial photography, photogrammetry, geodetic survey, reconstruction of highways.

Rill formation and evolution caused by upslope inflow and sediment deposition on freshly tilled loose surfaces

Rill erosion easily occurs on tilled surfaces because the soil shear resistance is less than the runoff shear stress. However, rill erosion formation and evolution on tilled surfaces under upslope inflow conditions remain unclear. The objective of this study was to investigate the rill formation process and rill erosion amount on tilled surfaces via flow scouring under different inflow rates (4, 6, and 8 L min−1) at a 15° slope. Close-range photogrammetric technology was applied to measure the rill morphology during the experiments. The results suggested that the rill formation process due to inflow could be divided into two distinct stages, namely, before and after runoff reached the downslope end, i.e., stages I and II, respectively. At stage I, runoff washed soil particles along the downslope direction. In this process, due to limited transport capacity of runoff, washed soil particles were deposited at the runoff head and formed a soil mound, which blocked the flow path, after which the runoff direction changed within the 6.7°− 50.6° range with an average moving distance of 0.62 m. As a result, a curved rill and a series of soil mounds were left on the surface. The inflow rate affected rill morphology by influencing the runoff direction change angle and runoff moving distance between the mounds on the surface. Herein, the rill formation process is referred to as downslope-trending erosion by inflow (DTEI). At stage II, runoff reached the downslope end, and a rill channel was formed throughout the slope. Thereafter, DTEI was largely reduced, and headward erosion was strengthened. As a result, the rill morphology quickly changed, such as the rill depth and rill width, which gradually increased with ongoing headward erosion. During DTEI, the rill paths were curved due to sediment deposition, and the sediment deposition conditions varied under the different inflow rates. Therefore, the rill curvature (RC) differed (1.039 ± 0.014). The RC decreased with headward erosion progression at stage II. The total sediment yield (TSY) increased with increasing inflow rate. Under inflow rates ranging from 4 to 6 L min−1 and 6–8 L min−1, the TSY increased 2.1–2.4 times. Consequently, DTEI on tilled surfaces significantly affects the initial rill morphology and evolution at the later stage. Hence, on slopes, its role should be considered in rill erosion assessment.

Classification of 3D UAS-SfM Point Clouds in the Urban Environment

The classification of three-dimensional (3D) point clouds derived through the use of cost-effective and time-efficient photogrammetric technologies can provide helpful information for applications, particularly in the mapping context. This paper presents a practical study of 3D Unmanned Aerial System (UAS) – Structure-from-Motion (SfM) point cloud classification using mainly open-source software. Following a supervised classification approach that makes use of only the dimensionality of points, the entire scene was classified into three land-cover categories: ground, high vegetation, and buildings. By applying the above-mentioned approach, the level of competence in classifying a 3D point cloud of a heterogeneous scene situated in the University of KwaZulu-Natal, South Africa, was evaluated. The resulting overall classification accuracy of 81.3%, with a Kappa coefficient of 0.70, was determined by means of a confusion matrix. The results achieved indicate the potential use of open-source software and 3D UAS-SfM point cloud classification in mapping and monitoring complex environments and in other applications that might arise.

MULTISPECTRAL UAV DATA ENHANCING THE KNOWLEDGE OF LANDSCAPE HERITAGE

Abstract. Landscape heritage, especially if it does not arouse great public echoes, needs great attention, starting from knowledge and metric documentation processes to which reality-based sensing techniques often contribute significantly. The primary purpose of this work is to reflect on the possibility of identifying submerged built heritages, which are sometimes characterised by precarious safety conditions due to abandonment, through multispectral photogrammetric technologies with primary data acquired by UAVs. The experience carried out in an impervious alpine territory foresees the close relationship of integration of photogrammetric techniques in the visible and the multispectral ranges, with the integration of terrestrial scanning solutions from slam-based mobile systems, to validate the results provided by the analysis of the spectral signatures of different kind of soils.

3D PHOTOGRAMMETRY MODELING FOR SAFETY MONITORING OF FORTRESS WALLS

Abstract. In the monitoring to prevent collapse or tipping in the structure of linear-shaped fortress walls, the record of shapes like slope or protrusion is very important(Jo and Hong, 2019). As the way to record the shapes, laser scan or photogrammetric technology is employed. A laser scan that has to install several points of measurement has a limitation in recording them if the terrain is undulating, or the structure becomes huge. Photogrammetry has a shortening effect in terms of cost and process (Kim, 2020) compared to that.This study examined a measure for producing a 3D mesh model with aerial and ground photography for fortress walls. In addition, this study tested if it would be possible to monitor the slope and protrusion, etc. of fortress walls. This study tested the accuracy of the model produced with photogrammetry to use in the diagnosis and monitoring of the structural safety of fortress walls.The research subject was Korea’s cultural heritage, Seosan Haemieupseong Fortress, and a model was produced for the section about 100m of the fortress walls.The positional accuracy, elevation/section accuracy, LOD, and texture joint precision of two models (Model A & Model B) produced with photogrammetry and laser scan were compared.This study revealed that the model produced at LOD Level 4 would be effective for monitoring the displacement since it could measure the shape, curvature, and slope of stones of the fortress walls.

