E. Verbree

Interaction in virtual world views-linking 3D GIS with VR

To support 3D GIS interaction within VR-environments we propose a multi-view approach based on three types of visualization: plan view, model view and world view. The visualization in these views ranges from a conventional map, through a partly symbolic and simplified 3D representation to a full immersive and photo-realistic 3D display. The views can be used simultaneously or intermittently, and each provides a repertoire of interaction possibilities that are apt but not necessarily limited to that view. We are currently developing a 3D GIS&VR system (Karma VI) based on existing GIS and VR technology that uses the three views to support the design, development and presentation of large infrastructure plans in The Netherlands. Operational use of this system showed that the multi-view approach leads to a more sophisticated understanding of those plans.

A multi-view VR interface for 3D GIS

Abstract Virtual reality is becoming a popular tool to visualize 3D GIS data. Direct interaction with the GIS data, however, is often limited. In this paper, we present a multi-view approach to support 3D GIS interaction within VR-environments. The multi-view approach is based on three types of visualization: plan view, model view and world view. The plan view visualizes the data as a conventional cartographic map. The model view provides a 3D birds-eye view on a partly symbolic and simplified 3D representation of the data. The world view gives the full immersive and photo-realistic 3D display. These views or modes can be used simultaneously or intermittently, and each provides a repertoire of interaction possibilities that is apt — but not necessarily limited — to that kind of visualization and interaction. This multi-view approach is implemented in the Karma VI system, using existing GIS and VR technology. We describe the multi-view approach, the system components and the internal data models, and how CAD models can be imported and be made consistent with the GIS data.

Towards a National 3D Spatial Data Infrastructure: Case of The Netherlands

comers. Much relevant knowledge is only available at data providers and software vendors level which make it difficult to get an independent advice. On the other hand, the demand is not always clear which makes it hard for data providers and software vendors to offer demand-oriented products and services. Despite the slow progress of 3D in practice, it is clear that 3D applications are important and will become even more important in the near future. The world is 3D and consequently a 3D approach has better potentials for managing and planning public spaces (for example

Construction of the Planar Partition Postal Code Map Based on Cadastral Registration

Accurate postal code maps have many applications within GIS as the postal code has the potential to link the address description of buildings to their location in a specified global reference system in a more natural way. This relationship is possible in both directions: geocoding and reverse-geocoding. These operators demand a mechanism for translating an exact geometric position (i.e. WGS84 coordinate) into a location indication (town, street, house number) and vice versa. As most built-up parcels are provided with a postal code, this indicator can be used as the linkage. This paper describes the procedure, based on the Dutch cadastral registration, to obtain a reliable 6-position (i.e. 2628BX, the highest level of detail possible) planar postal code map for the Netherlands. Problems with existing, Voronoi-diagram based, postal code maps, like intersected houses and arbitrary derived (and thus unrecognizable) boundaries are avoided. The reliability of the derived planar postal code map is discussed and results are illustrated by figures. For a planar coverage, non built-up parcels having no postal code should be assigned a plausible postal code. Furthermore special attention is given to infrastructural parcels. These parcels are divided at their (approximated) skeletons first and then these subdivided infrastructure parcels are piecewise attached to their neighbour parcels. This new approach results in very reliable postal code maps, which are visually attractive too as infrastructure lines can be recognized. The procedure is generic and can be applied to other administrative parcel information as well. The algorithm is implemented using the Computational Geometry Algorithms Library (CGAL), and the possibilities and limitations of this library are addressed as well. Also a number of non-implemented alternatives or improvements are given.

Toward seamless indoor-outdoor applications: Developing stakeholder-oriented location-based services

Location-Based Services (LBS), an emerging new business based on smartphone and mobile networks, are becoming more and more popular. Most of these LBSs, however, only offer non-seamless indoor/outdoor applications and simple applications without giving stakeholders the chance to play an active role. Our specific aim is to solve these issues. This paper presents concepts to solve these issues by expanding the Open Location Services Interface Standard (OpenLS) to allow seamless indoor/outdoor positioning and to extend the content of the services to include information recommended by stakeholders.

