Web-based dissemination of continuously generalized space-scale cube data for smooth user interaction

ABSTRACT

The Space-Scale Cube (SSC) model stores the result of a generalization process, that supports smooth scale transitions for map objects. The third dimension is used to describe geometrically the smooth transitions between objects at different levels of detail. Often-used map generalization operators fit in this SSC model. The 3D SSC model to derive 2D maps can be used in a mobile web client, where these days powerful graphics hardware is available. This article shows the steps needed for producing and disseminating SSC data with smooth transitions over the web. Firstly, we explain how SSC data can be obtained and subsequently be rendered by making effective use of the GPU. Secondly, we show how we organize data in chunks and how this ‘chunked’ data can be used for efficient communication between client and server. In the third place, we describe which operations can be used on the client side for deriving maps. Fourthly, the SSC also allows for (a) mixed abstraction slicing surfaces useful for highlighting specific regions by showing more detail and (b) near-intersection blending, which helps to prevent abrupt transitions while the slicing surface is in motion. Finally, we show how animated pan and zoom functionalities may be realized. A set of prototypes allows us to disseminate the data with smooth transitions on the web and in practice judge the effect of continuous generalization and animating the map image.

RÉSUMÉ

Le modèle du Cube Echelle-Espace (SSC) stocke le résultat dun processus de généralisation qui permet des transitions d'échelle fluides pour les objets cartographiques. Les opérateurs standards de généralisation cartographique s'intègrent dans le modèle SSC. Le modèle 3D SSC pour dériver des cartes2D peut tre utilisé dans un client web mobile. Cet article montre les étapes nécessaires pour produire et distribuer des données SSC avec des transitions fluides sur le web. En premier, nous expliquons comment les données SSC peuvent tre obtenues et restituées par une utilisation efficace du processeur graphique (GPU). Puis nous montrons comment organiser les données en morceaux et comment ces morceaux' peuvent tre utilisés pour une communication efficace entre le client et le serveur. En troisième lieu, nous nous décrivons les opérations qui peuvent être utilisées côté client pour dériver des cartes. En quatrième point, nous montrons que le SSC peut aussi permettre (a) d'extraire des coupes de surfaces de niveaux d'abstraction mixtes et (b) de créer des mélanges proche des intersections afin d'éviter des transitions abruptes lorsque une coupe de surface est en mouvement. Enfin, nous montrons comment les fonctionnalités de déplacements et zoom animés peuvent être réalisées. Un ensemble de prototypes nous permet de diffuser sur le web des données avec des transitions fluides et en pratique de juger de l'effet de la généralisation continue et de l'animation de la carte.

KEYWORDS:

• Map visualization
• continuous generalization
• real time
• interaction
• web mapping

Disclosure statement

No potential conflict of interest was reported by the authors.

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Notes on contributors

Martijn Meijers (1981) started his studies in Geodesy and Cartography at Utrecht University of Professional Education (Hogeschool van Utrecht), where he specialised in Geographic Information Systems. He continued his studies at Delft University of Technology, where he obtained a Master of Science degree in Geomatics in 2006. In 2011, he successfully defended his PhD thesis at this university on the topic of Variable-scale Geo-information. Currently, he is employed as Assistant Professor at Delft University of Technology, Department of GIS technology. Martijns research interests include map generalisation, geo-database management systems, cartography and geo-visualisation, (applied) computational geometry for GIS, handling large datasets and topological consistency.

Peter van Oosterom (1963) obtained an MSc in Technical Computer Science in 1985 from Delft University of Technology, The Netherlands. In 1990 he received a PhD from Leiden University on the topic ‘Reactive Data Structures for GIS'. From 1985 until 1995 he worked at the TNO Physics and Electronics Laboratory in The Hague where he was one of the developers of GEO++, an open GIS based on the Postgres DBMS. From 1995 until 2000 he was senior information manager at the Dutch Cadastre, where he was involved in the renewal of the Cadastral (Geographic) database. Since 2000, he is professor at the Delft University of Technology and head of the section ‘GIS Technology'. His research topics include: Spatial databases (point clouds), GIS architectures, Map Generalization, Vario-Scale, 5D Modeling, Querying and presentation, Internet/interoperable GIS and (3D) Cadastral applications. He is the current chair of the FIG working group on ‘3D-Cadastres’.

Mattijs Driel (1987) completed an MSc at Utrecht University in 2015 working on the visualisation of the Vario-Scale data structure for real-time applications, under the supervision of Prof. dr. ir. P.J.M. (Peter) van Oosterom, dr.ir. B.M. (Martijn) Meijers, and Prof. dr. E Eisemann. Following the completion, he diverted away from research to focus more on improving his software engineering, architecture and development skills. In the latter half of 2015 he started at Double Dutch Games helping to refactor their game's architecture to better support multi platform deployment. In 2016 switching to work at Twnkls (now a branch of PTC) to help and lead construction of, amongst others, the Ikea Place app. Currently, he is still employed at PTC.

Radan Šuba (1986) finished his studies in 2012 at the University of West Bohemia, in Pilsen, the Czech Republic, and obtained his Master degree in Geomatics. During his studies, he gained practical experience when he worked as a land surveyor. In 2012 Radan was appointed as a PhD candidate at the Delft University of Technology, the Netherlands, under the supervision of Prof.dr.ir. P.J.M. (Peter) van Oosterom and dr.ir. B.M. (Martijn) Meijers funded by the Dutch Technology Foundation STW (projectnumber 11185). He researched vario-scale maps: Alternative solution for obtaining and maintaining geographical data sets on different map scales. He focused on R&D to expand and to enrich current prototypes for automated map generalisation.

Notes

1 Screen casts:

• Intersecting an SSC in real time – https://vimeo.com/193857079 – user zooming in.

• Near-intersection blending – https://vimeo.com/193857089 – same zoom in action, but now with near-intersection blending activated.

• Non-planar slicing surface – https://vimeo.com/193857103 – user drags the blue dot over the map, a slice surface is used as shown in Figure 15(c). The result is that around the blue dot the map scale is larger and map objects of larger scale are connected seamlessly to surrounding objects of smaller scale.

2 Prototype III is available at https://varioscale.bk.tudelft.nl/ $▹$ ‘WebGL demo’.