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Dr. Panagiotis Agrafiotis
Lab. of Photogrammetry, Signal Processing & Computer Vision, National Technical University of Athens; 9 Iroon Polytechneiou Str. - 157 80, Zographou, Athens, Greece

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0 Deep Learning
0 Image Analysis
0 Machine Learning
0 Remote Sensing
0 image classification

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Machine Learning
Shallow Water Bathymetry Mapping

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

Perspective article
Published: 05 March 2021 in Frontiers in Marine Science
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Marine animal forests are benthic communities dominated by sessile suspension feeders (such as sponges, corals, and bivalves) able to generate three-dimensional (3D) frameworks with high structural complexity. The biodiversity and functioning of marine animal forests are strictly related to their 3D complexity. The present paper aims at providing new perspectives in underwater optical surveys. Starting from the current gaps in data collection and analysis that critically limit the study and conservation of marine animal forests, we discuss the main technological and methodological needs for the investigation of their 3D structural complexity at different spatial and temporal scales. Despite recent technological advances, it seems that several issues in data acquisition and processing need to be solved, to properly map the different benthic habitats in which marine animal forests are present, their health status and to measure structural complexity. Proper precision and accuracy should be chosen and assured in relation to the biological and ecological processes investigated. Besides, standardized methods and protocols are strictly necessary to meet the FAIR (findability, accessibility, interoperability, and reusability) data principles for the stewardship of habitat mapping and biodiversity, biomass, and growth data.

ACS Style

Paolo Rossi; Massimo Ponti; Sara Righi; Cristina Castagnetti; Roberto Simonini; Francesco Mancini; Panagiotis Agrafiotis; Leonardo Bassani; Fabio Bruno; Carlo Cerrano; Paolo Cignoni; Massimiliano Corsini; Pierre Drap; Marco Dubbini; Joaquim Garrabou; Andrea Gori; Nuno Gracias; Jean-Baptiste Ledoux; Cristina Linares; Torcuato Pulido Mantas; Fabio Menna; Erica Nocerino; Marco Palma; Gaia Pavoni; Alessandro Ridolfi; Sergio Rossi; Dimitrios Skarlatos; Tali Treibitz; Eva Turicchia; Matan Yuval; Alessandro Capra. Needs and Gaps in Optical Underwater Technologies and Methods for the Investigation of Marine Animal Forest 3D-Structural Complexity. Frontiers in Marine Science 2021, 8, 1 .

AMA Style

Paolo Rossi, Massimo Ponti, Sara Righi, Cristina Castagnetti, Roberto Simonini, Francesco Mancini, Panagiotis Agrafiotis, Leonardo Bassani, Fabio Bruno, Carlo Cerrano, Paolo Cignoni, Massimiliano Corsini, Pierre Drap, Marco Dubbini, Joaquim Garrabou, Andrea Gori, Nuno Gracias, Jean-Baptiste Ledoux, Cristina Linares, Torcuato Pulido Mantas, Fabio Menna, Erica Nocerino, Marco Palma, Gaia Pavoni, Alessandro Ridolfi, Sergio Rossi, Dimitrios Skarlatos, Tali Treibitz, Eva Turicchia, Matan Yuval, Alessandro Capra. Needs and Gaps in Optical Underwater Technologies and Methods for the Investigation of Marine Animal Forest 3D-Structural Complexity. Frontiers in Marine Science. 2021; 8 ():1.

Chicago/Turabian Style

Paolo Rossi; Massimo Ponti; Sara Righi; Cristina Castagnetti; Roberto Simonini; Francesco Mancini; Panagiotis Agrafiotis; Leonardo Bassani; Fabio Bruno; Carlo Cerrano; Paolo Cignoni; Massimiliano Corsini; Pierre Drap; Marco Dubbini; Joaquim Garrabou; Andrea Gori; Nuno Gracias; Jean-Baptiste Ledoux; Cristina Linares; Torcuato Pulido Mantas; Fabio Menna; Erica Nocerino; Marco Palma; Gaia Pavoni; Alessandro Ridolfi; Sergio Rossi; Dimitrios Skarlatos; Tali Treibitz; Eva Turicchia; Matan Yuval; Alessandro Capra. 2021. "Needs and Gaps in Optical Underwater Technologies and Methods for the Investigation of Marine Animal Forest 3D-Structural Complexity." Frontiers in Marine Science 8, no. : 1.