Validation and Storage of Polyhedra through Constrained Delaunay Tetrahedralization

Closed, watertight, 3D geometries are represented by polyhedra. Current data models define these polyhedra basically as a set of polygons, leaving the test on intersecting polygons or open gaps to external validation rules. If this testing is not performed well, or not at all, non-valid polyhedra could be stored in geo-databases. This paper proposes the utilization of the Constrained Delaunay Tetrahedralization (CDT) for the validation (i.e. check on self-intersecting and closeness) of polyhedra on the one hand, and the efficient storage of valid polyhedra on the other hand. The paper stresses on the decomposition of a polyhedron through a CDT and the possibility to store and compose the polyhedron through the vertices of the CDT, a bitmap that indicates which faces of the Delaunay Tetrahedralization (DT) links to a CDT-face, and a list of non-recovered CDT-faces.

Towards a 3D Feature Overlay through a Tetrahedral Mesh Data Structure

The use of 3D features within GIS has been increasing due to the need to represent, query, manipulate, and analyze man-made objects in relationship to other 3D features related to the surface of the earth. This will yield an increased use of 3D boundary representations of the features. The spatial relationship between two or more features is often evaluated using a geometrical overlay of these features, which reveals whether these features overlap and—if they do—to which extent. We present the design of a 3D overlay algorithm which overlays 3D triangulated boundary representations through a constrained tetrahedral mesh. The intersections between the constrained facets of the 3D features are calculated on the fly and within a restricted neighborhood. We can identify and reconstruct the overlaid parts of the 3D boundary representation within the tetrahedral mesh. The implementation is based on the Computational Geometry Algorithms Library, which proved to have the functionality needed but also has its limitations.

Prediction of GNSS Availability and Accuracy in Urban Environments Case Study Schiphol Airport

Because of the increased call for positioning in urban areas, the performance of GNSS is analyzed under conditions with a decreased satellite visibility caused by buildings blocking the lines of sight. With GPS and Galileo almanacs and two city models visibility fi ngerprints of time-location combinations are computed. Outdoor availability and accuracy are predicted for both city models: Real-life data of Schiphol Airport, and an imaginary urban canyon model (located in the same area as Schiphol) with variable parameters for street width, street length and building block height. The accuracy is predicted based on dilution-of-precision values. GPS, Galileo, and a combined constellation are considered for single-frequency singleepoch positioning.

Processing 3D Geo-Information for Augmenting Georeferenced and Oriented Photographs with Text Labels

Online photo libraries face the problem of organizing their rapidly growing image collections. Fast and reliable image retrieval requires good qualitative captions added to a photo; however, this is considered by photographers as a time-consuming and annoying task. In order to do it in a fully automated way, the process of augmenting a photo with captions or labels starts by identifying the objects that the photo depicts. Previous attempts for a fully automatic process using computer vision technology only proved not to be optimal due to calibration issues. Existing photo annotation tools from GPS or geo-tagging services can only apply generic location information to add textual descriptions about the context and surroundings of the photo, not actually what the photo shows. To be able to exactly describe what is captured on a digital photo, the view orientation is required to exactly identify the captured scene extent and identify the features from existing spatial datasets that are within the extent. Assumption that camera devices with integrated GPS and digital compass will become available in the near future, our research introduces an approach to identify and localize captured objects on a digital photo using this full spatial metadata. It proposes the use of GIS technology and conventional spatial data sets to place a label next to a pictured object at its best possible location.

Positioning LBS to the third dimension

Computer technology has evolved to a position of being able to handle large three-dimensional (3D) data sets. The third dimension is already taken for granted for visualisation on desktop machines. All GIS/CAD vendors are offering extended 3D tools for navigation and exploration of data. NASA World Wind and Google Earth demonstrate the possibilities of 3D to all users of the Web. The advances in geoDBMS are also striking; main stream DBMS support spatial data types, which can be adapted for handling of 3D data.