POTENTIAL OF VIRTUAL 3D-FACSIMILES EXEMPLIFIED BY THE EARTH GLOBE OF GERARD MERCATOR (1541)

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1 POTENTIAL OF VIRTUAL 3D-FACSIMILES EXEMPLIFIED BY THE EARTH GLOBE OF GERARD MERCATOR (1541) Florian Hruby, Irmgard Plank, Andreas Riedl Project associate, Project associate, Associate Professor, Department of Geography and Regional Research, Cartography and Geoinformation, University of Vienna 1) ABSTRACT The aim of this paper is to review, survey and prospect possible approaches dealing with representations and reproductions of historical globes. We will go along the chronological development of methods and data formats from the analogue beginnings to the digital state of the art. The second part of the paper deals with the results gained from research work done on the basis of a 3D-facsimile of Gerhard Mercator s ( ) earth globe. This example shall illustrate the concrete functional and methodical requirements to generate a cartographic expression that allows close investigation not only by scientists, but also by the general public. To conclude, we will give insight in the potential of virtual globes exemplified by new discoveries that have been made under use of the digital Mercator globe. 2) POSSIBLE APPROACHES DEALING WITH REPRESENTATIONS AND REPRODUCTIONS OF HISTORICAL GLOBES 2.1) Review and Survey Approaches to representations and reproductions of historical globes can be discussed with different criteria. The scope of this paper is to exemplify techniques used to map the globes' surface, along with its follow up representation, as well as the objective of this procedure. Solely analogue instrumentation was used by Kohler in 1975/76 [KOH-78]. The apparatus he constructed allowed to assemble a globe and a camera in a way to take photos systematically. Applying this method he photographed a globe of W. J. Blaeu (1599) and a globe of G. Valck (1700). Each photo mapped 20 x 20 so that 162 pictures were necessary to cover one globe. Finally the photos were agglutinated lamellar to create 20 wide gores. The aim was to ease comparative research work without requiring direct access to the original globes, also should the images be part of a globographic database. In 1978 the problem was handled more complex and more exact by Kraus and Vozikis [KRA-78]. They processed images photogrammetrically by using the digitally controlled differential rectification. This technique allows to generate an output-image with the geometrical quality of a cylinder, that is then unrolled in the plane. This photogrammetrical approach has been enhanced and supplemented with methods of digital image processing [KAG- 92], [SAC-99]. In practice, their first step was to focus on the exact representation of a globe in the plane, with the aim of its restoration and documentation. In theory the reversed procedure was known and emphasized from the beginning, i.e. the possibility of (re-)producing a globe based on this rectified images [KRA-78]. The realization of this theoretical step had to wait until 1992, when the 500th anniversary of the Behaim globe gave occasion to various studies on this object. Then such reproduction was not limited to an analogue result any more as proven by Hans Klimpfinger's digital Behaim globe [KLI-93].

2 Klimpfinger's digital Behaim globe was one of the first exponents of a virtual hyperglobe, which can be seen as an early category of digital globes, marking the beginning of a still open-ended development. Hyperglobes show a digital representation of a virtual globe in virtual space [RIE-00]. However, the digital representation of ancient globes has only marginally drawn the attention of scientists. Therefore the number of published digital facsimiles is small up to the present. To mention is a virtual replica of the Karl-Theodor globe of the Heidelberg University Library made within the scope of the restoration of the original globe of 1751 [JÄG-04]. A common characteristic with both afore mentioned globes is the Virtual Reality Markup Language (VRML) model to create a sphere. Apart from this technical aspect both objects do not seem to have been the exclusive focus of a research project. The globes were realized as virtual facsimiles but the criteria to publicize an ancient cartographic product are just partly met, and probable have not been a main ambition. Conforming to those cartographic criteria is a facsimile, which allows the user to extract the correct perception and appropriate cognition of reality (cp. [HAK-02]), which is in this case a historical one. To assure this a digital reproduction is needed, that offers special possibilities concerning functionality and interactivity, which had to be realized according to the mentioned maxim in a consequential way. With this objective a digital facsimilation of the earth globe made by Gerhard Mercator in 1541 is being generated by the cooperation-project between the University of Vienna, Department of Geography and Regional Research and the Austrian National Library. One outcome should be the presentation of the facsimile in the Globe Museum - the only one of its kind in the world - which is part of the Austrian National Library. The implementation of a virtual hyperglobe is one of the main topics. For explanations concerning functionality and interactivity see part 4. In the following the process from the original globe to the digital facsimile will be discussed. Again the original globe was photographed at first. However, the digitalization of the globe's surface took place in the very first step, by using a digital camera. The whole globe was photographed in 432 single shots with high resolution (2560x1920 pixels; TIF), each of them showing a sector of 10 latitude x 15 longitude. Afterwards each photo with its own coordinate system was transformed to a reference system. This was done via ERDAS Imagine to obtain an equidistant cylindrical projection (plate carrée). Finally the photos were merged to one single overlay and corrected radiometrically as well. This overlay had to be adjusted to 8192x4096 pixels in order to meet a certain quality and performance level. The digital facsimile was build then with Macromedia s Director as Shockwave3d application. Figure 1: Rectification of the original globe`s photos (above) and the scanned reprints (below) with the resulting overlay exemplified by the northwestern part of Spain.

