Lemonia Ragia

Contextual Geospatial Picture Understanding, Management and Visualization

We describe SPIM (Spatial Image Management), a framework and a system that allow identification and visualization of the semantics of distant objects in nature, which exist in pictures taken by mobile devices. Semantic objects in nature are represented on 3D maps and tagged with semantic and spatial descriptors. The system functionality creates, on top of pictures, a layer that allows semantic user browsing in augmented geospatial images, semantic object identification in pictures, object interaction, contextual map visualization, and interlinking of information in digital libraries and the web. We present requirements of semantic geospatial descriptions, system functionality, matching algorithms and experimental results.

Outdoors Mobile Augmented Reality Application Visualizing 3D Reconstructed Historical Monuments.

We present a mobile Augmented Reality (AR) tourist guide to be utilized while walking around cultural heritage sites located in the Old town of the city of Chania, Crete, Greece. Instead of the traditional static images or text presented by mobile, location-aware tourist guides, the main focus is to seamlessly and transparently superimpose geo-located 3D reconstructions of historical buildings, in their past state, onto the real world, while users hold their consumer grade mobile phones walking on-site, without markers placed onto the buildings, offering a Mobile Augmented Reality experience. we feature three monuments; e.g., the ‘GialiTzamisi’, an Ottoman mosque; part of the south side of a Byzantine Wall and the ‘Saint Rocco’ Venetian chapel. Advances in mobile technology have brought AR to the public by utilizing the camera, GPS and inertial sensors present in modern smart phones. Technical challenges such as accurate registration of 3D and real world, in outdoors settings, have prevented AR becoming main stream. We tested commercial AR frameworks and built a mobile AR app which offers users, while visiting these monuments in the challenging outdoors environment, a virtual reconstruction displaying the monument in its past state superimposed onto the real world. Position tracking is based on the mobile phone’s GPS and inertial sensors. The users explore interest areas and unlock historical information, earning points. By combining AR technologies with locationaware, gamified and social aspects, we enhance interaction with cultural heritage sites.

An interactive story map for the Methana volcanic peninsula

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.

Precise photorealistic visualization for restoration of historic buildings based on tacheometry data

Abstract 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 the database with the monument are developed. The goal was to utilize a small number of acquired data points and present a fully interactive visualization of a geo-referenced 3D model.

Fusing Georeferenced and Stereoscopic Image Data for 3D Building Façade Reconstruction

3D building facade 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 facades, 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 facade 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 facade 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 facade, which can be further refined with the use of image-driven texture information.

Morphotectonic Analysis between Crete and Kasos.

The morphotectonic structure of the offshore area lying between Crete and Kasos is studied on the basis of new detailed bathymetric data. The resulting bathymetric map is presented. Qualitative analysis of morphological slope values, as well as the analysis of the watershed at the eastern part of Crete, confirms that the current seabed topographic relief reflects intense tectonic activity. The high morphological slope values indicate well-defined morphotectonic features, which mainly trend SW-NE and, secondarily, SSW-NNE. The main large-scale tectonic structures trend SW-NE correspond to the marginal faults that bound the CreteKasos basin. The overall basin geometry is an elongated rectangular which is divided into seven sub-basins, and the deepest one (2800m) is located at the eastern part of the area. Moreover, the complex regime of the seafloor includes submarine canyons, landslides and a well-defined slump with vertical displacement more

Reduction of building façade model complexity using computer vision

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 buildings 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 buildings skeleton model. The proposed reconstruction framework is tested on the site of Neoria buildings, a historical (Venetian) site in Chania, Crete, Greece.

3D Building Reconstruction using Stereo Camera and Edge Detection

Three dimensional geo-referenced data for buildings are very important for many applications like cadastre, urban and regional planning, environmental issues, archaeology, architecture, tourism and energy. The acquisition and update of existing databases is time consuming and involves specialized equipment and heavy post processing of the raw data. In this study we propose a system for urban area data based on stereo cameras for the reconstruction of the 3D space and subsequent matching with limited geodetic measurements. The proposed stereo system along with image processing algorithms for edge detection and characteristic point matching in the two cameras allows for the reconstruction of the 3D scene in camera coordinates. The matching with the available geodetic data allows for the mapping of the entire scene on the word coordinates and the reconstruction of real world distance and angle measurements.

Automated Waterline Extraction for Optimal Land Use - A Case Study in Crete

Coastal areas in Greece play an important role to the economic growth of the country. Especially in the islands as a major tourist destination, new tourist infrastructure is continuously being built. To optimize land use and protect current infrastructure, we need to properly define the waterline. In addition, the waterline is changing dynamically due to climate change and weather conditions, so it has to be monitored. The proposed framework is focused on the automatic extraction of waterline from aerial images using advanced image processing techniques. We plan to integrate the Greek cadastral data in the framework and along with spatial data analysis to be able to proceed with both coastal and cadastral data. Additional functionalities are provided to the planners, through metrics for distance and surface area calculations, in order to extract useful information for sustainable region planning of the coastal area. The results can be visualized in the images with the metrics

A digital library system for semantic spatial information extraction from images

Spatial information delivery is of high importance today for mobile applications. Knowledge about spatial objects includes not only location of the user, direction and time, but also knowledge of the semantics of the spatial objects. These semantics can be related to the user profile and users interests at the time, which can be expressed using domain specific ontologies, such as cultural ontologies, nature ontologies, tourism ontologies and others. The system then should screen this information and deliver it to the mobile user device. The system uses as input digital images taken from a simple, modern digital camera. In this paper we present a digital library system for image storage, image handling and extraction of spatial information based on the semantics spatial information that the system manages.