This page has only limited features, please log in for full access.

Prof. Andreas Georgopoulos
National Technical University of Athens

Basic Info


Research Keywords & Expertise

0 Automation
0 Geoinformatics
0 Cultural heritage documentation
0 Geomatics for cultural heritage
0 HBIM – heritage building information modeling

Honors and Awards

The user has no records in this section


Career Timeline

The user has no records in this section.


Short Biography

The user biography is not available.
Following
Followers
Co Authors
The list of users this user is following is empty.
Following: 0 users

Feed

Original article
Published: 10 May 2021 in PFG – Journal of Photogrammetry, Remote Sensing and Geoinformation Science
Reads 0
Downloads 0

The increasing need for accurate bathymetric mapping is essential for a plethora of offshore activities. Even though aerial image datasets through Structure from Motion (SfM) and Multi-View Stereo (MVS) techniques can provide a low-cost alternative compared to LiDAR and SONAR, offering additionally, important visual information, water refraction poses significant obstacles in delivering accurate bathymetry. In this article, the generation of manned and unmanned airborne synthetic datasets of dry and water covered areas is presented. These data are used to train models for correcting the geometric effects of refraction on real-world image-based point clouds and aerial images. Based on a thorough evaluation, important improvements are presented, indicating the increased accuracy and the reduced noise in the point clouds of the derived bathymetric products, meeting also the International Hydrographic Organization’s (IHO) standards.

ACS Style

Panagiotis Agrafiotis; Konstantinos Karantzalos; Andreas Georgopoulos; Dimitrios Skarlatos. Learning from Synthetic Data: Enhancing Refraction Correction Accuracy for Airborne Image-Based Bathymetric Mapping of Shallow Coastal Waters. PFG – Journal of Photogrammetry, Remote Sensing and Geoinformation Science 2021, 1 -19.

AMA Style

Panagiotis Agrafiotis, Konstantinos Karantzalos, Andreas Georgopoulos, Dimitrios Skarlatos. Learning from Synthetic Data: Enhancing Refraction Correction Accuracy for Airborne Image-Based Bathymetric Mapping of Shallow Coastal Waters. PFG – Journal of Photogrammetry, Remote Sensing and Geoinformation Science. 2021; ():1-19.

Chicago/Turabian Style

Panagiotis Agrafiotis; Konstantinos Karantzalos; Andreas Georgopoulos; Dimitrios Skarlatos. 2021. "Learning from Synthetic Data: Enhancing Refraction Correction Accuracy for Airborne Image-Based Bathymetric Mapping of Shallow Coastal Waters." PFG – Journal of Photogrammetry, Remote Sensing and Geoinformation Science , no. : 1-19.

Conference paper
Published: 14 April 2021 in Transactions on Petri Nets and Other Models of Concurrency XV
Reads 0
Downloads 0

The specific paper forms part of the Postdoctoral Research Project (Implemented by Athina Chroni, Dr. Archaeologist, supervised by Professor Andreas Georgopoulos, Laboratory of Photogrammetry-National Technical University of Athens.) focusing on Ioannina city’s Ottoman period (1430–1913) and its multicultural profile as depicted in buildings, public or private, religious or secular, conventional or more elaborate, each having its own historical and architectural interest. Unfortunately, most of the landmark buildings have been destroyed due to natural disasters, religious hatred and the unbridled, often uncontrolled modern constructions. However, the existence and form of several of those edifices survived thanks to fragmentary information of various kinds, while their location in the urban web and their dimensions can be clarified, in several cases, by their comparative studies with buildings recorded at the same representations whose location and dimensions are known or buildings preserved until today. Under this perspective, a variety of data like historiographic, bibliographic, archaeological, cartographic, topographic, remote sensing imagery, optical displays, travelers’ descriptions, other literary sources, local legends, inhabitants’ interviews have been collected, analyzed, cross-examined and digitally processed, thus leading to the development of a Geographic Information System, the 3D landmarks digital models, a web data base and QR tags at the specific sites, where the landmark buildings used to stand, thus connecting the intangible (digital) with the tangible (physical space) and achieving interaction of the project with the local community. Moreover, cultural walks within the city's urban web, related to the project’s axis are also proposed.