3 With this procedure the digital representation of the original globe was completed. Yet the Austrian National Library submitted another two-dimensional source of the earth globe of Mercator. These are printed gores that have been reedited by the Royal Library of Belgium in The primarily intention to add this uncolored reprints was to improve the readability of the original, that showed signs of wear here and there. For this reason the prints have been scanned with 600dpi and afterwards processed analogue to the algorithm described above (Fig. 1). Result was another image-file to provide a basis for a second overlay. But once overlaid it turned out, that the two sources showed previously unknown differences in a few details. Their explanation and integration to the history of the Mercator globe is still outstanding, but another application area of virtual globes is suggested here. 2.2) Prospects As we have stated, virtual globes are decisive for digital facsimilations of ancient globes up to now. Meanwhile the development of new forms of digital globes is going on. Tactile hyperglobes are already transferred out of virtual into real space, where they get realized as a projection on a material sphere. Hologlobes finally are visualized on a virtual body in real space [RIE-00]. Tactile hyperglobes and hologlobes are not in a matured phase yet, but their potential for 3D-facsimiles is conceivable on principle. But recent technical development is not only concerning the representation of historical globes, but also the acquisition of data of a globe's surface. As yet the 3D-original has always been the source to create a 2D-map, which serves as an overlay for the final 3D-facsimile. This intermediate step could loose its current necessity using 3D-scanners, whose direct outputs are x-, y-, and z- coordinates. The term "3D-scanner" stands for different systems, serving varying application areas. Testing their limits still needs a lot of practical experience. Anyhow there are already projects coming up with positive results and opinions whereby such equipment can improve or completely replace close-range photogrammetry [MAR-03]. On the other hand we have inexact and incomparable manufacturers' instructions as well as reviews of abortive projects [BÖH-04]. The concrete potential of 3D-scanners to digitize an analogue physical globe's surface is tested by Tomberger [TOM- 05]. According to him triangulation type laser scanners are most suitable for this kind of objects. But also these systems generate inaccurate reproductions concerning the geometry and texture of the surface, which means a grave shortcoming for the purpose of facsimilations. Nevertheless overcoming these obstacles can be expected with the next generations of 3D-scanners. Besides showing the surface it can make sense to integrate the inner structure of the globe to its representation, especially in the case of 3D-demonstrations. Promising methods are therefore the use of X-rays or computer tomographies. Results referring to this can also be found in Tomberger [TOM-05]. 3) SUITABLE FORMATS FOR GENERATING DIGITAL FACSIMILES IN 3D-ENVIRONMENTS First of all the term "suitable" as a data format's attribute needs to be defined, because within the whole process of cartographic communication many data formats can be suitable for different aspects (e.g. GIS- or database formats). In this case it is about generating facsimiles, in the strict sense digital 3D-facsimiles. Therefore just those data formats will be considered, which will meet these criteria. Furthermore to address the general public the format should allow 3D-visualizations via Internet. Among numerous existing formats just a few are of importance. Commonly used formats are VRML (vector-based) and QTVR (rasterbased), whereof raster-based Virtual Reality (VR) applications are for the time being more popular and more accepted. As they actually reproduce objects in a pseudo-3d space, raster-based formats represent an own category for other purposes wherefore they will be excluded in this case. Most suitable for obtaining a 3D-facsimile as a 3D-object are currently the vector formats X3D and w3d (Shockwave 3D) (cp. [RIE-02]). These are also the formats used to create the 3D-facsimiles named above. Concluding we can state that up to the present an optimal 3D-standard has not been established.