NORMAL AND CONVERGENT METHODS OF SURVEY FOR INVENTORY AND CERTIFICATION OF CULTURAL STRUCTURES

The article aims to study the use of normal and convergent stereo-photographic techniques to determine physical condition of a building, to compare errors obtained using a digital non-specialized camera, and use these methods in the inventory and certification of real estate. Monitoring architectural monuments is currently one of the most urgent problems. The development of large cities in which architectural monuments are under threat of destruction requires modern and effective technology for monitoring which is possible using low-cost photogrammetry methods: digital images and cheap software. The development of digital cameras into terrestrial photogrammetry resulted in fundamentally new methods and photogrammetric technologies. In case of monitoring objects of small sizes, such as architectural monuments, the cost of shooting equipment is one of the most significant factors, which reduces the cost of work, therefore, in the vast majority of cases, only digital non-metric cameras are used for shooting. The most significant problem is the calibration of digital non-metric cameras. Currently, a huge number of options for calibrating digital cameras have been developed. These options differ in calibration method, type of test object, type of mathematical model for accounting for distortion (algebraic, physical or hybrid model) The present study how that accuracy of the convergent method is almost 2 times higher than that of the normal photogrammetric survey method and provides a large survey overlap area. Comparing all the indicators and characteristics of these methods, we concluded the feasibility, high profitability, and low complexity of the convergent method of stereo photography to perform inventory and certification of real estate. We found that when surveying building using convergent method it is necessary to use 2 times fewer stations than when surveying by normal method. Thus, the convergent method is 2 times faster and more efficiently.

Recognising Decorative Elements Taken from the West in Qajar Period Façades Using Close-Range Photogrammetric Technology: the Case of Window-Pediments in the Ahmad Shahi Pavilion

یکی از مهم‌ترین آرایه‌های نما‌‌های قاجاری پنجرة سنتوری است که در اروپا با اشکال مختلف ساده، منحنی، و شکسته از دوران رم کلاسیک تا دوران نئوکلاسیک در نماسازی به کار رفته است و در جداره‌‌های برون‌گرای دورة قاجار با تأثیر از معماری غربی رواج یافته است. در پژوهش‌های اندکی به مطالعة این عنصر وارداتی و ویژگی‌های متمایز قاجاری آن به نسبت نمونه‌‌های غربی پرداخته شده است. در این پژوهش با هدف بازشناسی پنجرة سنتوری با روش تک‌نگاری، کوشک احمدشاهی کاخ نیاوران با 23 قاب متنوع مزین به سنتوری انتخاب و با ابزار فتوگرامتری برد کوتاه مستندنگاری دقیق شده است. هدف از این پژوهش بررسی این آرایة غربی و تأثیرات بومی معماری دورة قاجار و تغییرات آن در یک مورد منتخب است. بنابر یافته‌‌ها سه نوع سنتوری مثلثی ساده، شکستة طوماری، و شکستة مارپیچ در جداره‌‌ها به کار رفته است که، با در نظر گرفتن دو خصیصة شکل و بافت پرکنندة سینة سنتوری، در کل به 16 نوع مختلف دارای الگوی قرارگیری ویژه دسته‌بندی می‌شود. سنتوری‌های جفت و سنتوری‌های طرفین تقسیمات سه‌تایی یا پنج تایی مشابهند. سنتوری طرفین پلکان ورودی مفصل‌ترین نمونه و دارای رأس آجر برش‌خورده به شکل گل و گلدانی است. در این پژوهش نتیجه گرفته شده است که خلاقیت و بداهه‌سازی در تغییر شکل سنتوری الگوی تزیین سینة سنتوری و بافت پرکنندة آن با استفاده از هنر آجرکاری منقوش و قالبی وجه تمایز اثر معماران دورة قاجار در این بناست. بدین‌ترتیب با آجر، که مصالح غالب و سرمنشأ آرایه‌های مختلفی در تاریخ معماری ایران است، این عنصر وارداتی با اشکال متنوع بازتولید شده است.