Chapter
Published: 08 April 2020 in Movement, Time, Technology, and Art
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Underwater Cultural Heritage (CH) sites are widely spread; from ruins in coastlines up to shipwrecks in deep. The documentation and preservation of this heritage is an obligation of the mankind, dictated also by the international treaties like the Convention on the Protection of the Underwater Cultural Heritage which fosters the use of “non-destructive techniques and survey methods in preference over the recovery of objects”. However, submerged CH lacks in protection and monitoring in regards to the land CH and nowadays recording and documenting, for digital preservation as well as dissemination through VR to wide public, is of most importance. At the same time, it is most difficult to document it, due to inherent restrictions posed by the environment. In order to create high detailed textured 3D models, optical sensors and photogrammetric techniques seems to be the best solution. This chapter discusses critical aspects of all phases of image based underwater 3D reconstruction process, from data acquisition and data preparation using colour restoration and colour enhancement algorithms to Structure from Motion (SfM) and Multi-View Stereo (MVS) techniques to produce an accurate, precise and complete 3D model for a number of applications.

ACS Style

Dimitrios Skarlatos; Panagiotis Agrafiotis. Image-Based Underwater 3D Reconstruction for Cultural Heritage: From Image Collection to 3D. Critical Steps and Considerations. Movement, Time, Technology, and Art 2020, 141 -158.

AMA Style

Dimitrios Skarlatos, Panagiotis Agrafiotis. Image-Based Underwater 3D Reconstruction for Cultural Heritage: From Image Collection to 3D. Critical Steps and Considerations. Movement, Time, Technology, and Art. 2020; ():141-158.

Chicago/Turabian Style

Dimitrios Skarlatos; Panagiotis Agrafiotis. 2020. "Image-Based Underwater 3D Reconstruction for Cultural Heritage: From Image Collection to 3D. Critical Steps and Considerations." Movement, Time, Technology, and Art , no. : 141-158.

Journal article
Published: 18 January 2020 in Remote Sensing
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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
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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.

Journal article
Published: 17 April 2019 in The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences
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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 as well as archaeological mapping and biological research. UAV imagery processed with Structure from Motion (SfM) and Multi View Stereo (MVS) techniques can provide a low-cost alternative to established shallow seabed mapping techniques offering as well the important visual information. 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 paper, in order to overcome the water refraction errors, we employ machine learning tools that are able to learn the systematic underestimation of the estimated depths. In the proposed approach, based on known depth observations from bathymetric LiDAR surveys, an SVR model was developed able to estimate more accurately the real depths of point clouds derived from SfM-MVS procedures. Experimental results over two test sites along with the performed quantitative validation indicated the high potential of the developed approach.

ACS Style

P. Agrafiotis; D. Skarlatos; A. Georgopoulos; K. Karantzalos. SHALLOW WATER BATHYMETRY MAPPING FROM UAV IMAGERY BASED ON MACHINE LEARNING. The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences 2019, XLII-2/W10, 9 -16.

AMA Style

P. Agrafiotis, D. Skarlatos, A. Georgopoulos, K. Karantzalos. SHALLOW WATER BATHYMETRY MAPPING FROM UAV IMAGERY BASED ON MACHINE LEARNING. The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. 2019; XLII-2/W10 ():9-16.

Chicago/Turabian Style

P. Agrafiotis; D. Skarlatos; A. Georgopoulos; K. Karantzalos. 2019. "SHALLOW WATER BATHYMETRY MAPPING FROM UAV IMAGERY BASED ON MACHINE LEARNING." The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2/W10, no. : 9-16.

Journal article
Published: 17 October 2018 in Remote Sensing
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Images obtained in an underwater environment are often affected by colour casting and suffer from poor visibility and lack of contrast. In the literature, there are many enhancement algorithms that improve different aspects of the underwater imagery. Each paper, when presenting a new algorithm or method, usually compares the proposed technique with some alternatives present in the current state of the art. There are no studies on the reliability of benchmarking methods, as the comparisons are based on various subjective and objective metrics. This paper would pave the way towards the definition of an effective methodology for the performance evaluation of the underwater image enhancement techniques. Moreover, this work could orientate the underwater community towards choosing which method can lead to the best results for a given task in different underwater conditions. In particular, we selected five well-known methods from the state of the art and used them to enhance a dataset of images produced in various underwater sites with different conditions of depth, turbidity, and lighting. These enhanced images were evaluated by means of three different approaches: objective metrics often adopted in the related literature, a panel of experts in the underwater field, and an evaluation based on the results of 3D reconstructions.

ACS Style

Marino Mangeruga; Fabio Bruno; Marco Cozza; Panagiotis Agrafiotis; Dimitrios Skarlatos. Guidelines for Underwater Image Enhancement Based on Benchmarking of Different Methods. Remote Sensing 2018, 10, 1652 .

AMA Style

Marino Mangeruga, Fabio Bruno, Marco Cozza, Panagiotis Agrafiotis, Dimitrios Skarlatos. Guidelines for Underwater Image Enhancement Based on Benchmarking of Different Methods. Remote Sensing. 2018; 10 (10):1652.

