This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Zenodo (CERN European Organization for Nuclear Research), May 31, 2023
This work presents the role of 3D visualization and analysis of monuments and archaeological site... more This work presents the role of 3D visualization and analysis of monuments and archaeological sites in producing useful data regarding their preservation condition.The progress made in 3D digitization technologies, in combination with finding new data processing algorithms, have enabled reliable and highly detailed digitization of the characteristics of different parts of the monuments. Due to both the effects of nature and human intervention, monuments and sites all over the world have changed over time. The use of analog documentation data can help significantly towards this direction. In this work, we use as case study a luxurious residential complex in the Athenian Agora, known as Omega house. We use a retrospective 3D model, created with photographs taken in the late 60's and early 70's, in comparison with a 3D model made with contemporary digital photos, taken in 2017. All models are georeferenced. The old model is produced using analog terrestrial photographs and aerial photos taken by a blimp. The new one is created by terrestrial digital photographs in combination with images taken by unmanned aerial vehicle commonly known as a drone. The 3D models have been divided into smaller parts so that we can analyze them with greater accuracy separately, and then the whole models were compared between them too. The Constructive Solid Geometry (CSG) modeling scheme is used and Boolean operations are applied to find the difference and intersection of the models.The comparison that is carried out in the current work elaborates on legacy data usefulness and utility for monitoring the Omega House condition. The type of investigation proposed in this work proves that legacy data can be repurposed and attain a new role through change detection techniques.
ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Jun 17, 2021
In this work the problem of change detection in high-resolution (HR) satellite images is addresse... more In this work the problem of change detection in high-resolution (HR) satellite images is addressed. The active learning (AL) algorithm Bayesian active learning disagreement (BALD) is applied on WorldView images of urban and suburban areas in the island of Crete, Greece. Comparisons with results from random sampling (RS) on AL are carried out. Several cases of selecting different amounts of images in the training set of a convolutional neural network (CNN) are experimented. The results show that the validation accuracy of classification as changed or unchanged of the BALD algorithm is superior to that of the RS algorithm. Indeed, the BALD algorithm achieves zero test error against the test errors 34.6% and 38.5% of the RS algorithm. Actually, as the amount of training images increases, the accuracy also increases. Interesting experiments could be executed in the future utilizing estimators from robust statistics inside the AL acquisition function framework. Up to now in the literature no other work has appeared to present deep AL on WorldView images for change detection.
ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Jun 7, 2016
Nowadays coastline extraction and tracking of its changes become of high importance because of th... more Nowadays coastline extraction and tracking of its changes become of high importance because of the climate change, global warming and rapid growth of human population. Coastal areas play a significant role for the economy of the entire region. In this paper we propose a new methodology for automatic extraction of the coastline using aerial images. A combination of a four step algorithm is used to extract the coastline in a robust and generalizable way. First, noise distortion is reduced in order to ameliorate the input data for the next processing steps. Then, the image is segmented into two regions, land and sea, through the application of a local threshold to create the binary image. The result is further processed by morphological operators with the aim that small objects are being eliminated and only the objects of interest are preserved. Finally, we perform edge detection and active contours fitting in order to extract and model the coastline. These algorithmic steps are illustrated through examples, which demonstrate the efficacy of the proposed methodology.
ISPRS international journal of geo-information, Apr 17, 2018
3D building façade reconstruction has become a very popular topic in various applications related... more 3D building façade reconstruction has become a very popular topic in various applications related to restoration and preservation of architectural structures as well as urban planning. This paper deals with the reconstruction of realistic 3D models of buildings façades, in the urban environment for cultural heritage. We present an approach that enables the relation of stereoscopic images with tacheometry data. The proposed multimodal fusing scheme results in an accurate 3D realistic façade reconstruction and provides a fast and low cost solution. In the first stage of the proposed approach a 2D skeleton of the building is extracted from the viewed scene using Active Contour and Hough line extraction. The next stage of our method utilizes depth information, extracted from a stereoscopic layout, to infer the structural details of inner façade structures, such as windows or doors. In the final stage, the structural information extracted from the image data is integrated with georeferenced point datasets. The final output of our method is a georeferenced 3D model of the structure's façade, which can be further refined with the use of image-driven texture information.