ACS Style

Athina Chroni; Andreas Georgopoulos. Documentation and 3D Digital Modelling: The Case of a Byzantine Christian Temple and an Ottoman Muslim Mosque in Ioannina City, Greece. Transactions on Petri Nets and Other Models of Concurrency XV 2021, 78 -89.

AMA Style

Athina Chroni, Andreas Georgopoulos. Documentation and 3D Digital Modelling: The Case of a Byzantine Christian Temple and an Ottoman Muslim Mosque in Ioannina City, Greece. Transactions on Petri Nets and Other Models of Concurrency XV. 2021; ():78-89.

Chicago/Turabian Style

Athina Chroni; Andreas Georgopoulos. 2021. "Documentation and 3D Digital Modelling: The Case of a Byzantine Christian Temple and an Ottoman Muslim Mosque in Ioannina City, Greece." Transactions on Petri Nets and Other Models of Concurrency XV , no. : 78-89.

Journal article
Published: 06 April 2021 in ISPRS International Journal of Geo-Information
Reads 0
Downloads 0

This paper presents an effective and semi-automated method for detecting 3D edges in 3D point clouds with the help of high-resolution digital images. The effort aims to contribute towards addressing the unsolved problem of automated production of vector drawings from 3D point clouds of cultural heritage objects. Edges are the simplest primitives to detect in an unorganized point cloud and an algorithm was developed to perform this task. The provided edges are defined and measured on 2D digital images of known orientation, and the algorithm determines the plane defined by the edge on the image and its perspective center. This is accomplished by applying suitable transformations to the image coordinates of the edge points based on the Analytical Geometry relationships and properties of planes in 3D space. This plane inevitably contains the 3D points of the edge in the point cloud. The algorithm then detects and isolates those points which define the edge in the world system. Finally, the goal is to reliably locate the points that describe the desired edge in their true position in the geodetic space, using several constraints. The algorithm is firstly investigated theoretically for its efficiency using simulation data and then assessed under real conditions and under different image orientations and lengths of the edge on the image. The results are presented and evaluated.

ACS Style

Maria Dolapsaki; Andreas Georgopoulos. Edge Detection in 3D Point Clouds Using Digital Images. ISPRS International Journal of Geo-Information 2021, 10, 229 .

AMA Style

Maria Dolapsaki, Andreas Georgopoulos. Edge Detection in 3D Point Clouds Using Digital Images. ISPRS International Journal of Geo-Information. 2021; 10 (4):229.

Chicago/Turabian Style

Maria Dolapsaki; Andreas Georgopoulos. 2021. "Edge Detection in 3D Point Clouds Using Digital Images." ISPRS International Journal of Geo-Information 10, no. 4: 229.

Journal article
Published: 10 March 2021 in Remote Sensing
Reads 0
Downloads 0

Conventional multi-view stereo (MVS) approaches based on photo-consistency measures are generally robust, yet often fail in calculating valid depth pixel estimates in low textured areas of the scene. In this study, a novel approach is proposed to tackle this challenge by leveraging semantic priors into a PatchMatch-based MVS in order to increase confidence and support depth and normal map estimation. Semantic class labels on image pixels are used to impose class-specific geometric constraints during multiview stereo, optimising the depth estimation on weakly supported, textureless areas, commonly present in urban scenarios of building facades, indoor scenes, or aerial datasets. Detecting dominant shapes, e.g., planes, with RANSAC, an adjusted cost function is introduced that combines and weighs both photometric and semantic scores propagating, thus, more accurate depth estimates. Being adaptive, it fills in apparent information gaps and smoothing local roughness in problematic regions while at the same time preserves important details. Experiments on benchmark and custom datasets demonstrate the effectiveness of the presented approach.