Chicago/Turabian Style

Marino Mangeruga; Fabio Bruno; Marco Cozza; Panagiotis Agrafiotis; Dimitrios Skarlatos. 2018. "Guidelines for Underwater Image Enhancement Based on Benchmarking of Different Methods." Remote Sensing 10, no. 10: 1652.

Journal article
Published: 02 July 2018 in Journal of Marine Science and Engineering
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Photogrammetry using structure from motion (SfM) techniques has evolved into a powerful tool for a variety of applications. Nevertheless, limits are imposed when two-media photogrammetry is needed, in cases such as submerged archaeological site documentation. Water refraction poses a clear limit on photogrammetric applications, especially when traditional methods and standardized pipelines are followed. This work tries to estimate the error introduced to depth measurements when no refraction correction model is used and proposes an easy to implement methodology in a modern photogrammetric workflow dominated by SfM and multi-view stereo (MVS) techniques. To be easily implemented within current software and workflow, this refraction correction approach is applied at the photo level. Results over two test sites in Cyprus against reference data suggest that despite the assumptions and approximations made the proposed algorithm can reduce the effect of refraction to two times the ground pixel size, regardless of the depth.

ACS Style

Dimitrios Skarlatos; Panagiotis Agrafiotis. A Novel Iterative Water Refraction Correction Algorithm for Use in Structure from Motion Photogrammetric Pipeline. Journal of Marine Science and Engineering 2018, 6, 77 .

AMA Style

Dimitrios Skarlatos, Panagiotis Agrafiotis. A Novel Iterative Water Refraction Correction Algorithm for Use in Structure from Motion Photogrammetric Pipeline. Journal of Marine Science and Engineering. 2018; 6 (3):77.

Chicago/Turabian Style

Dimitrios Skarlatos; Panagiotis Agrafiotis. 2018. "A Novel Iterative Water Refraction Correction Algorithm for Use in Structure from Motion Photogrammetric Pipeline." Journal of Marine Science and Engineering 6, no. 3: 77.

Journal article
Published: 30 May 2018 in The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences
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In this paper, main challenges of underwater photogrammetry in shallow waters are described and analysed. The very short camera to object distance in such cases, as well as buoyancy issues, wave effects and turbidity of the waters are challenges to be resolved. Additionally, the major challenge of all, caustics, is addressed by a new approach for caustics removal (Forbes et al., 2018) which is applied in order to investigate its performance in terms of SfM-MVS and 3D reconstruction results. In the proposed approach the complex problem of removing caustics effects is addressed by classifying and then removing them from the images. We propose and test a novel solution based on two small and easily trainable Convolutional Neural Networks (CNNs). Real ground truth for caustics is not easily available. We show how a small set of synthetic data can be used to train the network and later transfer the learning to real data with robustness to intra-class variation. The proposed solution results in caustic-free images which can be further used for other tasks as may be needed.

ACS Style

P. Agrafiotis; D. Skarlatos; T. Forbes; C. Poullis; M. Skamantzari; A. Georgopoulos. UNDERWATER PHOTOGRAMMETRY IN VERY SHALLOW WATERS: MAIN CHALLENGES AND CAUSTICS EFFECT REMOVAL. The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences 2018, XLII-2, 15 -22.

AMA Style

P. Agrafiotis, D. Skarlatos, T. Forbes, C. Poullis, M. Skamantzari, A. Georgopoulos. UNDERWATER PHOTOGRAMMETRY IN VERY SHALLOW WATERS: MAIN CHALLENGES AND CAUSTICS EFFECT REMOVAL. The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. 2018; XLII-2 ():15-22.

Chicago/Turabian Style

P. Agrafiotis; D. Skarlatos; T. Forbes; C. Poullis; M. Skamantzari; A. Georgopoulos. 2018. "UNDERWATER PHOTOGRAMMETRY IN VERY SHALLOW WATERS: MAIN CHALLENGES AND CAUSTICS EFFECT REMOVAL." The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2, no. : 15-22.

Review article
Published: 21 April 2018 in Journal of Cultural Heritage
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Since remote times, mankind has been bound to water bodies and evidence of human life from the very beginning hides under the water level, off the coasts, under shallow seas or deep oceans, but also inland water bodies of countries all around the world. Recording, documenting and, ultimately, protecting underwater cultural heritage is an obligation of mankind and dictated by international treaties like the Convention on the Protection of the Underwater Cultural Heritage that fosters and encourages the use of “non-destructive techniques and survey methods in preference over the recovery of objects”. 3D digital surveying and mapping techniques represent an invaluable set of effective tools for reconnaissance, documentation, monitoring, but also public diffusion and awareness of underwater cultural heritage (UCH) assets. This paper presents an extensive review over the sensors and the methodologies used in archaeological underwater 3D recording and mapping together with relevant highlights of well renowned projects in 3D recording underwater.

