Chryssy Potsiou

Towards a strategy for control of suburban informal buildings through automatic change detection

The problem of informal settlements is of significant importance and has similar causes worldwide. In Greece, such buildings are relatively well built and number nearly 1,000,000 across the country. This social and economic issue requires a combined approach. In this paper, a proposed solution to this problem is developed at a technical and administrative level, taking into consideration the criteria of least possible cost and maximum benefit from usage of modern technology. The basic idea is the development of a system that allows for periodic, automatic monitoring and detection of new buildings. With additional field control applied only to specific locations, immediate detection of informal construction projects prior to completion is enabled, at which time measures to halt their development can be more easily taken. The suggested procedure is based on the use of high resolution images and the application of automatic change detection by computation and comparison of digital surface models and building extraction techniques. Results from a pilot application of the proposed procedure are given together with an estimated cost for application of this method to the coastal zone of eastern Attica, a Greek prefecture with many existing and emerging informal constructions.

VGI in Cadastre: a Greek experiment to investigate the potential of crowd sourcing techniques in Cadastral Mapping

Abstract What make citizens participate in mapping projects? What motivates them to get involved in a non-hierarchical network of individuals who collect, edit and share geospatial data? Would they be willing to participate in cadastral mapping as an alternative way to speed up the cadastral survey and minimise the costs and errors which rise when traditional procedures allow limited owners’ participation? The answers are still ambiguous. However, it is a fact that the way geospatial data are used and the way citizens comprehend its importance have changed dramatically during the last years. The paper briefly gives an introduction on the evolution of Neogeography and the citizens’ involvement in spatial data collection, editing and uploading on the web, and of the introduction of the term volunteered geographic information (VGI) and its adoption by the scientific community. The paper then presents the first results of an academic research being compiled at NTUA in collaboration with FIG Com3 WG 3·2. focusing on the investigation of the potential for intergrading crowd sourcing techniques to create draft cadastral maps. The application area chosen for the experiment is the rural part of the village ‘Tsoukalades’, on the Greek island of Lefkada. Fifteen volunteer land owners participated to a weekend experiment and collected geospatial data for the delineation of their land parcel boundaries on a cadastral map; the spatial data were collected with the aid of a handheld GPS after a brief training; the resolutions from the interviews with the land owners and the resulting citizens’ cadastral map are presented.

Selective 4D modelling framework for spatial-temporal land information management system

This paper introduces a predictive (selective) 4D modelling framework where only the spatial 3D differences are modelled at the forthcoming time instances, while regions of no significant spatial-temporal alterations remain intact. To accomplish this, initially spatial-temporal analysis is applied between 3D digital models captured at different time instances. So, the creation of dynamic change history maps is made. Change history maps indicate spatial probabilities of regions needed further 3D modelling at forthcoming instances. Thus, change history maps are good examples for a predictive assessment, that is, to localize surfaces within the objects where a high accuracy reconstruction process needs to be activated at the forthcoming time instances. The proposed 4D Land Information Management System (LIMS) is implemented using open interoperable standards based on the CityGML framework. CityGML allows the description of the semantic metadata information and the rights of the land resources. Visualization aspects are also supported to allow easy manipulation, interaction and representation of the 4D LIMS digital parcels and the respective semantic information. The open source 3DCityDB incorporating a PostgreSQL geo-database is used to manage and manipulate 3D data and their semantics. An application is made to detect the change through time of a 3D block of plots in an urban area of Athens, Greece. Starting with an accurate 3D model of the buildings in 1983, a change history map is created using automated dense image matching on aerial photos of 2010. For both time instances meshes are created and through their comparison the changes are detected.

Enhancing cadastral surveys by facilitating the participation of owners

Abstract While some countries have over centuries developed a nation-wide spatial framework, some others have been left behind. However, because of the global economic and social challenges, there is an urgent need for those countries to develop similar systems in a fast and efficient way for their economic survival. Building such a framework should be always based on each countrys resources and capacities. In systematic cadastral registrations, the participation of owners has always been crucial for the success of the project. Within this concept, the authors investigate the potential of new tools to increase the participation of land right holders and local volunteers (non-professionals) and to enhance the cadastral surveying procedure. A hybrid “crowdsourcing” approach is proposed, mainly based on the direct participation of property rights holders in which the role of the cadastral surveyor is crucial. A commercial application for smartphones is tested. The smartphones GPS is used only for the general positioning on the basemap to avoid gross errors when owners are not accustomed in using aerial photos. A recent orthoimage of 20 cm pixel size in urban areas and an orthoimage basemap of 50 cm pixel size in rural areas is used as the basemap. Once roughly positioned, owners may then digitise the boundary coordinates on the basemap off-line, with little training support; they may also work from a distance. In areas where the property boundaries are easily recognised on the basemap, boundary coordinates have the expected geometric accuracy that can be achieved on the basemap while no gross errors are detected. Attachment of photos is also possible (e.g. photos of the property or of the deeds). Restricted access to personal data may also be achieved. The method is also useful for cadastre updating purposes (e.g. the periodic updating of buildings database).