ACS Style

Elisavet Stathopoulou; Roberto Battisti; Dan Cernea; Fabio Remondino; Andreas Georgopoulos. Semantically Derived Geometric Constraints for MVS Reconstruction of Textureless Areas. Remote Sensing 2021, 13, 1053 .

AMA Style

Elisavet Stathopoulou, Roberto Battisti, Dan Cernea, Fabio Remondino, Andreas Georgopoulos. Semantically Derived Geometric Constraints for MVS Reconstruction of Textureless Areas. Remote Sensing. 2021; 13 (6):1053.

Chicago/Turabian Style

Elisavet Stathopoulou; Roberto Battisti; Dan Cernea; Fabio Remondino; Andreas Georgopoulos. 2021. "Semantically Derived Geometric Constraints for MVS Reconstruction of Textureless Areas." Remote Sensing 13, no. 6: 1053.

Journal article
Published: 28 January 2020 in Virtual Archaeology Review
Reads 0
Downloads 0

Archaeological restoration of monuments is a practice requiring extreme caution and thorough study. Archaeologists and conservation experts are very reluctant to proceed to restoration and indeed to reconstruction actions without detailed consultation and thought. Nowadays, anastylosis executed on the real object is practically prohibited. Contemporary technologies have provided archaeologists and other conservation experts with the tools to embark on virtual restorations or anastyloses, thus testing various alternatives without physical intervention on the monument itself. In this way, the values of the monuments are respected according to international conventions. In this paper, two such examples of virtual archaeological anastyloses of two important Macedonian tombs in northern Greece are presented. The anastyloses were performed on three-dimensional (3D) models which have been produced using modern digital 3D documentation techniques, such as image-based modelling and terrestrial laser scanning. The reader is introduced to the history and importance –as well as the peculiarities– of the Macedonian tombs. In addition, the two tombs are described in detail mainly from an archaeological point of view The process of field data acquisition and processing to produce the 3D models are described. Simple and more or less standard methods were employed in acquiring the raw data. Processing was carried out using commercial software. The resulting 3D models and other documentation products are assessed for their accuracy and completeness. The decisions for the virtual anastylosis are explained in detail and the actual process is also described. The restored monuments are presented and evaluated by the conservation experts. Thus, it is shown how important virtual anastylosis of monuments is to archaeological researchers, as it enables them to conduct in-depth studies, without actually tampering with the monuments themselves. Digital 3D models are contributing to many disciplines, especially in archaeology, as they enable a wider audience to easily access both archaeological and geometric information as well as offering a high degree of interaction possibilities.

ACS Style

Maria Stampouloglou; Olympia Toska; Sevi Tapinaki; Georgia Kontogianni; Margarita Skamantzari; Andreas Georgopoulos. Archaeological anastylosis of two Macedonian tombs in a 3D virtual environment. Virtual Archaeology Review 2020, 11, 26 -40.

AMA Style

Maria Stampouloglou, Olympia Toska, Sevi Tapinaki, Georgia Kontogianni, Margarita Skamantzari, Andreas Georgopoulos. Archaeological anastylosis of two Macedonian tombs in a 3D virtual environment. Virtual Archaeology Review. 2020; 11 (22):26-40.

Chicago/Turabian Style

Maria Stampouloglou; Olympia Toska; Sevi Tapinaki; Georgia Kontogianni; Margarita Skamantzari; Andreas Georgopoulos. 2020. "Archaeological anastylosis of two Macedonian tombs in a 3D virtual environment." Virtual Archaeology Review 11, no. 22: 26-40.

