The 3rd ISPRS Workshop on Dynamic and Multi-Dimensional GIS & the 10th Annual Conference of CPGIS on Geoinformatics

Chen, Jun

Bibliographic data

Monograph

Persistent identifier:: 856566209

Author:: Chen, Jun

Title:: The 3rd ISPRS Workshop on Dynamic and Multi-Dimensional GIS & the 10th Annual Conference of CPGIS on Geoinformatics

Sub title:: May 23 - 25, 2001, Bangkok, Thailand

Scope:: VI, 434 Seiten

Year of publication:: 2001

Place of publication:: Pathumthani, Thailand

Publisher of the original:: AIT

Identifier (digital):: 856566209

Illustration:: Illustrationen, Diagramme, Karten

Language:: English

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2016

Document type:: Monograph

Collection:: Earth sciences

Chapter

Title:: 3D MODELLING FOR AUGMENTED REALITY. Siyka ZLATANOVA

Document type:: Monograph

Structure type:: Chapter

ISPRS, Vol.34, Part 2W2, “Dynamic and Multi-Dimensional GIS’’, Bangkok, May 23-25, 2001 The result is a list of co-ordinates structured according to the order of the faces and order of the nodes in a face. To create the VRML file, the data set obtained with these queries has to be further structured according the VRML model. In our example, two options are possible to represent the faces constructing the POLYHEDRON 23 in VRML, i.e. they can be stored as individual faces or as a part of one polyhedron. The first option is simpler and can be derived directly from the SQL query. The second representation requires control of duplicated co-ordinates and the correct ordering of the corresponding co-ordinates in the description of the faces (i.e. in the VRML node coordlndex). Currently, we concentrated on development of operators that create a VRML file consisting of objects (i.e. not individual faces). Since standard SQL statements cannot perform this operator, the computations have to be completed with the help of a host language (PL/SQL, C++, Java). At this stage, we have used PL/SQL, i.e. the script language provided by Oracle. A number of tests aimed at clarification of the best mapping and fastest operators to retrieve the needed data. For the purpose the first tree mappings discussed in the paper are implemented and populated with data. The corresponding VRML creators are tested for performance. Although the data structure is at very initial stage, the first results are very encouraging: 20 000 faces (part of 1600 buildings) can be retrieved in less then 23 seconds for representation with nested tables and less then a second for the relational representation and object-oriented views. The conditions of the test and the data sets are reported and discussed in more details in [17]. In principal, we expect less data to be extracted for rendering, i.e. the objects that are visible only from the current position of the user. These data are estimated in the range between 50 and 5000 faces if spatial search is applied. This is indication for a possible further improvement of the obtained results. 7 CONCLUSIONS We have presented a 3D topological structure that provides data for a real time application i.e. serves two tasks (pose determination and rendering of virtual objects) that require real time commuting. The proposed structure maintains four abstractions of geometric representation (the ones mostly employed in 3D modelling) based on two constructive elements (faces and nodes). To be able to provide “cheap” details in terms of line features, the model incorporates non-topologically organised data, i.e. lines. Explicit relationship links a set of lines to a face. To be able to achieve the required accuracy and to build the 3D topology, a number of 3D reconstruction methods are applied. The model is implemented in relational database Oracle utilising relational and object-relational mappings. Several operators to create a VRML file are created and tested. The experiments clearly show that a 3D topological model can be adopted for an augmented reality application. The performance of the mappings in relational database drops bellow the required 6 seconds. The methods utilised in the 3D reconstruction ensure accuracy of few decimetres that is agreed to be sufficient for the positioning system. Therefore we consider the results reported in this paper a successful step toward a 3D GIS supplying data for a real time application. Still more experiments are needed to clarify the relational mapping that will assure the best performance. Currently, the SQL queries are executed from the Oracle high-level language that cannot be integrated in the UbiCom architecture, i.e. C++ modules have to be developed and further tested. Location and efficient spatial search in such large databases can not be performed without appropriate spatial indexing. One of the directions for further research within the project is related to developing a set of specific operations than will reduce the amount of data transmitted to the vision system. Examples of such operators are determination of the area of interest (using approximate positioning obtained by the mobile equipment), back-face culling (to eliminate invisible faces) and a variety of line filters for retrieval of line features. References [1] Abiteboul, S and R. Hull, 1987, IFO: A formal semantic database model, ACM Transactions on Database Systems, Vol.12, No.4, pp. 525-565 [2] Bodum, L., I. Afman and J. Smith, 1998, Spatial Planning moves out of the flatlands, AGILE, 23-25 April, Enschede, The Netherlands, CD-ROM [3] de la Losa, A. and B. Cervelle, 1999, 3D topological modelling and visualisation for 3D GIS, Computers Graphics, Vol.23 [4] Kofler, M. and M. Gruber, 1997, Toward a 3D GIS Database, GIM, Vol. 11, No. 5, pp. 55-57 [5] Molenaar, M., 1990 A Formal Data Structure for 3D Vector Maps, Proceedings of EGIS’90, Vol. 2, Amsterdam, The Netherlands, pp. 770-781 [6] OpenGIS specifications, 2000, available on http:. ;/ www.openqis.orq/techno/'specs-htm [7] Pasman, W., A. van der Schaaf, R.L Lagendijk and F.W. Jansen, 1999, Low latency rendering for mobile augmented reality, Proceedings of the ASCI'99, 15-17 June, Heijen, the Netherlands, pp. 372-376 [8] Persa, S and P. Jonker, 1999, On Positioning Systems for Augmented Reality Applications, Handheld and Ubiquitous Computing 1999, Springer Lecture Notes in Computer Science 1707 [9] Pilouk, M., 1996, Integrated Modelling for 3D GIS, PhD thesis, ITC, The Netherlands, 200 p. [10] Pigot, S., 1995, A Topological Model for a 3-Dimensional Spatial Information System, PhD thesis, University of Tasmania, Australia, 228 p. [11] Ubicom project, 2000, available on http://bscw.ubicom.tudelft.nl:' [12] van Oosterom, P., 1997, Maintaining consistent topology including historical data in a very large spatial database, Auto Carto 13, April, Seatle WA, pp. [13] Verbree, E., G. van Maren, R. Germs, F. Jansen and M.J. Kraak, 1999, Interaction in virtual world views—linking 3D GIS with VR, Int. J. Geographical Information Science, Vo!13, no 4, pp. 385-396 [14] The Virtual Reality Modelling Language, 1997, available on http:7www.web3cl.orq. , technicaiinfo/specifications/vrinl97.-in dex.htm [15] Zlatanova, S., 2000, 3D GIS for urban development, PhD thesis, ITC public. 69, Enschede, The Netherlands, 222 p. [16] Zlatanova, S., J. Paintsil and K. Tempfli, 1998, 3D object reconstruction form aerial stereo images, Proceeding of the 6th International Conference in Central Europe on Computer Graphics and Visualization'98, 9-13 February, Plzen, Czech Republic, pp. 472-478 [17] Zlatanova, S. and E. Verbree, 2000, A 3D topological model for augmented reality, Proceedings of the Second international symposium on MMSA, 9-10 November, Delft, The Netherlands, pp. 19-26 BIOGRAPHY Siyka Zlatanova: MSc degree at the University of Architecture, Civil Engineering and Geodesy, Sofia, Bulgaria in 1983 (Geodesy and Photogrammetry). PhD degree at the Graz University of Technology, Graz, Austria. Currently, a post-doctoral researcher at the Delft University of Technology, Delft, The Netherlands. Research field: Spatial Data Handling, 3D topology, 3D object reconstruction and visualisation.

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