Overview

Belgium has one of the largest and most diverse collections of built heritage in Europe, visited every year by millions of people. This patrimony is of exceptional cultural and economic importance for the country and its conservation is a priority at both federal and regional levels. Due to heavy industrial and urban development, the buildings suffer from physical, mechanical, chemical, and biochemical pathologies along their history. Furthermore, external human activities such as groundwater extraction, digging of underground galleries and temporary excavations may contribute to their structural instability. The adequate protection and preservation of built heritage therefore requires an integrated analysis of environmental, architectural and historical parameters.

The Royal Institute of Cultural Heritage (RICH) is the federal scientific institution dedicated to the study, conservation and development of Belgium's cultural heritage. The Royal Belgian Institute of Natural Sciences (RBINS) has a geology department (GSB) in charge of the study of the Belgian subsurface. Both institutes have their own databases, data types and methods of work. However, for an efficient preservation of the Belgian cultural heritage, collaboration and integration of data and knowledge are necessary. The project GEPATAR (GEotechnical and Patrimonial Archives Toolbox for ARchitectural conservation in Belgium) aims to improve the management of the federal patrimony by integrating data from the archives of RBINS and RICH and by assessing the stability of monuments using radar interferometry.

In the first stage of the project, a dedicated remote sensing image processing tool will be developed by the Centre Spatial de Liège (CSL) for the exploitation of the Synthetic Aperture Radar (SAR) satellite data archive available at RBINS. By creating PS-InSAR (Persistent Scatterer Interferometry) processing models, it will be possible to map ground movement trends at local and regional levels to an accuracy of millimetres. In short, radar waves emitted from satellite platforms are reflected by illuminated objects on the ground; the recorded return signals form a SAR image. In the case of ERS and ENVISAT, the satellites have a return period of 35 days for the same scene. It is then possible to “compare” the radar images acquired and calculate the movement of an object through the phase difference generated by the distance change between the satellite and the object. Integration of the PS-InSAR processing with the geological and geomorphological archive of RBINS will allow risk assessment of ground movements from local (i.e. individual buildings) to regional and national levels.

The GEPATAR toolbox will be created by the Signal and Image Centre of the Royal Military Academy (RMA) in a GIS environment, allowing the integration of data from the RICH and RBINS archives at three scales: national, regional and local. The integration of topographical, cadastral, land cover, geological, geomorphological and geotechnical data with historical, structural engineering and architectural information will allow risk assessment for the Belgian cultural heritage. At national and regional levels GEPATAR will provide the staff at RICH involved in defining conservation strategies with possibilities to prioritize conservation actions. At local level GEPATAR will provide all the necessary datasets to assess the risk for individual objects.

Evaluation of the GEPATAR toolbox will be done using specified case studies. The selected monuments are located in areas where intensive urbanism and post-industrial activities have occurred. A ground movement risk model will be developed for each building, for which a range of environmental, geographical, historical and architectural datasets needs to be collected. This information, combined in the GEPATAR modules, will be input to further structural engineering analysis at the Raymond Lemaire International Centre for Conservation (RLICC) of the KULeuven, where the strength of the building structures will be assessed.

WP1: Management, communication and dissemination activities

The project management (Task 1.1) is coordinated by RBINS. In order to ensure proper interaction between the partners, regular project meetings will be scheduled. A follow-up committee composed of national stakeholders, and known as European experts, will provide feedback on the progress of the project in terms of its overall strategy and technical implementation of its results. Dissemination of the project results will be done via this website (Task 1.2), at international conferences and through publication in peer-reviewed journals (Task 1.3). At the end of the project a dedicated workshop will be held to present the GEPATAR toolbox and the results to stakeholders and (potential) end-users (Task 1.4).

WP2: Ground deformation monitoring

This work package includes the development of the PS-InSAR chain tool and the processing and interpretation of the available PS-InSAR data.

PS-InSAR chain tool development and processing (Task 2.1):

• Definition of the technical and architectural requirements for the InSAR techniques;
• Development of the PS-InSAR chain tool into a software module;
• Testing and validation of the module on ERS and ENVISAT in Single-Look Complex (SLC) format, as available at RBINS;
• Adaptation of the module to future SAR formats (TerraSAR-X and Sentinel).

Analysis and interpretation of the PS-InSAR data (Task 2.2):

• Statistical analysis of the PS-InSAR data, resulting in annual average velocity values;
• Interpretation of ground deformations, using the data provided from Task 4.3;
• Creation of ground deformation hazard maps and vulnerability assessment of the cultural heritage, using input from WP3 and Task 4.3.

WP3: Stability analysis of the buildings, case studies

The objective of WP3 is to develop a stability analysis methodology for buildings, based on the geo-spatial risk assessment as derived from the PS-InSAR module. The methodology will be developed using selected case studies.

The first task of this work package (Task 3.1: Methodology assessment) is to identify relevant typologies of architecture and construction for which measured ground movements can result in stability problems.

This task will:

• Assure that the methodology is based on spatial and temporal scales relevant for the typologies of historic fabric;
• Evaluate the selected case studies towards their relevance to correlation between risks of damage and the collected geo-spatial data.

The selected case studies will be used to demonstrate the validity of the collected geo-spatial data for risk assessment of heritage buildings (Task 3.2). Based on engineering practice and ground deformation information a preliminary stability analysis will be carried out. The foreseen instability trend will be monitored in-situ during several months using fully automatic monitoring equipment.

WP4: GEPATAR toolbox for patrimony conservation

The main objective of WP4 is the creation of the GEPATAR toolbox in a GIS environment, allowing vector, raster and contextual data to be integrated at three spatial scales: national, regional and local.

The first task of this work package (Task 4.1: Definition of users and system requirements) is to assure that the developed tools will meet the end-users requirements. Best practice examples of cultural heritage monuments will be selected for testing and validation. The different modules of the GEPATAR system will then be defined based on the user requirements, selected case studies, and the format of the output from the engineering analysis and ground deformation hazard maps.

The main task of WP4 is the development of the GEPATAR toolbox (Task 4.2):

• Definition of the toolbox’s concept of operations (CONOPS), including the expected services and outputs, data integration and the expected performance of each tool;
• Development of several hierarchical fusion models that will allow integration of vector, raster and contextual data;
• Implementation of the toolbox in a GIS environment with integrated links to the RBINS and RICH archives and dedicated tools conforming to the predefined users requirements.
• Design and development of a geoportal which interactively displays information from the different source databases together with ground movement hazard maps and case studies.

The building heritage data available at RICH will be fully integrated in the GEPATAR toolbox (Task 4.3) in order to illustrate geographical distribution, typology, relevant historical information and images at different spatial scales. Also the instability information collected in the case studies will be integrated within the web-based portal.

Evaluation and validation of the toolbox (Task 4.4) will be done at an early stage to allow improvements and debugging before final delivery. Sustainability of the toolbox and geoportal will be assessed regarding future maintenance and data updates.

Expected research outcomes

GEPATAR aims the fusion between the archives of RBINS and RICH for a better management of the federal patrimony. A dedicated image processing toolbox will be created for the exploitation of the RBINS remote sensing archive. The output from this toolbox will be integrated with other national and regional spatial datasets for the analysis and visualisation of Belgian patrimony at risk, using the developed GEPATAR modules. The project data will be made accessible via a web-based geoportal.