Journal article
Published: 18 January 2020 in Remote Sensing
Reads 0
Downloads 0

Although aerial image-based bathymetric mapping can provide, unlike acoustic or LiDAR (Light Detection and Ranging) sensors, both water depth and visual information, water refraction poses significant challenges for accurate depth estimation. In order to tackle this challenge, we propose an image correction methodology, which first exploits recent machine learning procedures that recover depth from image-based dense point clouds and then corrects refraction on the original imaging dataset. This way, the structure from motion (SfM) and multi-view stereo (MVS) processing pipelines are executed on a refraction-free set of aerial datasets, resulting in highly accurate bathymetric maps. Performed experiments and validation were based on datasets acquired during optimal sea state conditions and derived from four different test-sites characterized by excellent sea bottom visibility and textured seabed. Results demonstrated the high potential of our approach, both in terms of bathymetric accuracy, as well as texture and orthoimage quality.

ACS Style

Panagiotis Agrafiotis; Konstantinos Karantzalos; Andreas Georgopoulos; Dimitrios Skarlatos. Correcting Image Refraction: Towards Accurate Aerial Image-Based Bathymetry Mapping in Shallow Waters. Remote Sensing 2020, 12, 322 .

AMA Style

Panagiotis Agrafiotis, Konstantinos Karantzalos, Andreas Georgopoulos, Dimitrios Skarlatos. Correcting Image Refraction: Towards Accurate Aerial Image-Based Bathymetry Mapping in Shallow Waters. Remote Sensing. 2020; 12 (2):322.

Chicago/Turabian Style

Panagiotis Agrafiotis; Konstantinos Karantzalos; Andreas Georgopoulos; Dimitrios Skarlatos. 2020. "Correcting Image Refraction: Towards Accurate Aerial Image-Based Bathymetry Mapping in Shallow Waters." Remote Sensing 12, no. 2: 322.

Journal article
Published: 24 September 2019 in Remote Sensing
Reads 0
Downloads 0

The determination of accurate bathymetric information is a key element for near offshore activities; hydrological studies, such as coastal engineering applications, sedimentary processes, hydrographic surveying, archaeological mapping and biological research. Through structure from motion (SfM) and multi-view-stereo (MVS) techniques, aerial imagery can provide a low-cost alternative compared to bathymetric LiDAR (Light Detection and Ranging) surveys, as it offers additional important visual information and higher spatial resolution. Nevertheless, water refraction poses significant challenges on depth determination. Till now, this problem has been addressed through customized image-based refraction correction algorithms or by modifying the collinearity equation. In this article, in order to overcome the water refraction errors in a massive and accurate way, we employ machine learning tools, which are able to learn the systematic underestimation of the estimated depths. In particular, an SVR (support vector regression) model was developed, based on known depth observations from bathymetric LiDAR surveys, which is able to accurately recover bathymetry from point clouds derived from SfM-MVS procedures. Experimental results and validation were based on datasets derived from different test-sites, and demonstrated the high potential of our approach. Moreover, we exploited the fusion of LiDAR and image-based point clouds towards addressing challenges of both modalities in problematic areas.

ACS Style

Panagiotis Agrafiotis; Dimitrios Skarlatos; Andreas Georgopoulos; Konstantinos Karantzalos. DepthLearn: Learning to Correct the Refraction on Point Clouds Derived from Aerial Imagery for Accurate Dense Shallow Water Bathymetry Based on SVMs-Fusion with LiDAR Point Clouds. Remote Sensing 2019, 11, 2225 .

AMA Style

Panagiotis Agrafiotis, Dimitrios Skarlatos, Andreas Georgopoulos, Konstantinos Karantzalos. DepthLearn: Learning to Correct the Refraction on Point Clouds Derived from Aerial Imagery for Accurate Dense Shallow Water Bathymetry Based on SVMs-Fusion with LiDAR Point Clouds. Remote Sensing. 2019; 11 (19):2225.

Chicago/Turabian Style

Panagiotis Agrafiotis; Dimitrios Skarlatos; Andreas Georgopoulos; Konstantinos Karantzalos. 2019. "DepthLearn: Learning to Correct the Refraction on Point Clouds Derived from Aerial Imagery for Accurate Dense Shallow Water Bathymetry Based on SVMs-Fusion with LiDAR Point Clouds." Remote Sensing 11, no. 19: 2225.