A clipping algorithm for real-scene 3D models

ABSTRACT The development of unmanned aerial vehicle (UAV) oblique photogrammetric technology provides a good foundation for the rapid construction of large-scale and high-definition real-scene 3D models. However, due to the limitations of the modeling process, irrelevant feature data cannot be eliminated in the modeling stage. The built models contain irrelevant features and model distortions caused by errors. At present, most existing clipping algorithms cannot effectively clip real-scene 3D models that are organized as a whole or with levels of detail (LODs). Therefore, this paper proposes a novel algorithm for clipping real-scene 3D models from any perspective based on clipping boundary lines that fit the surfaces of the models. The results of the clipping experiments for 3D models constructed with oblique UAV images show that this algorithm can effectively clip any part of the 3D models, that the clipping results of each level model closely fit the corresponding clipping boundary lines, and that the accuracy of the clipping results is very high. Additionally, the time complexity of the algorithm is O(n 2). In conclusion, the algorithm proposed in this paper provides correct and effective clipping results for real-scene 3D models with LODs that are constructed with photogrammetric or 3D laser scanning data.

Validity and reliability of three-dimensional modeling of orthodontic dental casts using smartphone-based photogrammetric technology

The development of intraoral scanning technology has effectively enhanced the digital documentation of orthodontic dental casts. Albeit, the expense of this technology is the main limitation. The purpose of the present study was to assess the validity and reliability of virtual three-dimensional (3D) models of orthodontic dental casts, which were constructed using smartphone-based 3D photogrammetry. A smartphone was used to capture a set of two-dimensional images for 30 orthodontic dental casts. The captured images were processed to construct 3D virtual images using Agisoft and 3DF Zephyr software programs. To evaluate the accuracy of the virtual 3D models obtained by the two software programs, the virtual 3D models were compared with cone-beam computed tomography scans of the 30 dental casts. Colored maps were used to express the absolute distances between the points of each compared two surfaces; then, the means of the 100%, 95th, and 90th of the absolute distances were calculated. A Wilcoxon signed-rank test was applied to detect any significant differences. The differences between the constructed 3D images and the cone-beam computed tomography scans were not statistically significant and were accepted clinically. The deviations were mostly in the interproximal areas and in the occlusal details (sharp cusps and deep pits and fissures). This study found that smartphone-based stereophotogrammetry is an accurate and reliable method for 3D modeling of orthodontic dental casts, with errors less than the accepted clinically detectable error of 0.5 mm. Smartphone photogrammetry succeeded in presenting occlusal details, but it was difficult to accurately reproduce interproximal areas.

Cloner 3D photogrammetric facial scanner: Assessment of accuracy in a controlled clinical study.

To evaluate the accuracy of facial measurements on three-dimensional images obtained using a new photogrammetric scanner. A total of 11 participants were included in the study. Nine customized adhesive labels were used to identify the facial landmarks: Trichion (Tri), Glabella (G), Right (Exr) and Left (Exl), Pronasal (Pn), Subnasal (Sn), Chelion right (Chr) and left (Chl) and Mentonian (Me). Two trained and calibrated examiners were responsible for performing seven linear measurements for each participant (Tri-G, Sn-Me, Exr-Exl, Chr-Chl, Exr-Chr, Exl-Chl, Pn-Sn) first with a digital caliper and later with a three-dimensional model obtained after digitalization with photogrammetric technology. The intraclass correlation coefficient (ICC), mean difference, SD, and Bland-Altman correlation were used to compare the measurements performed. Intra and inter-examiner reliability were excellent (ICC >0.9). In general, the measurements presented a variation of a minor 2.0 mm. However, only three measures (Sn-Me, Exr-Exl, and Exr-Chr) were outside the clinical acceptability range. The 3D Cloner scanner showed clinically acceptable accuracy comparable to the digital caliper with a variation of -0.8 ± 1.2 mm. Inter- and intra-examiner agreement on digital measurements was also observed. Scanners with accurate 3D model reproductions associated with reliable digital measurements provide a more precise diagnosis and better planning in orofacial treatment.

Accuracy of photogrammetric technologies for the scanning of dental models: A systematic review

Background: Traditional dental scanners require a heavy investment, representing a high barrier of entry into digital dentistry. Photogrammetric-based scanners may represent an affordable cost-effective alternative to traditional dental scanners used for the digitalization of plaster models. Photogrammetry is the science of extracting 3D information from photographs. The process involves taking overlapping photographs of an object or space and converting them into 2D or 3D digital models. Objective: This review aimed to identify and appraise the reported accuracy of photogrammetric-generated digital dental models. Materials and methods: A search strategy was applied in 3 databases (Medline, Web of Science and Scopus), from Feb 1 2021 to Dec 1 2021, the search was limited to articles in English published in the last 5 years about studies evaluating the dimensional accuracy of 3-dimensional digital models acquired by the scanning of plaster models with photogrammetric technologies. Results: Two independent reviewers screened 75 records on basis of titles and abstracts for assessment against the inclusion criteria for the review, 4 articles were deemed eligible, the risk of bias for the selected articles was measured, data extraction was performed by only one author. Conclusion: With today’s technology, based on the four studies evaluated, we conclude that photogrammetric-generated digital models while lacking accuracy for incorporation into the treatment flow, in the future it could be used for diagnostic, planning, and achieving.