ACS Style

Fabio Menna; Panagiotis Agrafiotis; Andreas Georgopoulos. State of the art and applications in archaeological underwater 3D recording and mapping. Journal of Cultural Heritage 2018, 33, 231 -248.

AMA Style

Fabio Menna, Panagiotis Agrafiotis, Andreas Georgopoulos. State of the art and applications in archaeological underwater 3D recording and mapping. Journal of Cultural Heritage. 2018; 33 ():231-248.

Chicago/Turabian Style

Fabio Menna; Panagiotis Agrafiotis; Andreas Georgopoulos. 2018. "State of the art and applications in archaeological underwater 3D recording and mapping." Journal of Cultural Heritage 33, no. : 231-248.

Journal article
Published: 13 November 2017 in The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences
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In this paper, a developed low-cost system is described, which aims to facilitate 3D documentation fast and reliably by acquiring the necessary data in outdoor environment for the 3D documentation of façades especially in the case of very narrow streets. In particular, it provides a viable solution for buildings up to 8-10m high and streets as narrow as 2m or even less. In cases like that, it is practically impossible or highly time-consuming to acquire images in a conventional way. This practice would lead to a huge number of images and long processing times. The developed system was tested in the narrow streets of a medieval village on the Greek island of Chios. There, in order to by-pass the problem of short taking distances, it was thought to use high definition action cameras together with a 360˚ camera, which are usually provided with very wide-angle lenses and are capable of acquiring images, of high definition, are rather cheap and, most importantly, extremely light. Results suggest that the system can perform fast 3D data acquisition adequate for deliverables of high quality.

ACS Style

S. Kossieris; O. Kourounioti; P. Agrafiotis; A. Georgopoulos. DEVELOPING A LOW-COST SYSTEM FOR 3D DATA ACQUISITION. The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences 2017, XLII-2/W8, 119 -126.

AMA Style

S. Kossieris, O. Kourounioti, P. Agrafiotis, A. Georgopoulos. DEVELOPING A LOW-COST SYSTEM FOR 3D DATA ACQUISITION. The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. 2017; XLII-2/W8 ():119-126.

Chicago/Turabian Style

S. Kossieris; O. Kourounioti; P. Agrafiotis; A. Georgopoulos. 2017. "DEVELOPING A LOW-COST SYSTEM FOR 3D DATA ACQUISITION." The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2/W8, no. : 119-126.

Conference paper
Published: 21 June 2017 in Proceedings of the 10th International Conference on Predictive Models in Software Engineering
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ACS Style

Nikolaos Doulamis; Panagiotis Agrafiotis; George Athanasiou; Angelos Amditis. Human Object Detection using Very Low Resolution Thermal Cameras for Urban Search and Rescue. Proceedings of the 10th International Conference on Predictive Models in Software Engineering 2017, 311 -318.

AMA Style

Nikolaos Doulamis, Panagiotis Agrafiotis, George Athanasiou, Angelos Amditis. Human Object Detection using Very Low Resolution Thermal Cameras for Urban Search and Rescue. Proceedings of the 10th International Conference on Predictive Models in Software Engineering. 2017; ():311-318.

Chicago/Turabian Style

Nikolaos Doulamis; Panagiotis Agrafiotis; George Athanasiou; Angelos Amditis. 2017. "Human Object Detection using Very Low Resolution Thermal Cameras for Urban Search and Rescue." Proceedings of the 10th International Conference on Predictive Models in Software Engineering , no. : 311-318.

Conference paper
Published: 01 June 2017 in OCEANS 2017 - Aberdeen
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The Underwater Cultural Heritage (UCH) represents a vast historical and scientific resource that, often, is not accessible to the general public due the environment and depth where it is located. Digital technologies (Virtual Museums, Virtual Guides and Virtual Reconstruction of Cultural Heritage) provide a unique opportunity for digital accessibility to both scholars and general public, interested in having a better grasp of underwater sites and maritime archaeology. This paper presents the architecture and the first results of the Horizon 2020 i-MARECULTURE (Advanced VR, iMmersive Serious Games and Augmented REality as Tools to Raise Awareness and Access to European Underwater CULTURal heritage) project that aims to develop and integrate digital technologies for supporting the wide public in acquiring knowledge about UCH. A Virtual Reality (VR) system will be developed to allow users to visit the underwater sites through the use of Head Mounted Displays (HMDs) or digital holographic screens. Two serious games will be implemented for supporting the understanding of the ancient Mediterranean seafaring and the underwater archaeological excavations. An Augmented Reality (AR) system based on an underwater tablet will be developed to serve as virtual guide for divers that visit the underwater archaeological sites.