Chapter
Published: 16 June 2018 in Heritage Preservation
Reads 0
Downloads 0

Nowadays, humanity feels obliged to maintain cultural heritage for our future generations. To that end, numerous experts are contributing. Contemporary technological advances, i.e. digital achievements, have helped a lot to this end. In this paper, these technological advances are briefly presented and explained. It is attempted to show how these advances may help cultural heritage if applied correctly and wisely. The argument is not how they will replace traditional documentation or conservation methods, but how they will support, enhance and supplement them for achieving the desired result with sensitivity and knowledge. The available digital documentation techniques are described along with the contemporary nondestructive techniques for cultural heritage pathology diagnosis and conservation. Their advantages are investigated along with their implementation actions. These techniques include image-based methodologies for producing three-dimensional models of which traditional two-dimensional products may be extracted, laser scanning techniques to acquire directly three-dimensional information from the object, nondestructive techniques in order to diagnose pathology problems, etc. In order to highlight these techniques, several examples are presented. The alternative uses of the contemporary digital techniques are highlighted through these examples. Among others, the following applications will be presented: The virtual restoration of a collapsed stone bridge, the virtual restoration of a monument exposed to the weather conditions and the development of a virtual museum are presented. Finally, a future outlook is attempted, in order to envisage the path that the implementation of these technological advances will lead the worldwide effort to document and preserve our cultural heritage.

ACS Style

Andreas Georgopoulos. Contemporary Digital Technologies at the Service of Cultural Heritage. Heritage Preservation 2018, 1 -20.

AMA Style

Andreas Georgopoulos. Contemporary Digital Technologies at the Service of Cultural Heritage. Heritage Preservation. 2018; ():1-20.

Chicago/Turabian Style

Andreas Georgopoulos. 2018. "Contemporary Digital Technologies at the Service of Cultural Heritage." Heritage Preservation , no. : 1-20.

Conference paper
Published: 13 March 2018 in Communications in Computer and Information Science
Reads 0
Downloads 0

Taking care of mankind’s cultural heritage is a well-established obligation to us and to our future generations. To that end numerous experts are contributing. Contemporary technological advances, i.e. digital achievements, have helped a lot to this end. In this paper these technological advances are briefly presented and explained. It is attempted to show how these advances may help Cultural heritage if applied correctly and wisely. The argument is not how they will replace traditional documentation or conservation methods, but how they will support, enhance and supplement them for achieving the desired result with sensitivity and knowledge. The available digital documentation techniques are described along with the contemporary non-destructive techniques for cultural heritage pathology diagnosis and conservation. Their advantages are investigated along with their implementation actions. These techniques include image based methodologies for producing three dimensional models of which traditional two-dimensional products may be extracted, laser scanning techniques to acquire directly three-dimensional information from the object, Nondestructive techniques in order to diagnose pathology problems etc. In order to highlight these techniques, several examples are presented. The alternative uses of the contemporary digital techniques are highlighted through these examples. Among others the following applications will be presented: The virtual restoration of a collapsed stone bridge, the virtual restoration of a monument exposed to the weather conditions and the development of a virtual museum are presented. Finally, a future outlook is attempted, in order to envisage the path that the implementation of these technological advances will lead the worldwide effort to document and preserve our cultural heritage.

ACS Style

Andreas Georgopoulos. CIPA’s Perspectives on Cultural Heritage. Communications in Computer and Information Science 2018, 215 -245.

AMA Style

Andreas Georgopoulos. CIPA’s Perspectives on Cultural Heritage. Communications in Computer and Information Science. 2018; ():215-245.

Chicago/Turabian Style

Andreas Georgopoulos. 2018. "CIPA’s Perspectives on Cultural Heritage." Communications in Computer and Information Science , no. : 215-245.

