3D building model as an interface for a Web Information System. Case study of the Pontonniers high school in Strasbourg

The paper presents the results of a test study based on 3D modelling of the “Pontonniers International high school in Strasbourg” where the Alsace Region Institution asked for building documentation in order to proceed to a complete diagnosis to conform to the current regulation (detection of asbestos and lead, fire safety, heating systems, electricity, accessibility, etc.) as well as to insure the future of the patrimony and among other the general maintenance of roofs and facades. The diagnosis and statements campaigns are usually based on maps and photos, which are used to locate damaged elements. However, aware of the possibilities offered by photogrammetric techniques, we found it interesting to integrate these methods in the diagnosis process. A 3D model of the buildings of the site seems essential for further analysis and studies, providing georeferenced data for the user and visualisation in order to know the state of the buildings and to planify the management of works. The link with a database describing the patrimony's referential will be used to find existing maps, overall photos as well as zooms on details and other alphanumeric data, by browsing in the 3D model. To build a consistent geometric 3D model, we use on one side architectural information of the building, and on the other side dimensional data. Architectural knowledge based on analysis and overall documents leads the drawing of the model, without any scale in this first step. Only the shapes and the completeness of the model are aimed at this stage. To reach this goal, the Sketchup software package dedicated for designing buildings has been used. The integration of dimensional data is only done in a second stage, based on former geometric elements defined as specifications of the architectural knowledge. The scaling of the model is thus not dependent on the used techniques which can be surveying, photogrammetry or lasergrammetry. VRML textured models of the buildings result from this process. For the textures, orthophotos previously prepared for the companies in charge of the diagnosis are used. This 3D model is used as a browsing interface in the Information System of the Pontonniers high school in Strasbourg for handling all the available data. For the managers of the site, the model will also be used to modify and update the database. From a technical point of view, this information system is based on an EasyPHP server, allowing the creation of databases in MySQL, and interaction between the databases within PHP software packages. The 3D model is described in VRML, mostly used for the visualisation of 3D scenes on the Web. The realisation of the 3D model is prior to any following step. An anchor is defined for each face, which helps for its identification and its interaction. Any face of the model can thus be accessed, by consultation or in order to modify the corresponding tables in the MySQL database. All architectural data described above will be integrated in the overall database of the Region Alsace Institution for the management of the high schools of the Region. The interfaced 3D model can thus be used to reach any type of information from this database (as for example annual payment, representatives, cadastral data, companies, safety, etc.) by PHP software packages written to generate HTML pages. The update of the database is therefore possible directly from browsing in the 3D building models