Charalampos Georgiadis

Access-rule certificates for secure distributed healthcare applications over the Internet

Access control in medical information systems distributed over the Internet is an important issue directly related to the protection of patients’ privacy. It is therefore essential to satisfy the increasing demand for exploiting Internet mechanisms in order to achieve a secure health information network. This can only be done, however, if it can be guaranteed that appropriate measures have been taken to preserve a satisfactory level of security for the information concerned. Recent efforts in this direction rely on public-key cryptography and digital certificates. Identity certificates are suitable for identification and authentication purposes. In addition, attribute certificates are another type of certificate particularly suitable for authorization purposes. In order to fully exploit digital certificates to protect distributed healthcare applications over the Internet, we propose the use of a third type of certificate, called access-rule certificates, which are useful for the enforcement of global access-control mechanisms between different organizations. In this paper, we present the structure of those three types of certificate, as well as the access-control procedures when using them; we describe the architecture of the proposed system whose purpose is to explore the use of certificates for the implementation of a suitable security policy for healthcare environments.

A flexible authorization mechanism for virtual organizations

Authorization decisions are a critical security concern in todays distributed large information systems. These authorizations are significantly different from those in centralized or smaller systems. Mobile agent technology on the other hand provides a useful tool to explore and facilitate information sharing in distributed systems. However, agents are often restricted by the security problems related to the large scale distributed systems and the multi-user operating system environments within they usually operate. This article provides a suitable framework for authorizing mobile agents where an outsized and dynamic set of principals forming a virtual organization (VO), with mutual mistrust between them, has to rely on pieces of application code which autonomously migrate and execute on consecutive hosts. The role based access control model (RBAC) is used for dynamically assigning security roles to visiting agents on each hosting platform. The proposed methodology is particularly suitable for handling authorizations in VOs.

Programming a view-based active access-control system for healthcare environments

Modern healthcare information systems need active security mechanisms that are capable of controlling access to medical data, according to the current need-to-know requirements of users. An access-control model that fits the above requirements is the already known C-TMAC (Context-based Team Access Control) model, which incorporates active security features and provides tight and just-in-time management of user permissions. In this paper, an implementation approach of an access control system that is based on the C-TMAC model is proposed. To further enforce fine-grained access control, we adopt view-based protection that permits the use of flexible granularities to define the objects to be protected. For this purpose, a simple case in a healthcare environment is assumed and a detailed description of setting up the corresponding access rules in a view-based fashion is presented. An implementation paradigm of the access control process that takes place on the presence of a user request is demonstrated.

Evaluating horizontal positional accuracy of low-cost UAV orthomosaics over forest terrain using ground control points extracted from different sources

Within the field of forestry, forest road mapping and inventory plays an important role in management activities related to wood harvesting industry, sentiment and water run-off modelling, biodiversity distribution and ecological connectivity, recreation activities, future planning of forest road networks and wildfire protection and fire-fighting. Especially in countries of the Mediterranean Rim, knowledge at regional and national scales regarding the distribution and the characteristics of rural and forest road network is essential in order to ensure an effective emergency management and rapid response of the fire-fighting mechanism. Yet, the absence of accurate and updated geodatabases and the drawbacks related to the use of traditional cartographic methods arising from the forest environment settings, and the cost and efforts needed, as thousands of meters need to be surveyed per site, trigger the need for new data sources and innovative mapping approaches. Monitoring the condition of unpaved forest roads with unmanned aerial vehicle technology is an attractive option for substituting objective, laboursome surveys. Although photogrammetric processing of UAV imagery can achieve accuracy of 1-2 centimeters and dense point clouds, the process is commonly based on the establishment of control points. In the case of forest road networks, which are linear features, there is a need for a great number of control points. Our aim is to evaluate low-cost UAV orthoimages generated over forest areas with GCP’s captured from existing national scale aerial orthoimagery, satellite imagery available through a web mapping service (WMS), field surveys using Mobile Mapping System and GNSS receiver. We also explored the direct georeferencing potential through the GNSS onboard the low cost UAV. The results suggest that the GNSS approach proved to most accurate, while the positional accuracy derived using the WMS and the aerial orthoimagery datasets deemed satisfactory for the specific task at hand. The direct georeferencing procedure seems to be insufficient unless an onboard GNSS with improved specifications or Real-Time Kinematic (RTK) capabilities is used.