Taking into consideration that growth of urban population has impacts on land use and that managi... more Taking into consideration that growth of urban population has impacts on land use and that managing urban population change is one of the most important contemporary challenges, this paper deals with the sustainable development of peri-urban zones which represent important an environment where employment opportunities are developed and resources exploited (particularly agricultural resources) and environment where important recreational and leisure activities could be pursued. Within the review of current concepts and planning practices, the concepts of multifunctional agriculture and multifunctional landscapes in peri-urban zones are pointed out, as well as EU Developing Periurban Projects. The paper particularly focuses on the current situation in Serbia, where there is no specific legal basis for the planning of peri-urban areas, although there are positive examples of strategies, regulations and planning documents which treat agriculture and greenery in peri-urban zones in a sus...
Current Multi-View Stereo (MVS) algorithms are tools for high-quality 3D model reconstruction, st... more Current Multi-View Stereo (MVS) algorithms are tools for high-quality 3D model reconstruction, strongly depending on image spatial resolution. In this context, the combination of image Super-Resolution (SR) with image-based 3D reconstruction is turning into an interesting research topic in photogrammetry, around which however only a few works have been reported so far in the literature. Here, a thorough study is carried out on various state-of-the-art image SR techniques to evaluate the suitability of such an approach in terms of its inclusion in the 3D reconstruction process. Deep-learning techniques are tested here on a UAV image dataset, while the MVS task is then performed via the Agisoft Metashape photogrammetric tool. The data under experimentation are oblique cultural heritage imagery. According to results, point clouds from low-resolution images present quality inferior to those from upsampled high-resolution ones. The SR techniques HAT and DRLN outperform bicubic interpolat...
Archaeological monuments all over the world face problems of conservation and maintenance due to ... more Archaeological monuments all over the world face problems of conservation and maintenance due to natural events and processes as well as human intervention, all of which lead to their alteration and deterioration. In particular, monuments and sites that have been excavated and left exposed to the elements experience decay, which would have taken centuries prior to excavation, in just a few years when left unprotected. Thus, the necessity to detect and observe changes over time becomes paramount. Legacy data and, in particular, retrospective photogrammetric modeling, are vital tools in this process. In this work we compare two photogrammetric 3D models of the Omega House, in the Athenian Agora, to assess how much the site has changed between the time of its first excavation in 1972 and its current state. Constructive Solid Geometry (CSG) is utilized to perform Boolean operations. Additionally, distance and volume calculations are performed. The software CloudCompare was used for this...
Monitoring the changes of the coastal areas using remote sensing data and geographic information systems
Seventh International Conference on Remote Sensing and Geoinformation of the Environment (RSCy2019)
In this paper we monitor the changes of the shoreline and coastal area using satellite data. The ... more In this paper we monitor the changes of the shoreline and coastal area using satellite data. The case study is at the area of Georgioupoli which is a mainly tourism area located on the Northern part of the island of Crete. In our study, high resolution Quickbird and WorldView-3 satellite sensor images were analyzed with a resolution of 0.60m and 0.30m respectively, at a time period of 13 years. The premise is that interpretation of remote sensing imagery can provide useful and interesting information. Combination of remote sensing techniques and geospatial analysis was applied in order to visualize and identify land cover changes. This integrated approach, was successfully implemented for the assessment of natural resources, where two images on different dates were compared, in order to quantify the type and amount of changes that have been occurred in the coastal area. Currently, various applications of change detection have been applied in many sectors such as, agriculture, hydrology, forestry and environment. For this purpose, the shoreline was depicted numerically and manually for each year. In addition, NDVI classification was applied to quantify land cover changes near the coastal area. Shoreline measurements provide information about the coastal loss over the years and the changes of the coastal area. The high resolution satellite images allow the detection of erosion and accretion of the last years. Based on the results, we showed that surfaces of the coastal area and close to it were reduced or totally disappeared. Finally, significant changes were also detected in the vegetation for a 13-year period. These changes should be taken under consideration for the long term sustainable development and economic growth of the coastal area.
— Capturing Multimedia Events such as natural disas-ters, accident reports, building damage repor... more — Capturing Multimedia Events such as natural disas-ters, accident reports, building damage reports, political events, etc., are expensive functionalities due to the number and training of the people required, as well as the time involved in the captur-ing and post-processing of multimedia. In addition, the captured multimedia content often fails to give the viewer a comprehensive understanding of the event captured in context. We present a model and a mobile system for multimedia event capturing by a one-man-crew. The system supports: (a) the real time capturing of complex multimedia events of different types; (b) the recording of the capturing process and the metadata associated with the events; (c) the visualization of the events and the capturing process; and (d) the learning and preparation of the one-man-crew that will do the multimedia event capturing. I.