4 4) REQUIRED FUNCTIONS AND INTERACTIVITY FOR INVESTIGATING DIGITAL 3D- FACSIMILES For investigating digital 3D-facsimiles various functions are necessary. The user or in this case the visitor of the National Globe Museum in Vienna, Austria, needs to interact with the 3D-facsimile. Fuhrmann et al. [FUH-00b] state, that 3D-interaction can be described as a consequence of target-oriented actions that take place in a three-dimensional space. Those actions are effected by the interdependency of men and machines. In terms of the digital 3D-facsimile it can be stated that the main advantage of a digital globe is interactivity. The user communicates actively with the application and therefore gathers information more quickly. The following functions can be differentiated: Navigation and orientation (spatial, temporal and thematic) Direct manipulation of the appearance concerning scale and thematic parameters Information retrieval and integration These three cartographic interaction categories determine the functions which shall be implemented in the 3D-facsimile of Mercator s globe. As an interactive system developed for use in a public museum the main task is to provide visitors with functions for navigating on the globe facsimile. By that one has to consider that according to Frank Thissen [THI- 00] the navigation and its elements should fulfill various attributes: Navigation suits the users aims, anticipation and behavior. Navigation happens instinctively. Navigation is consistent. There are various possibilities how to navigate. Therefore it is necessary to offer the user the possibility of navigating in spatial, temporal and thematic dimensions. For that, the importance of additional control elements for the interpretation of cartographic multimedia applications is pointed out by Suzette Miller [MIL-99]. Such control elements or navigational functions should use appropriate metaphors for better understanding. Interactive metaphors convey the software concept to the users without the need of understanding the system model behind. Such metaphors are task- and user-specifically created. The metaphor selection of everyday life depends on key features for the chosen tasks (compare Fuhrmann and MacEachren [FUH-00a]). 4.1) Virtual Facsimile of the Mercator Earth Globe for the National Globe Museum, Vienna, Austria Especially for the use of interactive systems in museums, Robert J. Semper [SEM-98] created distinctive features to differentiate between the various possible applications, whereby the typological classification can be as follows: Passive Presentation Guided Experience Interactive Browsing Systems Direct Creation (Interaction) The 3D-facsimile of the Mercator earth globe belongs to the type Interactive Browsing Systems. Such systems allow inquiring databases that are based upon texts, charts, sounds and animations. According to the demands pointed out at the beginning of this chapter, the following features have been implemented: As any 3D-object a digital 3D-facsimile requires navigation and information tools for exploring and gathering additional information. That includes rotation as well as zoom, interactive buttons and extra thematic overlays. Concerning orientation and navigation it can be stated that the implemented overview globe allows the visitor to discover the area on the main globe he or she looks at. A zoomed area is shown by using a red rectangle. The navigation is to be kept simple for not causing confusion. Therefore, like an analogue globe, the digital 3D-facsimile is allowed to rotate up or down until reaching the poles or horizontally around 360 degrees. This is possible by using either the cursor with mouse-movements or by hand via touch screen. The programming behind the 3D-model allows to rotate the digital globe by moving it in correlative distance to the cursor-movement on the screen in the indicated direction. In some globe applications examined by the authors one can find so called overflight rotation or movements (which means that the globe moves in the opposite direction as the cursor movement indicates). In our tests such movements were confusing and are therefore to obviate.

5 Indicated Rotation Overflight Rotation Figure 2: Indicated and Overflight Rotation Regarding direct manipulation of the appearance concerning scale and thematic parameters it is necessary to provide the user with zoom in and zoom out buttons as well as a zoom level indicator. The thematic overlays provide the amount of information in accordance to the zoom level chosen. For example the overlay showing current cities in Europe offers maximum details only at the highest zoom level. Visitors can add various thematic overlays by simple interactive buttons but can not vary thematic parameters of the current overlays. That was considered unnecessary for an application in a museum visited by cartographic laypersons. As far as information retrieval or integration is concerned, it is implemented by providing written information on the various overlays. These information buttons according to either the Mercator overlay or the thematic overlays are connected to pop up windows. The user can close them by clicking a button and return to the main application. Direct integration of data is not appropriate in this case. Now then, cartographic interaction can be acquired by connecting up to date and historical content through two different globe models. Each of them can be rotated separately by using the active model function programmed on the two models. This facilitates historical comparison. Therefore Mercator s coastlines can be compared with recent coastlines, historical cities locations with their actual position in the global context and known rivers of the past with selected streams in the present. More information on the thematic overlays is provided in the following chapters 4.2) Introducing the interactive 3Dfacsimile and 4.3) Discoveries. 4.2) Introducing the interactive 3D-facsimile Figure 3 shows all functionalities of the 3D-facsimile. Interactive buttons allow switching between various thematic overlays, which include the digital form of the printed Mercator globe segments. Navigation tools are presented as well as the active model functionality. First one can see the facsimile of the earth-globe with its view as it is given on the original globe. By activating the globe segments the additional contours as originally printed appear to improve the readability of the worn out original image. Actual themes as graticule, coastlines, streams and cities can be added to enable comparisons between historical and up to date facts. To achieve that, one of the active models can be disabled to be moveable. Then one can move the recent coastlines of Africa, for example, alongside the historical African coast to compare how this part of the world was seen in the 16 th century and how accurate or not cartographers at that time worked.