ACS Style

Fabio Bruno; Antonio Lagudi; Gerardo Ritacco; Panagiotis Agrafiotis; Dimitrios Skarlatos; Jan Cejka; Pavel Kouril; Fotis Liarokapis; Oliver Philpin-Briscoe; Charalambos Poullis; Sudhir Mudur; Bart Simon. Development and integration of digital technologies addressed to raise awareness and access to European underwater cultural heritage. An overview of the H2020 i-MARECULTURE project. OCEANS 2017 - Aberdeen 2017, 1 -10.

AMA Style

Fabio Bruno, Antonio Lagudi, Gerardo Ritacco, Panagiotis Agrafiotis, Dimitrios Skarlatos, Jan Cejka, Pavel Kouril, Fotis Liarokapis, Oliver Philpin-Briscoe, Charalambos Poullis, Sudhir Mudur, Bart Simon. Development and integration of digital technologies addressed to raise awareness and access to European underwater cultural heritage. An overview of the H2020 i-MARECULTURE project. OCEANS 2017 - Aberdeen. 2017; ():1-10.

Chicago/Turabian Style

Fabio Bruno; Antonio Lagudi; Gerardo Ritacco; Panagiotis Agrafiotis; Dimitrios Skarlatos; Jan Cejka; Pavel Kouril; Fotis Liarokapis; Oliver Philpin-Briscoe; Charalambos Poullis; Sudhir Mudur; Bart Simon. 2017. "Development and integration of digital technologies addressed to raise awareness and access to European underwater cultural heritage. An overview of the H2020 i-MARECULTURE project." OCEANS 2017 - Aberdeen , no. : 1-10.

Journal article
Published: 16 May 2017 in The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences
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The National Technical University of Athens undertook the compilation of an "Integrated Diagnostic Research Project and Strategic Planning for Materials, Interventions Conservation and Rehabilitation of the Holy Aedicule of the Church of the Holy Sepulchre in Jerusalem". This paper focuses on the work merging the geometric documentation with the characterization of materials, the identification of building phases and the diagnosis of decay and pathology through the use of analytical and non-destructive techniques. Through this integrated approach, i.e. through the documentation and characterization of the building materials, through the diagnosis of decay and pathology, through the accurate geometric documentation of the building and through the non-destructive prospection of its internal structure, it was feasible to identify the construction phases of the Holy Aedicule, identifying the remnants of the preserved earlier constructions and the original monolithic Tomb. This work, thus, demonstrates that the adoption of an interdisciplinary approach for integrated documentation is a powerful tool for a better understanding of monuments, both in terms of its structural integrity, as well as in terms of its state of preservation, both prerequisites for effective rehabilitation.

ACS Style

A. Georgopoulos; E. Lambrou; G. Pantazis; P. Agrafiotis; A. Papadaki; L. Kotoula; K. Lampropoulos; Ekaterini Delegou; Maria Apostolopoulou; M. Alexakis; A. Moropoulou. MERGING GEOMETRIC DOCUMENTATION WITH MATERIALS CHARACTERIZATION AND ANALYSIS OF THE HISTORY OF THE HOLY AEDICULE IN THE CHURCH OF THE HOLY SEPULCHRE IN JERUSALEM. The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences 2017, XLII-5/W1, 487 -494.

AMA Style

A. Georgopoulos, E. Lambrou, G. Pantazis, P. Agrafiotis, A. Papadaki, L. Kotoula, K. Lampropoulos, Ekaterini Delegou, Maria Apostolopoulou, M. Alexakis, A. Moropoulou. MERGING GEOMETRIC DOCUMENTATION WITH MATERIALS CHARACTERIZATION AND ANALYSIS OF THE HISTORY OF THE HOLY AEDICULE IN THE CHURCH OF THE HOLY SEPULCHRE IN JERUSALEM. The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. 2017; XLII-5/W1 ():487-494.

Chicago/Turabian Style

A. Georgopoulos; E. Lambrou; G. Pantazis; P. Agrafiotis; A. Papadaki; L. Kotoula; K. Lampropoulos; Ekaterini Delegou; Maria Apostolopoulou; M. Alexakis; A. Moropoulou. 2017. "MERGING GEOMETRIC DOCUMENTATION WITH MATERIALS CHARACTERIZATION AND ANALYSIS OF THE HISTORY OF THE HOLY AEDICULE IN THE CHURCH OF THE HOLY SEPULCHRE IN JERUSALEM." The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-5/W1, no. : 487-494.