Data Acquisition and Mapping for Geohazard Analysis
Communications in Computer and Information Science, 2018
The aim of the current work is to introduce bathymetry data into Geographic Information Systems t... more The aim of the current work is to introduce bathymetry data into Geographic Information Systems tools for mapping, monitoring and assessing the geohazards in the Greek islands between Crete and Kasos at the Mediterranean sea. The offshore area lying east of Crete is studied on the basis of new bathymetric data. The data was obtained by a multibeam sonar system which allows the imaging of the seafloor. The collected multibeam data have been extensively processed in order to be cleaned of erroneous beams, filtered of noise, processed of navigation data and interpolated of missing beams. The analysis and representation was performed with the ArcGIS software. Resulting maps were analyzed and presented. The analysis of the slope values and the watershed at the eastern part of Crete reflects intense tectonic activity. We have found out that the basin geometry is an elongated rectangular which is divided into seven sub-basins. The multibeam bathymetric data show that the relief is a comple...
Proceedings of the 4th International Conference on Geographical Information Systems Theory, Applications and Management, 2018
The purpose of this research is the identification, recording, mapping and photographic imaging o... more The purpose of this research is the identification, recording, mapping and photographic imaging of the special volcanic geoforms as well as the cultural monuments of the volcanic Methana Peninsula. With the use of novel methods the aim is to reveal and study the impressive topographic features of the Methana geotope and discover its unique geodiversity. The proposed hiking trails along with the Methana's archaeology and history, will be highlighted through the creation of an 'intelligent' interactive map (Story Map). Two field trips have been conducted for the collection of further information and the digital mapping of the younger volcanic flows of Kammeni Chora with drones. Through the compiled data, thematic maps were created depicting the lava flows and the most important points of the individual hiking paths. The thematic maps were created using a Geographic Information System (GIS). Finally, those maps were the basis for the creation of the main Story Map. The decision to use Story Maps was based on the numerous advantages on offer such as user-friendly mapping, ease of use and interaction and user customized displays.
This paper puts forward a 3D reconstruction methodology applied to the restoration of historic bu... more This paper puts forward a 3D reconstruction methodology applied to the restoration of historic buildings taking advantage of the speed, range and accuracy of a total geodetic station. The measurements representing geo-referenced points produced an interactive and photorealistic geometric mesh of a monument named 'Neoria.' 'Neoria' is a Venetian building located by the old harbor at Chania, Crete, Greece. The integration of tacheometry acquisition and computer graphics puts forward a novel integrated software framework for the accurate 3D reconstruction of a historical building. The main technical challenge of this work was the production of a precise 3D mesh based on a sufficient number of tacheometry measurements acquired fast and at low cost, employing a combination of surface reconstruction and processing methods. A fully interactive application based on game engine technologies was developed. The user can visualize and walk through the monument and the area around it as well as photorealistically view it at different times of day and night. Advanced interactive functionalities are offered to the user in relation to identifying restoration areas and visualizing the outcome of such works. The user could visualize the coordinates of the points measured, calculate distances and navigate through the complete 3D mesh of the monument. The geographical data are stored in a database connected with the application. Features referencing and associating
Reduction of building façade model complexity using computer vision
2016 IEEE International Conference on Imaging Systems and Techniques (IST), 2016
3D Building façade reconstruction enables the implementation of delicate actions related to resto... more 3D Building façade reconstruction enables the implementation of delicate actions related to restoration, support and presentation of architectural structures. In particular, model complexity can be significantly reduced through the incorporation of computer vision and image processing tools, aiming towards the estimation of structural 3D feature characteristics instead of their actual GPS specification. In this paper we present a strategy for constructing reduced-complexity 3D models, which combines stereo vision images and morphological processing methods. Initially, the building skeleton is extracted and modeled with the use of Hough transformation and Active Contours. Subsequently, the building's façade depth map is derived using the stereo camera layout, for the refinement of inner skeleton details, such as the protrusion of windows or doors. These image-driven features are fused with Georeferenced data in order to complete the full building's skeleton model. The proposed reconstruction framework is tested on the site of Neoria buildings, a historical (Venetian) site in Chania, Crete, Greece.
Spatial data are used for location based services and to support traffic management systems. Data... more Spatial data are used for location based services and to support traffic management systems. Data are gathered, saved and managed in a central database where, in principal, every user can access them putting data in a temporary database and then integrate them to a central. The proposed system uses a connection between database and trust engines in order to provide transparency. Security is an important aspect in our system to give confidence to the users to use their online services. We present an architecture for the implementation. The implemented system has been used in a small scenario for traffic information in a city center.
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