6 Figure 3: Screenshot 3D-facsimile of the Mercator earth globe 4.3) Discoveries Whilst exploring the virtual globe and comparing it with the printed globe segments which show the true historical contents of the globe, various detections were made. Mag. Jan Mokre, Director of the Vienna Globe Museum, explains that most of the globes were colored after being bought. Therefore after maybe years of storage and occasional damage during that time and due to the fact that some artists (who were not trained cartographers) could not paint properly the image was altered. Or maybe the globes were already timeworn so that the real contours could not be viewed exactly and therefore restoration trials seem also to have left errors. That might explain why the River Nile ends on mainland and Cyprus is not an island (see Figure 4). In fact, the River Nile is labeled Aegyptos as for its name in former times. By exploring the historical cities one can also find that many of them are labeled either in their Latin names or in other names used in the 16 th century. Many of the European coastlines were also painted incorrectly. Spain, France, Great Britain and Denmark show different extents than printed on the historic globe segments. The same can be told about various islands whose contours were not properly filled with color. The Sunda Islands for example are merged to fewer but larger islands. Some oceans labeling varies in comparison to the facsimile with the printed segments. There it looks like the restorers had problems in guessing/writing the correct letters.

7 Figure 4: Screenshots of the Eastern Mediterranean: Cyprus and Nile Delta as shown on the Mercator earth globe (left picture) and as shown on the printed globe segments (right picture) with recent coastlines (in white) The investigation and comparison of the earth globe with its original printed segments is just at the beginning. It will take a long time to find all the differences between the facsimile and the printed segments but the discoveries made so far are more than worth the effort. REFERENCES [BÖH-04] [DRA-99] [EAC-00] [FUH-00a] [FUH-00b] [HAK-02] [JÄH-04] [KAG-92] BÖHLER, Wolfgang, MARBS, Andreas: Vergleichende Untersuchung zur Genauigkeit und Auflösung verschiedener Scanner. - In: Luhmann, Th., Photogrammetrie, Laserscanning, Optische 3D-Messtechnik. Beiträge der Oldenburger 3D-Tage - Heidelberg, pp A DRANSCH, Doris (1999): Theoretical Issues in Multimedia Cartography. In: CARTWRIGHT, W., PETERSON, M.P., GARTNER, G. (Hrsg.): Multimedia Cartography. Springer-Verlag Berlin Heidelberg pp MACEACHREN, Alan M., KRAAK, Menno-Jan (2000): Research Challenges in Geovisualization. In: Kartographische Nachrichten 4/2001. Kirschbaum Verlag Bonn. pp FUHRMANN, Sven, MACEACHREN, Alan M.: Navigation in desktop-basierten geo-virtuellen Welten. In: Kartographische Nachrichten 3/2001. Kirschbaum Verlag Bonn. pp FUHRMANN, Sven et al.(2000): Anforderungen an 3D-Interaktionen in geo-virtuellen Visualisierungsumgebungen. In: Kartographische Nachrichten 4/2001. Kirschbaum Verlag Bonn. pp HAKE, Günter, GRÜNREICH, Dietmar, MENG, Liqiu: Kartographie. 8. Auflage. de Gruyter, Berlin, New York, pp. JÄGER, Willi, KRÖMKER, Susanne: Map Projection versus Image Processing the Role of Mathematics in the Restoration Process. In: JÄGER, Willi, KRÖMKER, Susanne, WOLGAST, Eike (ed.): Der Heidelberger Karl-Theodor-Globus von 1751 bis Springer-Verlag Berlin, Heidelberg, New York, 2004, pp KAGER, Helmut, KRAUS, Karl, STEINNOCHER, Klaus: Photogrammetrie und digitale Bildverarbeitung angewandt auf den Behaim-Globus. In: Zeitschrift für Photogrammetrie und Fernerkundung, 5/92. Karlsruhe, 1992, pp