Chapter
Published: 27 April 2017 in Mixed Reality and Gamification for Cultural Heritage
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The Church of the Holy Sepulchre (Church of the Resurrection) is one of the most important historical sites of Christianity. The current Aedicule structure is the result of various construction phases, damages and destructions, reconstructions, and protection interventions, and as such, it serves as an emblematic case study for five-dimensional (5D) modelling. The innovative and interdisciplinary approach adopted for the modelling of the Holy Aedicule of the Church of the Holy Sepulchre utilizes data from the following: (a) architectural documentation: Description of the current form and structure, as well as its evolution through the ages, based on historic documentation; (b) analysis of construction phases: The construction phases were revealed by a ground-penetrating radar (GPR) survey that was implemented within an integrated methodology, which enabled the technique to identify the various interfaces; (c) geometric documentation: Generation of a 3D high-resolution model, through an automated image-based method and through using terrestrial laser scanning; (d) materials documentation: A wide range of analytical and nondestructive techniques have been used in order to characterize the building materials and extract data for fusion in 5D modelling; and (e) 5D modelling: visualization of the historic construction phases of the Holy Aedicule of the Church of the Holy Sepulchre. The integrated modelling which, after the above analysis, includes enhanced information covering all aspects of the Aedicule structure, geometry, and materials and forms the basis for the creation of an innovative tool that induces mixed reality (MR) with the focus on the Aedicule’s structural evolution (time factor—4D) and on its materials (5D).

ACS Style

Antonia Moropoulou; Andreas Georgopoulos; Manolis Korres; Asterios Bakolas; Kyriakos Labropoulos; Panagiotis Agrafiotis; Ekaterini T. Delegou; Petros Moundoulas; Maria Apostolopoulou; Evangelia Lambrou; George Pantazis; Lydia Kotoula; Alexandra Papadaki; Emmanouil Alexakis. Five-Dimensional (5D) Modelling of the Holy Aedicule of the Church of the Holy Sepulchre Through an Innovative and Interdisciplinary Approach. Mixed Reality and Gamification for Cultural Heritage 2017, 47, 247 -270.

AMA Style

Antonia Moropoulou, Andreas Georgopoulos, Manolis Korres, Asterios Bakolas, Kyriakos Labropoulos, Panagiotis Agrafiotis, Ekaterini T. Delegou, Petros Moundoulas, Maria Apostolopoulou, Evangelia Lambrou, George Pantazis, Lydia Kotoula, Alexandra Papadaki, Emmanouil Alexakis. Five-Dimensional (5D) Modelling of the Holy Aedicule of the Church of the Holy Sepulchre Through an Innovative and Interdisciplinary Approach. Mixed Reality and Gamification for Cultural Heritage. 2017; 47 ():247-270.

Chicago/Turabian Style

Antonia Moropoulou; Andreas Georgopoulos; Manolis Korres; Asterios Bakolas; Kyriakos Labropoulos; Panagiotis Agrafiotis; Ekaterini T. Delegou; Petros Moundoulas; Maria Apostolopoulou; Evangelia Lambrou; George Pantazis; Lydia Kotoula; Alexandra Papadaki; Emmanouil Alexakis. 2017. "Five-Dimensional (5D) Modelling of the Holy Aedicule of the Church of the Holy Sepulchre Through an Innovative and Interdisciplinary Approach." Mixed Reality and Gamification for Cultural Heritage 47, no. : 247-270.

Journal article
Published: 23 February 2017 in The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences
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The work presented in this paper investigates the effect of the radiometry of the underwater imagery on automating the 3D reconstruction and the produced orthoimagery. Main aim is to investigate whether pre-processing of the underwater imagery improves the 3D reconstruction using automated SfM - MVS software or not. Since the processing of images either separately or in batch is a time-consuming procedure, it is critical to determine the necessity of implementing colour correction and enhancement before the SfM - MVS procedure or directly to the final orthoimage when the orthoimagery is the deliverable. Two different test sites were used to capture imagery ensuring different environmental conditions, depth and complexity. Three different image correction methods are applied: A very simple automated method using Adobe Photoshop, a developed colour correction algorithm using the CLAHE (Zuiderveld, 1994) method and an implementation of the algorithm described in Bianco et al., (2015). The produced point clouds using the initial and the corrected imagery are then being compared and evaluated.

ACS Style

P. Agrafiotis; G. I. Drakonakis; A. Georgopoulos; D. Skarlatos. THE EFFECT OF UNDERWATER IMAGERY RADIOMETRY ON 3D RECONSTRUCTION AND ORTHOIMAGERY. The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences 2017, XLII-2/W3, 25 -31.

