Interactive Real-Time Vr Cartography

INTERACTIVE REAL-TIME VR CARTOGRAPHY

Manfred F. Buchroithner

Institute for Cartography, Dresden University of Technology, D-01062 Dresden, Germany Man- [email protected]

ABSTRACT

In October 2003 the Gesause National Park was founded in the eastern Austrian Alps. It was planned to realise an up- to-date information system for the visitors by combining of a classical solid relief model with interactive tools for the individual virtual reconnaissance of an area of approximately 300 km².

For the real-time visualisation, and animation a virtual 3D model with a horizontal resolution of 10 metres, a height accuracy of 1 metre, and a spatial resolution of the true-colour image data of 1,25 metres was generated. In a second step associated information was integrated. This covers texts, images, sounds and movie clips arranged in html- documents. A virtual helicopter overflight allows the materialisation of interactive real-time VR cartography.

1 INTRODUCTION

Today, photorealistic virtual reality and symbolised topographic cartography are frequently seen as antipodes. However, we believe that both categories can be well combined. If this combination is then still augmented by the third dimen- sion, interactivity and the possibility to change the user's viewing angle in real time, an optimum display of geoinforma- tion can be reached. Within the scope of the present project a team of geoscientists and engineers tried to come close to this target.

User-tailored state-of-the-art visualisation is nowadays a must not only in geosciences in general but for national parks in particular. For many years the Institute for Cartography of the Dresden University of Technology has been involved in the cartographic "conditioning" of geodata for various national park administrations. In October 2003 the youngest of the national parks in the Alps was founded: the Gesause National Park. It is situated in the Federal State of Styria in the eastern Austrian Alps. It comprehends high-alpine terrain with deep canyons incised into a landscape of mainly lime- stone and dolomite rocks. The foaming Enns River flows through the major canyon, the so-called Gesause (from Ger- man whizzing). To the north and the south it is surrounded by peaks reaching up to 2369 m (Hochtor Summit). Vertical drops up to 1800 m form the basis for famous and difficult rock climbs with up to 1000 m in height.

Due to their experience in three-dimensional visualisation and high-end cartography the National Park Administration contracted the Institute for Cartography together with the Awaron Company, Wiesbaden and Karlsruhe (Germany, www.awaron.com) to materialize new ways in cartographic design.

2 MOTIVATION AND BACKGROUND

Two major questions represented the basis for the considerations regarding an optimum visualisation of geodata in the Visitor Centres of the Gesause National Park:  How can the overwhelming beauty of the landscape and all the habitat peculiarities be presented in an informative and challenging way?  How can the local population be motivated to come to the Visitor Centres in order to obtain information about the current programmes and events organised by the National Park Administration?

The answer to both questions was a free flight over the National Park for all visitors of the Information Centres.

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Since the opening of the major Visitor Centre in Admont the biggest settlement in the sparsely populated Gesause Na- tional Park, on 26 October 2004 every visitor has the chance to explore the National Park from air, that is to say through a virtual flight. This flight has been materialized through the interaction of a "classical" physical relief with a colour airphoto mosaic draped over it and complex computer technology. The physical relief model, sized 200 cm x 300 cm and representing approx. 300 km² of terrain, stems from the Solid Terrain Modeling Company, Fillmore, California (www.solidterrainmodeling.com). The pilot's field of view is visualised on a vertical wall screen of 150 cm x 200 cm mounted behind the solid terrain model (cf. Figure 1). The installation offers several possibilities for the visitor to explore the National Park which are described in the following chapter.

Figure 1. Setting of the installation in the Visitor Centre of the Gesause National Park in Admont with the operator’s console in the foreground, the solid terrain model in the centre, and the wall screen for the display of the overflight view from the “virtual helicopter" in the back.

3 MODES OF CARTOGRAPHIC VISUALISATION

3D Flight

Like one of the many eagles living in the Gesause National Park, the visitor can enjoy a virtual flight through the landscape. In fact the four partners responsible for the development of this installation based the software which had to be developed on the simulation of a helicopter flight with a fixed camera looking straight down from the cockpit at an angle of 45 degrees. Many Points of Interest (PoIs) like mountain summits, settlements and marked trails carry a label in the form of a name-tag. These labels can be activated and, through this, additional information concerning the respec- tive PoIs can be retrieved. This collateral information exists in the form of texts, still images and short video sequences with sound tracks, realised as HTML documents (cf. Figure 2). For the sake of an easier orientation a light spot, point- ing into the nadir of the virtual helicopter, indicates the viewer's position on the solid terrain model. In order to prevent crashes of the "virtual pilots" against the ground or one of the steep vertical rock-walls, a minimum distance holder (buffer) of 300 meters has been implemented. Additionally, a "smoothing algorithm" prevents that, when flying in the minimum-distance mode, an angular movement of the aircraft with sharp changes in vertical direction occurs.

The navigation system is highly complex, but user-friendly. It is based on the solid terrain model functioning as a virtual mouse-pad, the mouse being realised by a beamer which gives an illumination point for the actual position.

Relief Flight

The term "relief flight" actually stands for a fast move over the terrain, so-to-speak a very low-level helicopter flight at the permitted minimum distance. Here, the visitor steers a light spot over the solid terrain model which, again, disposes of light spots at prominent points like the before mentioned mountain summits, settlements and marked trails. If the observer superimposes her/his moveable light spot with the light mark of one of these PoIs, the collateral information mentioned above will be displayed.