OpenStreetMap for cadastral purposes: an application using VGI for official processes in urban areas

Abstract The scope of the paper is to test if the online dynamic maps such as the OpenStreetMap (OSM) can be used for official mapping projects such as Cadastre, to investigate the advantages and the concerns of online and open to the public procedures and to identify those differentiations between experts and amateurs that play a critical role in such official projects. The specific research is focused on the use of OSM in urban areas as an alternative method to the official cadastral surveys. This paper presents the possibilities and the perspectives of OSM for spatial and attribute cadastral data collection and storage for the compilation of draft cadastral maps as an alternative methodology within the terms of the volunteered geographic information (VGI). The authors carried out a practical experiment in an extended part of the historic city centre of Athens and updated the online dynamic map of OSM with attribute and spatial cadastral data. Surveying students explored the capacities of the dynamic map in two steps: (a) in a section where the polygons of the buildings already existed on the map, they had to improve it with attribute data, and (b) in another section where no relevant polygons existed, a spatial and attribute data enhancement was required. The research was based on the various approaches that each student adopted and the freedom that the OSM offers to the users. The results show that users can easily distinguish the differences in capacities between the OSM and the commercial software; the inexpensive, easy to use and quick methodology of the OSM in contrast to the accurate, authoritative and assured methodology of the commercial software.

Hellenic cadastre: state of the art experience, proposals and future strategies

Abstract In 1994, the Hellenic government, with the support of the European Union, started a project for the establishment of the Hellenic Cadastre (HC), which will be a title registration information system in fully digital form. It is estimated, that this project will last 20 years and it will cover the whole country. So far, digital photogrammetric Cadastral Surveys (CSs), named Pilot Phase and Main Program, of a total area of 893,000 ha have been commissioned and executed in various areas of Greece; 250,000 ha more were commissioned within the year 2000. Through this work, a surprisingly high level of cooperation between the private and public sector has been achieved. This paper focuses on the research and the progress that has been made in all scientific fields, such as the definition of the content of this project, the implementation of the responsible institutions/agencies for the HC, their administrative structure, the proposed regional structure, the development of the National Legal Framework for the compilation of the CSs, the adjudication procedure and maintenance issues. An emphasis is given to the experience so far gained in the legal and technical aspects, and especially to the proposals for an improvement of the methods, and to the attempt to create a cost recovery business culture for maximizing the products and services, which can be supported by the HC. This project requires major international and local experience and a high level of research in all the above mentioned issues, which has to be applied successfully.

5D multi-purpose land information system

The complexity of modern urban environments has led to the introduction of 3D Land Information Systems (LISs), which tend to replace traditional 2D LIS architectures for the purposes of urban planning and regeneration, land administration, real estate management and civil development. Both the need for 3D visualization of the geometry of buildings in various time instances through the years and the need for acquisition of 3D models in various levels of detail (LoDs), which not only fulfill the requirements of the various users but also they speed up the visualization process, are obvious. Thus, additional dimensions, that is, for time and scale, need to be supported by a modern LIS. This paper introduces a 5D modelling pipeline that may be adopted by a multi-purpose LIS for the selective creation of 3D models of an urban area in various time instances and at various LoDs, enriched with cadastral and other spatial data. The methodology is based on automatic change detection algorithms for spatial-temporal analysis of the spatial changes that took place in subsequent time periods, using image orientation, dense image matching and structure from motion algorithms; the procedure requires photogrammetric stereo plotting, implements procedural modelling and relies on the availability of overlapping aerial and terrestrial imagery, ground control points and cadastral information. Finally, an application based on the proposed methodology in an urban area in Greece is presented and the future work is discussed.

A new model for cadastral surveying using crowdsourcing

A ‘fit-for-purpose’ approach is developed, tested and presented for cadastral surveys through increased owners’ participation using new technology and m-government services. Three case studies are reported, for urban, suburban and rural areas, with a combined use of two mobile applications: a commercial software package (ESRI’s Collector for ArcGIS) and an opensource self-developed application named BoundGeometry. The parameters of time, quality and accuracy are assessed and the identified difficulties are classified. It is concluded that the method is applicable both in developed and developing countries, and each time adjustable to the available infrastructure.

A Spatial Information System for the Archaeological Site of Mycenae

Digital and automated photogrammetric procedures, developed for the collection and management of spatial data, and terrestrial laser scanning systems provide new capabilities for documentation of archaeological monuments and sites. Also, special tools in Spatial Information Systems and production of virtual models have been developed. Their combination provides relevant scientists (architects, archaeologists, etc) and users with a variety of options for the creation of integrated systems capable for documentation, restoration and cultural development of archaeological sites. Detailed 2D and 3D representation of the current condition of the site, development of a multi-purpose SIS, and introduction of modern digital products at a local museum, such as 3D models, creation of virtual environment and Web applications are some of them. Application of such techniques and systems was made to the archaeological site of the Mycenae in Greece, one of the most important sites worldwide.

Security of ownership versus public benefit: a case study for land taking for infrastructure in Greece, as an EU member state

Abstract This paper presents the results of a 4 year research (Internet, existing literature, interviews with experts from the public and private sectors, Ministry records) on the general legislative and technical aspects and the procedures implemented in Greece, an European Union (EU) member State since 1981. It is a study of compulsory land acquisition and is a case study focused on collecting and analysing recent information about land taking procedures and practices in Greece with an emphasis on current major highway projects. Included is a study of the legal framework; the legislative amendments adopted progressively through recent years; and the existing conflicts among the various Greek courts and the Court of Justice of the European Union and between interpretation of the Greek legislation and the practices in free market economies. Additional problems with the land acquisition process are investigated. This case study focuses on the investigation of emerged problems, and the legislative changes made, due to pressure for a number of major infrastructure projects for the 2004 Olympic Games and motorway projects commissioned by the Hellenic Ministry of Infrastructure, Transport and Networks. These consist of major transportation road networks in the areas of Northwestern Greece (Ionia Odos), North Greece (Egnatia Odos), Attica peninsula (Attiki Odos) and the Peloponnesus (Olympia Odos). An effort is made in this study to develop strategic recommendations for improving the protection of private property in Greece; harmonising land expropriation practices with the European approach; and for simplifying and accelerating the adjudication process and the achievement of more transparent and just compensation.