Chapter
Published: 13 November 2017 in Digital Methods and Remote Sensing in Archaeology
Reads 0
Downloads 0

Digitization of Cultural Heritage assets and sites is a broad term that includes quantitative as well as qualitative data acquisition. Towards a holistic, complete documentation, as outlined by the Venice Charter (1964), capturing the geometry of an object is considered to be one of the first and most essential steps. Within the photogrammetric, the computer vision and the robotics communities, various techniques for 2D, 3D, even 4D data acquisition and digitization have been developed during the past years. Cultural heritage assets are still a challenging object due to the complexity of their shape, the variety of their types, the high requirements of accuracy, and the heterogeneity of the end-users. This chapter focuses on the state of the art of the geometric 3D data acquisition methods, classifying them generally into passive and active. For each category, the available sensors and their working principles are presented and criticized, followed by acquisition network design suggestions and implementation guidelines. In this way, the reader is presented with their merits and disadvantages in order to be able to decide for their correct implementation.

ACS Style

Andreas Georgopoulos; Elisavet Konstantina Stathopoulou. Data Acquisition for 3D Geometric Recording: State of the Art and Recent Innovations. Digital Methods and Remote Sensing in Archaeology 2017, 1 -26.

AMA Style

Andreas Georgopoulos, Elisavet Konstantina Stathopoulou. Data Acquisition for 3D Geometric Recording: State of the Art and Recent Innovations. Digital Methods and Remote Sensing in Archaeology. 2017; ():1-26.

Chicago/Turabian Style

Andreas Georgopoulos; Elisavet Konstantina Stathopoulou. 2017. "Data Acquisition for 3D Geometric Recording: State of the Art and Recent Innovations." Digital Methods and Remote Sensing in Archaeology , no. : 1-26.

Conference paper
Published: 22 February 2017 in Sustainable Transport Development, Innovation and Technology
Reads 0
Downloads 0

Recent advances in contemporary technologies have greatly affected everyday life. In the field of cultural heritage, ICT (Information Communication Technologies) have enabled applications for the thorough multi-dimensional geometric documentation and consequently for the realistic visualization of monuments and artifacts. At the same time the driving force of technology is the game industry. Games and especially Serious Games can be put at the service of cultural heritage, education and tourism exploiting the aforementioned advances and especially the textured three dimensional models. They constitute an attractive platform enabling people to get acquainted with the heritage treasures and get motivated to visit the place and admire the treasures live. In this paper this technological merger is explained and three interconnected applications are presented in order to prove the concept through these implementations. They concern the development of Serious Games for an archaeological site, which aim at the trivial or more specialized information dissemination about that site, while familiarizing the prospect visitor with the environment and the monuments of the site offering the possibility of virtually visiting them. Moreover the development of a virtual museum within a game development environment is presented, which provides the possibility to learn about each exhibit, but also it offers the opportunity to the user to closely examine the exhibits through rotating their three dimensional models. All these examples use realistic models produced for documentation purposes, which convey the real impression of the monuments visualized to the user.

ACS Style

Andreas Georgopoulos; Georgia Kontogianni; Christos Koutsaftis; Margarita Skamantzari. Serious Games at the Service of Cultural Heritage and Tourism. Sustainable Transport Development, Innovation and Technology 2017, 41, 3 -17.

AMA Style

Andreas Georgopoulos, Georgia Kontogianni, Christos Koutsaftis, Margarita Skamantzari. Serious Games at the Service of Cultural Heritage and Tourism. Sustainable Transport Development, Innovation and Technology. 2017; 41 ():3-17.

Chicago/Turabian Style

Andreas Georgopoulos; Georgia Kontogianni; Christos Koutsaftis; Margarita Skamantzari. 2017. "Serious Games at the Service of Cultural Heritage and Tourism." Sustainable Transport Development, Innovation and Technology 41, no. : 3-17.