AMA Style

P. Agrafiotis, G. I. Drakonakis, A. Georgopoulos, D. Skarlatos. THE EFFECT OF UNDERWATER IMAGERY RADIOMETRY ON 3D RECONSTRUCTION AND ORTHOIMAGERY. The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. 2017; XLII-2/W3 ():25-31.

Chicago/Turabian Style

P. Agrafiotis; G. I. Drakonakis; A. Georgopoulos; D. Skarlatos. 2017. "THE EFFECT OF UNDERWATER IMAGERY RADIOMETRY ON 3D RECONSTRUCTION AND ORTHOIMAGERY." The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2/W3, no. : 25-31.

Journal article
Published: 23 February 2017 in The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences
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Μodern advances in the field of image-based 3D reconstruction of complex architectures are valuable tools that may offer the researchers great possibilities integrating the use of such procedures in their studies. In the same way that photogrammetry was a well-known useful tool among the cultural heritage community for years, the state of the art reconstruction techniques generate complete and easy to use 3D data, thus enabling engineers, architects and other cultural heritage experts to approach their case studies in an exhaustive and efficient way. The generated data can be a valuable and accurate basis upon which further plans and studies will be drafted. These and other aspects of the use of image-based 3D data for architectural studies are to be presented and analysed in this paper, based on the experience gained from a specific case study, the Plaka Bridge. This historic structure is of particular interest, as it was recently lost due to extreme weather conditions and serves as a strong proof that preventive actions are of utmost importance in order to preserve our common past.

ACS Style

T. Kouimtzoglou; E. K. Stathopoulou; P. Agrafiotis; A. Georgopoulos. IMAGE-BASED 3D RECONSTRUCTION DATA AS AN ANALYSIS AND DOCUMENTATION TOOL FOR ARCHITECTS: THE CASE OF PLAKA BRIDGE IN GREECE. The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences 2017, XLII-2/W3, 391 -397.

AMA Style

T. Kouimtzoglou, E. K. Stathopoulou, P. Agrafiotis, A. Georgopoulos. IMAGE-BASED 3D RECONSTRUCTION DATA AS AN ANALYSIS AND DOCUMENTATION TOOL FOR ARCHITECTS: THE CASE OF PLAKA BRIDGE IN GREECE. The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. 2017; XLII-2/W3 ():391-397.

Chicago/Turabian Style

T. Kouimtzoglou; E. K. Stathopoulou; P. Agrafiotis; A. Georgopoulos. 2017. "IMAGE-BASED 3D RECONSTRUCTION DATA AS AN ANALYSIS AND DOCUMENTATION TOOL FOR ARCHITECTS: THE CASE OF PLAKA BRIDGE IN GREECE." The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2/W3, no. : 391-397.

Journal article
Published: 23 February 2017 in ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences
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This paper investigates immersive technologies to increase exploration time in an underwater archaeological site, both for the public, as well as, for researchers and scholars. Focus is on the Mazotos shipwreck site in Cyprus, which is located 44 meters underwater. The aim of this work is two-fold: (a) realistic modelling and mapping of the site and (b) an immersive virtual reality visit. For 3D modelling and mapping optical data were used. The underwater exploration is composed of a variety of sea elements including: plants, fish, stones, and artefacts, which are randomly positioned. Users can experience an immersive virtual underwater visit in Mazotos shipwreck site and get some information about the shipwreck and its contents for raising their archaeological knowledge and cultural awareness.

ACS Style

F. Liarokapis; P. Kouřil; P. Agrafiotis; S. Demesticha; J. Chmelík; D. Skarlatos. 3D MODELLING AND MAPPING FOR VIRTUAL EXPLORATION OF UNDERWATER ARCHAEOLOGY ASSETS. ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences 2017, XLII-2/W3, 425 -431.

AMA Style

F. Liarokapis, P. Kouřil, P. Agrafiotis, S. Demesticha, J. Chmelík, D. Skarlatos. 3D MODELLING AND MAPPING FOR VIRTUAL EXPLORATION OF UNDERWATER ARCHAEOLOGY ASSETS. ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. 2017; XLII-2/W3 ():425-431.

Chicago/Turabian Style

F. Liarokapis; P. Kouřil; P. Agrafiotis; S. Demesticha; J. Chmelík; D. Skarlatos. 2017. "3D MODELLING AND MAPPING FOR VIRTUAL EXPLORATION OF UNDERWATER ARCHAEOLOGY ASSETS." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2/W3, no. : 425-431.