Airborne combined photogrammetry—infrared thermography applied to landslide remote monitoring

The combination between two remote surveying methods is presented herein as a pioneering approach for landslide airborne monitoring. The survey of an active landslide by UAV-based RGB photogrammetry and infrared thermography, sided by the knowledge of the field condition, allowed increasing the scientific experience on the remote sensing of slope instability phenomena by analyzing multiple aspects related to the evolution of key slope features. In this research, the state and distribution of activity of a landslide was monitored by matching data arising from three-dimensional models of the slope, built by exploiting the aerial RGB photogrammetric technology, and thermal outcomes, resulting from the airborne application of infrared thermography principles. In this frame, thermal anomalies detected during different monitoring campaigns allowed recognizing peculiar features along the unstable slope that could be related to specific kinematic elements involved in the landslide activity. Forming cracks, developing scarps, wet terrain portions, and loose material are some of the elements that could be located by integrating thermal outcomes with Digital Surface Models of the slope. Thanks to the different thermal behavior of such elements, strengthened herein by a novel approach of thermal data processing (i.e. the study of thermal slope profiles), the lateral and retrogressive evolution of the studied movement was first hypothesized and then verified in field. Achieved results show that the location of thermal anomalies well corresponds to field structures, which sometimes are hardly detectable by in situ or RGB surveys, thus suggesting the high potential of the methodological approach developed for this study. The scientific validity of presented data gains relevance thanks to the positive field validation. This paves the way to further studies aimed at implementing the infrared aerial survey of landslides, which surely could bring benefits to practical applications in terms of survey speed and spatial coverage, especially in areas characterized by bad field logistics.

Two-Step Alignment of Mixed Reality Devices to Existing Building Data

With the emergence of XR technologies, the demand for new time- and cost-saving applications in the AEC industry based on these new technologies is rapidly increasing. Their real-time feedback and digital interaction in the field makes these systems very well suited for construction site monitoring, maintenance, project planning, and so on. However, the continuously changing environments of construction sites and facilities requires extraordinary robust and dynamic data acquisition technologies to capture and update the built environment. New XR devices already have the hardware to accomplish these tasks, but the framework to document and geolocate multi-temporal mappings of a changing environment is still very much the subject of ongoing research. The goal of this research is, therefore, to study whether Lidar and photogrammetric technologies can be adapted to process XR sensory data and align multiple time series in the same coordinate system. Given the sometimes drastic changes on sites, we do not only use the sensory data but also any preexisting remote sensing data and as-is or as-designed BIM to aid the registration. In this work, we specifically study the low-resolution geometry and image matching of the Hololens 2 during consecutive stages of a construction. During the experiments, multiple time series of constructions are captured and registered. The experiments show that XR-captured data can be reliably registered to preexisting datasets with an accuracy that matches or exceeds the resolution of the sensory data. These results indicate that this method is an excellent way to align generic XR devices to a wide variety of existing reference data.

A Non-destructive Method to Create a Time Series of Surface Area for Coral Using 3D Photogrammetry

The wax dip method typically used to determine the surface area of corals for data normalization is destructive, rendering the collection of time series for such data impossible. With recent advancements in photogrammetric technology, it is now possible to collect these data in a non-destructive manner at very high levels of accuracy. This photogrammetric method using Agisoft’s Metashape is compared to the standard wax-dip method using both objects of known surface area and objects of unknown surface area. Objects of known surface area (i.e., objects that have surface areas that can be calculated using geometrical formulas) were estimated with a similar degree of accuracy with the Photogrammetry (PG) method (R2 = 0.9922, slope = 0.9835) as with the wax-dip method (R2 = 0.9872, slope = 1). A single factor ANOVA confirmed that there was no significant difference between measurements from the three methods of geometrical calculation, wax dipping, or photogrammetry for objects of known surface area. This paper describes the methods for rapidly collecting surface area data of small to moderately sized coral nubbins in a laboratory setting and characterizes the relationship between buoyant weight and surface area over time for the coral species Stylophora pistillata. Finally, two predictive models are proposed to estimate surface area from weight in air measurements.