Coastal 3D mapping using very high resolution satellite images and UAV imagery: new insights from the SAVEMEDCOASTS project

Global climate changes are a main factor of risk for infrastructures and people living along the coasts around the world. In this context, sea level rise, coastal retreat and storm surges pose serious threats to coastal zones. In order to assess the expected coastal changes for the next decades, a detailed knowledge of the site’s topography (coastline position, DTM, bathymetry) is needed. This paper focuses on the use of very high resolution satellite data and UAV imagery for the generation of accurate very-high and ultra-high mapping of coastal areas. In addition, the use of very high resolution multi-spectral satellite data is investigated for the generation of coastal bathymetry maps. The paper presents a study for the island of Lipari and the coasts of Cinque Terre (Italy) and the island of Lefkas (Greece). For Lefkas, two areas of the island were mapped (the city of Lefkas and its adjoining lagoon in the north side of the island, and the Bay of Vasiliki at the south part of the island) using World View 1, and Wolrd View 3 satellite images, and UAV imagery. The satellite processing provided results that demonstrated an accuracy of approximately 0.25 m plannimetrically and 0.70 m vertically. The processing of the UAV imagery resulted in the generation of DTMs and orthophotos with an accuracy of approximately 0.03-0.04 meters. In addition, for the Vasiliki bay in the south of the island the World View 3 imagery was used for the estimation of a bathymetry map of the bay. The achieved results yielded an accuracy of 0.4 m. For the sites of Lipari and Cinque Terre (both in Italy), UAV surveys allowed to extract a DTM at about 2 cm of pixel resolution. The integration of topographic data with high resolution multibeam bathymetry and expected sea level rise from IPCC AR5 2.6 and 8.5 climatic scenarios, will be used to map sea level rise scenarios for 2050 and 2100, taking into account the Vertical Land Motion (VLM) as estimated from CGPS data. The above-mentioned study was realized during the implementation of the SAVEMEDCOASTS project (Sea level rise scenarios along the Mediterranean coasts, funded by the European Commission ECHO A.5, GA ECHO/SUB/2016/742473/PREV16, www.savemedcoasts.eu).

Assessment of Radiometric Resolution Impact on Remote Sensing Data Classification Accuracy

Improved sensor characteristics are generally assumed to increase the potential accuracy of image classification and information extraction from remote sensing imagery. However, the increase in data volume caused by these improvements raise challenges associated with the selection, storage, and processing of this data, and with the cost-effective and timely analysis of the remote sensing datasets. Previous research has extensively assessed the relevance and impact of spatial, spectral and temporal resolution of satellite data on classification accuracy, but little attention has been given to the impact of radiometric resolution. This study focuses on the role of radiometric resolution on classification accuracy of remote sensing data through different classification experiments over three different sites. The experiments were carried out using fine and low scale radiometric resolution images classified through a bagging classification tree. The classification experiments addressed different aspects of the classification road map, including among others, binary and multiclass classification schemes, spectrally and spatially enhanced images, as well as pixel and objects as units of the classification. In addition, the impact of image radiometric resolution on computational time and the information content in fineand low-resolution images was also explored. While in certain cases, higher radiometric resolution has led to up to 8% higher classification accuracies compared to lower resolution radiometric data, other results indicate that higher radiometric resolution does not necessarily imply improved classification accuracy. Also, classification accuracy of spectral indices and texture bands is not related so much to the radiometric resolution of the original remote sensing images but rather to their own radiometric resolution. Overall, the results of this study suggest that data selection and classification need not always adhere to the highest possible radiometric resolution.

Unmanned Aerial Vehicles and the Multi Temporal Mapping Results of the Dispilio Lakeside Prehistoric Settlement

In this paper the authors present the evolution of the Unmanned Aerial Vehicles (UAV) and photogrammetric processing software technology through the multi temporal mapping of the lakeside Palaeolithic settlement of Dispilio (Kastoria, Greece). The study of the settlement initiated in 2006 using a Remote Control (RC) Helicopter, which was not equipped with an automated navigation and image acquisition system. Currently a multi-copter drone is used that can demonstrate flight stability, is capable of hovering in small heights and is equipped with an automated navigation and image acquisition system. With respect to the photogrammetric processing software at the start of the study specialized single image processing software like Bentley IRAS/c® were used for the production of rectified images, followed by the use of stereo image processing software like LPS® (Erdas) that have the ability to produce B/W Digital Terrain Models (DTM) and ortho rectified images. Currently specialized multi photo processing software is used like Agisoft Photoscan® or Imagine UAV® (Erdas) that the ability to produce dense coloured point clouds and ortho rectified images.

Aerial and Remote Sensing Archaeology

New techniques and methodological procedures, which would allow at a short time and at low cost for the identification of a new archaeological sites, were always in the interest of archaeologists. In addition, fast and accurate 3D modelling and documentation techniques were also always a hot research topic because they can help archeologists to document active excavation sites fast, thus helping them to advance the excavation in a timely manner. In this chapter, aerial and remote sensing archaeology issues will be analyzed, both as measuring tools for the documentation of existing archaeological structures as well as tools of archaeology prospection, which are based on the appearance of the reflection of covered structures in images (i.e., the so-called marks).