Journal article
Published: 23 February 2017 in The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences
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An interdisciplinary team from the National Technical University of Athens is performing the restoration of the Holy Aedicule, which covers the Tomb of Christ within the Church of the Holy Sepulchre in Jerusalem. The first important task was to geometrically document the monument for the production of the necessary base material on which the structural and material prospection studies would be based. One task of this action was to assess the structural behavior of this edifice in order to support subsequent works. It was imperative that the internal composition of the construction be documented as reliably as possible. To this end several data acquisition techniques were employed, among them ground penetrating radar. Interpretation of these measurements revealed the position of the rock, remnants of the initial cave of the burial of Christ. This paper reports on the methodology employed to construct the 3D model of the rock and introduce it into the 3D model of the whole building, thus enhancing the information about the structure. The conversion of the radargrams to horizontal sections of the rock is explained and the construction of the 3D model and its insertion into the 3D model of the Holy Aedicule is described.

ACS Style

P. Agrafiotis; K. Lampropoulos; A. Georgopoulos; A. Moropoulou. 3D MODELLING THE INVISIBLE USING GROUND PENETRATING RADAR. The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences 2017, XLII-2/W3, 33 -37.

AMA Style

P. Agrafiotis, K. Lampropoulos, A. Georgopoulos, A. Moropoulou. 3D MODELLING THE INVISIBLE USING GROUND PENETRATING RADAR. The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. 2017; XLII-2/W3 ():33-37.

Chicago/Turabian Style

P. Agrafiotis; K. Lampropoulos; A. Georgopoulos; A. Moropoulou. 2017. "3D MODELLING THE INVISIBLE USING GROUND PENETRATING RADAR." The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2/W3, no. : 33-37.

Conference paper
Published: 31 October 2016 in Transactions on Petri Nets and Other Models of Concurrency XV
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The project iMARECULTURE is focusing in raising European identity awareness using maritime and underwater cultural interaction and exchange in Mediterranean Sea. Commercial ship routes joining Europe with other cultures are vivid examples of cultural interaction, while shipwrecks and submerged sites, unreachable to wide public are excellent samples that can benefit from immersive technologies, augmented and virtual reality. The projects aim to bring inherently unreachable underwater cultural heritage within digital reach of the wide public using virtual visits and immersive technologies. Apart from reusing existing 3D data of underwater shipwrecks and sites, with respect to ethics, rights and licensing, to provide a personalized dry visit to a museum visitor or augmented reality to the diver, it also emphasizes on developing pre- and after- encounter of the digital or physical museum visitor. The former one is implemented exploiting geospatial enabled technologies for developing a serious game of sailing over ancient Mediterranean and the latter for an underwater shipwreck excavation game. Both games are realized thought social media, in order to facilitate information exchange among users. The project supports dry visits providing immersive experience through VR Cave and 3D info kiosks on museums or through the web. Additionally, aims to significantly enhance the experience of the diver, visitor or scholar, using underwater augmented reality in a tablet and an underwater housing. The consortium is composed by universities and SMEs with experience in diverse underwater projects, existing digital libraries, and people many of which are divers themselves.

ACS Style

D. Skarlatos; P. Agrafiotis; T. Balogh; F. Bruno; Filipe Castro; Barbara Davidde Petriaggi; Stella Demesticha; A. Doulamis; Pierre Drap; A. Georgopoulos; F. Kikillos; P. Kyriakidis; Fotis Liarokapis; Charalambos Poullis; Selma Rizvic. Project iMARECULTURE: Advanced VR, iMmersive Serious Games and Augmented REality as Tools to Raise Awareness and Access to European Underwater CULTURal heritagE. Transactions on Petri Nets and Other Models of Concurrency XV 2016, 805 -813.

AMA Style

D. Skarlatos, P. Agrafiotis, T. Balogh, F. Bruno, Filipe Castro, Barbara Davidde Petriaggi, Stella Demesticha, A. Doulamis, Pierre Drap, A. Georgopoulos, F. Kikillos, P. Kyriakidis, Fotis Liarokapis, Charalambos Poullis, Selma Rizvic. Project iMARECULTURE: Advanced VR, iMmersive Serious Games and Augmented REality as Tools to Raise Awareness and Access to European Underwater CULTURal heritagE. Transactions on Petri Nets and Other Models of Concurrency XV. 2016; ():805-813.

Chicago/Turabian Style

D. Skarlatos; P. Agrafiotis; T. Balogh; F. Bruno; Filipe Castro; Barbara Davidde Petriaggi; Stella Demesticha; A. Doulamis; Pierre Drap; A. Georgopoulos; F. Kikillos; P. Kyriakidis; Fotis Liarokapis; Charalambos Poullis; Selma Rizvic. 2016. "Project iMARECULTURE: Advanced VR, iMmersive Serious Games and Augmented REality as Tools to Raise Awareness and Access to European Underwater CULTURal heritagE." Transactions on Petri Nets and Other Models of Concurrency XV , no. : 805-813.