Integration of 3D Geoscientific Visualisation Tools with help of a Geo-Database Kernel

Visualisation and the handling of large data sets are key issues in the workflow of many applications in today’s life and engineering sciences. However, from a software and data engineering point of view, these two important services are often located in two separated, i.e. independent and closed software systems. This means that the exchange of data and operations between software systems, i.e. the visualisation of database queries and the storage of visualised objects in the database management system, respectively, are not well integrated into many applications systems. We present an open CORBA-based system architecture that connects two existing geoscientific software tools – the geological 3D modelling and visualisation tool GOCAD and the geophysical 3D modelling tool IGMAS – via a 3D Geo-Database kernel, GeoToolKit. The common geo-scientific objects in the database can be accessed from GOCAD and IGMAS. The advantage of this method is that the 3D modelling tools can remotely access not only data but also the 3D advanced geometric database operations of GeoToolKit. Moreover, using the standard middleware platform we make the database and data also accessible for other applications. We report about our experience of the implementation with ObjectStore ODBMS and a CORBA/ODBMS adapter. Implementation aspects and open problems are discussed. 1 Motivation The necessity of an interconnection between geoscientific modelling software and database systems is recognised and accepted since many years. Nevertheless, the integration of geoscientific modelling applications and databases, allowing a direct access from the modelling software onto the database system and vice versa, is not a standard within geoscientific applications. Usually, not only one geoscientific application, but also varieties of applications are used for modelling, validation or visualisation of a specific area. Therefore, each of these applications interacts with each other by the exchange of data. The storage and management of all these data in separate files is a common method, though it is hazardous. At this, small scripts have to be written to convert a data set from one application to another. The representation of data 1 This work is funded by the German Research Foundation (DFG) within the collaborative research centre SFB350 at Bonn University and the joint project ”Interoperable geo-scientific information systems”. 2 GOCAD geological 3D modelling tool. http://www.ensg.u-nancy.fr/GOCAD/ 3 Interactive Gravity and Magnetic Application System (IGMAS) 3D gravity and magnetic modelling program http://userpage.fu-berlin.de/~sschmidt/Sabine_IGMAS.html 4 GeoToolKit geometrical 3D kernel of the spatial ODBMS GeoStore. http://www.geo.informatik.unibonn.de/software/GeoToolKit 6th EC-GI & GIS Workshop “The Spatial Information Society Shaping the Future Lyon”, France, 28-30 June 2000 into different formats leads to a redundant storage of data. It is (a) memory intensive and (b and more important) might lead to working on the “wrong” data. The use of DBMS as storage for the common spatial data has several advantages for the support of geoscientific modelling, e.g. an automatic integrity control. Spatial and temporal data can be tested against their semantic plausibility. The integrity checks can be executed during the reading of the data into the database or during the execution of database queries. Last, but not least, security mechanisms guarantee data security. The paper is organised as follows. In chapter 2 we briefly introduce an object-oriented 3D-4D spatial database GeoStore and the application design technology evolved on top of GeoToolKit. In chapter 3 we introduce extensions to GeoToolKit’s data model, which allow storing common data from two geomodelling tools GOCAD and IGMAS. A CORBA-based system architecture that integrates both systems with the database into one distributed 3D GIS is presented in chapter 4. This chapter also discusses existing CORBA/ODBMS integration techniques for providing distributed support for existing databases. A short overview of our approach to CORBA/ODBMS integration based on the eXtensible Database Adapter (XDA) is presented. Chapter 5 presents the evaluation of the integrated system and outlines some possible future developments and the last chapter summarises the contributions of this article. 2 Case Study In our case study the coupling between 3D-modelling tools through an object-oriented geodatabase kernel system was implemented to support a new method for the generation of geological maps. The geoscientific goal of this research was the development and implementation of a method, which allows the construction of plausible geological maps. At this, the geological map is generated by the cut of a 3D stratigraphical model with a digital elevation model (DEM). The 3D model serves also as input for subsequent investigations, e.g. numerical simulations on kinematic or dynamic models, by which an additional control of the generated 3D model is possible. In the study presented here, the geological 3D model is validated by an iterative exchange between geological and geophysical modelling tools to ensure geoscientific consistency. Here, besides GOCAD – a 3D geological modelling tool, an additional, geophysical application IGMAS is used to provide further constraints for an iterative revision of the 3D model and thus a succeeding modification of the geological map. For this reason, the 3D stratigraphic model, which is used as base model for the subsequent 3D gravity modelling using IGMAS and served as input for subsequent steps of validation using gravity and susceptibility data. However, the description of the iterative validation of the 3D model is not subject of this paper. It can be found in (Breunig et al. 1999). 3 GeoStore a common object-oriented spatial DBMS The integration of both (GOCAD and IGMAS) tools through a common Geo-Database enables the consistent handling of both, data and 3D models (and parts of it) during the geoscientific modelling process. The advantages, which arise by the use of the common database, are manifold, concerning not only the management of data and models but the management of multi-user access as well. At this, the most important aspects are (a) a central management of all data, (b) a simplified incorporation of new data, resulting in an implicit actualisation of the data, instantly visible to all participating editors and (c) update support of queries of data and models. 6th EC-GI & GIS Workshop “The Spatial Information Society Shaping the Future Lyon”, France, 28-30 June 2000 As a basis for development of a common data store it was reasonable to use the existing geodatabase system GeoStore developed within the collaborative research centre SFB350 at the University of Bonn (Bode et al. 1994). The intention of GeoStore was to supply geoscientists with a tool, which would provide the consistent storage and efficient access for data involved in all stages of the interactive 3D modelling process (Siehl 1993). The first version of GeoStore was implemented on top of the RDBMS Oracle. However, because of the complex structure of spatial data with multiple interlinks between objects, the object-oriented data model turned out to be more suitable for the development of a database. Consequently, GeoStore was completely re-implemented with the ODBMS ObjectStore (ODI 1997). The first step towards interoperation between the geological and the geophysical 3D modelling systems (GOCAD and IGMAS) was the development of a common object model. The most important requirement here was that geological and geophysical representations for the same entities might differ both in thematic attributes and in representations for geometric and topological data. The diversity of representations arises from the distinct purposes they serve for. Thus, in IGMAS data structures are optimised for the efficient mathematical computations while in GOCAD classes are oriented toward an efficient geometric editing and visualisation. 3.1 GeoToolKit – geometric database kernel Therefore, to meet the requirements of geoscientists occurring during the construction of 3D models, a common database model should be general enough to allow the integration of data types from both applications. To provide a non-redundant maintenance and cooperative utilisation of data by different applications developed within the interdisciplinary geoscientific research centre at Bonn University, the geometric kernel of GeoStore’s class hierarchy is separated from the other functionality in an independent library GeoToolKit (Balovnev et al. 1997).