Hiking Trails

The hiking trail mode offers the visitor information about the network of marked hiking trails in and around the Gesause National Park. Here, the course of the trails can be draped over the virtually viewed terrain and displayed on both the solid terrain model and the wall screen. This allows to get e feeling for the extreme exposure of some of the marked trails like the famous Peter's Trail which even requires some basic climbing skills. This very realistic visualisation might even help to prevent alpine accidents.

Figure 2. The labels of the Points of Interest (PoIs) in the form of “name-tags” can be activated on the fly.

4 USER FRIENDLINESS AND SPECIFICATIONS

In order to motivate the visitors and to facilitate the immersion into the fantastic mountain landscape of the National Park, the Verdandi Company for Exhibition and Museum Planning, Vienna and Klagenfurt (Austria, www.verdandi.at) aimed at a multimedia installation. From the very beginning of the planning, a high degree of user friendliness was in the focus of all considerations of all four partners: the Gesause National Park Administration, Verdandi as the main contractor for the whole furnishing of all three visitor centres, and the Institute for Cartography of the Dresden Univer- sity of Technology in close cooperation with the Awaron Company, Wiesbaden and Karlsruhe (Germany). Awaron provided an unreleased version of their high-level virtual reality software Tucan which, for years has been in use at the

Dresden University of Technology. For this particular project, however, several new features had to be programmed. An advantage of the realised system is the possibility to update both geometry and image models and the tourist information in a simple way.

The operation of the system had to be designed that easy that also children have no difficulties in handling the com- mand interface of the installation, a joystick. The solid terrain model is located in the centre of the facility. On one side is the vertical wall screen located, on the other side the operator's console (cf. Figure 1). A pedestal also allows small children to easily reach the steering joystick. This single joystick – in contrast to two joysticks in real helicopter cock- pits – allows the execution of all the commands needed to exploit the various modes described in chapter 3.

The realisation of the whole installation required state-of-the-art computer technology. The core of it is formed by two high-end PCs with 3 GHz frequency and 3 Gigabyte RAM. These two computers are capable to calculate 7 million landscape polygons in real time. They export their output data to graphic cards with 256 MB storage capacity which then steer two daylight beamers with a resolution of 1024 x 768 pixels. From the technical view point, at present this interactive real-time terrain visualisation certainly belongs to the leading ones worldwide.

The geo-database behind this virtual flight consists mainly of a digital terrain model (DTM) of the actual National Park area with a horizontal resolution of 10 metres and a height accuracy of 1 metre. The true-colour im “unnatural” age data display a resolution of 1,25 metres. The region around the National Park proper is covered by a coarser resolution DTM draped by Landsat ETM imagery. This “frame” around the National Park prevents views from the helicopter towards “unnatural” horizons caused by the end of the virtual landscape model.

The visitors, however, do not at all notice all the high tech behind this installation. They just experience a very conven- ient, informative and entertaining possibility (cartography as “infotainment”) to learn about the habitat and the peculiarities of the Gesause National Park and to explore the landscape in a playful way.

5 FURTHER DEVELOPMENTS

There exist many ideas for a further development of the installation. Amongst others, both the text and the sound tracks of the video clips could be made multilingual. Furthermore, the surface texture of the landscape could be increased in areas with steep rock walls. This means that more or less horizontally taken photographs of shady vertical rock faces will be used to substitute the present texture which, due to the draping process shows unrealistic vertical streaks. This procedure has already been successfully tested at the Institute for Cartography of the Dresden University of Technol- ogy. Finally, various buildings could be modelled in a three-dimensional way, thus allowing the visitor to enter them and change the virtual flight into a virtual walk-through.

6 ACKNOWLEDGEMENTS

The described project could not have been realised without the very ambitious, efficient and effective cooperation of the following individuals: Klaus Habermann and André Kunert, Institute for Cartography of the Dresden University of Technology (pre-processing of geodata and PoI information), Matthias Gindele, Awaron Company, Wiesbaden and Karlsruhe (software development and beamer installation), and Bernd Hetze, Computing Centre of the Dresden Univer- sity of Technology (consulting in various software concerns). The author expresses his sincerest gratitude to all of them.

7 REFERENCES

Websites: www.solidterrainmodeling.com, accessed on 17 May 2005. www.awaron.com, accessed on 17 May 2005. www.verdandi.at, accessed on 17 May 2005.

BIOGRAPHY OF THE AUTHOR

Dr. Manfred F. Buchroithner is Full Professor of Cartography at the Institute for Cartography (IfC) of the Dresden Uni- versity of Technology (TUD). He holds degrees in both Geology & Paleontology (Graz, Austria) and Cartography and Remote Sensing (ITC, NL) and obtained his PhD in 1977. Out of his more than 250 articles more 60 have been pub-

lished in reviewed journals. Moreover, he has written three books and edited three volumes on remote sensing. For 4 years (1994-1997) Prof. Buchroithner served as Vice Chairman of EARSeL, the European Association of Remote Sens- ing Laboratories. In spring 1999 he was appointed Secretary General of EURO-STRIM, the European Association mandated to operationalise the European Doctorate in Space Technologies for Risk Management. For 7 years he was permanent lecturer at the U.N. Course "Remote Sensing for Educators" at the University of Stockholm. At the IfC he introduced short courses in Presentation Techniques and Project Management. In 1994 Prof. Buchroithner was awarded the honorary title of a "Euro-Ingenieur" for his postgraduate teaching activities and he was elected Full Member of the German Geodetic Commission at the Bavarian Academy of Sciences. In 2002 he was elected Member of the Academy Institution "Arbeitsgemeinschaft fuer vergleichende Hochgebirgsforschung" in Munich. He has been permanent re- viewer of the German Research Council (DFG) since 2000 and received several academic awards and honours, amongst them 3 "Best Map Awards" of the International Cartographic Association.