8 [KLI-93] [KOH-78] KLIMPFINGER, Hans: Visualisierung von Oberflächen und Oberflächenveränderungen mit dem Softwarepaket IDL (Interactive Date Language). Unpublished Master's thesis at the Vienna University of Technolgy, 1993, 56 pp. KOHLER, Alfred: Die Verebnung von Globen eine neue Methode zur Lösung eines alten Problems. In: Globe Studies, Vienna, 1978, pp [KRA-78] KRAUS, Karl, VOZIKIS, Evangelos: Die Verebnung von Globen mit Hilfe der Differentialumbildung. In: Globe Studies, Vienna, 1978, pp [MAR-03] [MIL-99] [PET-99] [RIE-00] MARBS, Andreas: Erfahrungen mit 3D Scanning am i3mainz - 2. Oldenburger 3D-Tage - Oldenburg, ( ) MILLER, Suzette (1999): Design of Multimedia Mapping Products. In: CARTWRIGHT, W., PETERSON, M.P., GARTNER, G. (Hrsg.): Multimedia Cartography. Springer-Verlag Berlin Heidelberg pp PETERSON, Michael P. (1999): Elements of Multimedia Cartography. In: CARTWRIGHT, W., PETERSON, M.P., GARTNER, G. (Hrsg.): Multimedia Cartography. Springer-Verlag Berlin Heidelberg pp RIEDL, Andreas: Virtuelle Globen in der Geovisualisierung. Untersuchungen zum Einsatz von Multimediatechniken in der Geokommunikation (mit einem Nachwort Globenforschung in Österreich von I. KRETSCHMER). In: Wiener Schriften zur Geographie und Kartographie, vol. 13. Vienna, 2000, 158 pp. [RIE-02] RIEDL, Andreas, KATZLBERGER, Gernot, TOMBERGER, Harald: Entwicklungs-/Modellierumgebungen für Web-basierte Geo-Virtual Reality Applikationen eine Gegenüberstellung. In: M.Schrenk (ed.): CORP2002-Geomultimedia02: Beiträge zum 7. Symposion zur Rolle der Informationstechnologie in der und für die Raumplanung, vol. 2. Vienna, 2002, pp [RIE- 02] [RIE-05] [SAC-99] [SHN-98] [TOM-05] RIEDL, Andreas: Web3D: Entwicklung, Standards, Formate. In: Kartographische Nachrichten 5/2002. Kirschbaum Verlag Bonn. pp RIEDL Andreas : Digital Globes - from Virtual to Real In: Proceedings, 22. ICA Cartographic Conference, A Coruña, Spain, SACHER, Gisbert, HEMMLEB, Matthias, SCHEER, Annette: Mapping of Globe Surfaces into a Plane with Digital Photogrammetric Methods. In: Globe Studies, 47/48. Vienna, 1999, pp Shneiderman,Ben (1998): Designing the user interface. Strategies for effective human-computer interaction. Reading, Addison-Wesley. 640 pp. TOMBERGER, Harald: Der Digitalglobus als Werkzeug für die Globographie. Unpublished Master's thesis at the University of Vienna. Vienna, 2005.

9 Authors Florian Hruby Florian Hruby (Hollabrunn, Lower Austria 1978) has been a student at the University of Vienna, Department of Geography and Regional Research, Cartography and Geoinformation since He has been teaching assistant on Geographic Information Systems since From 2004 on he has been project associate in the MUGL-project (Multimedia Globe Museum). He has acquired some international experience by participating during a three-month assistantship in the SICATUR-project (Sistema Cartográfico Turístico de la Costa de Jalisco) at the Department of Geography in the University of Guadalajara, Mexico. Currently he is elaborating his diploma thesis concerning the topics of cartosemiotics and three-dimensional landscape modeling. Irmgard Plank Born in Lower Austria in 1976, Irmgard Maria Plank attended various schools for basic education as well as business and tourism. After five years working as hotel receptionist and management assistant she decided to reorganize and started studying at the University of Vienna, Institute for Geography and Regional Planning, Cartography and Geoinformation, in autumn Since 2001 she holds various tutorials in computer applications, GIS and Visualization, data modeling with GIS. Now, besides writing her diploma, she is working on the MUGL project, for the Austrian National Library. This project aims in creating multimedia applications containing historical and current data on virtual globes as well as further information for being presented in the new Globe Museum in Vienna, Austria. Andreas Riedl Assistant professor Dr. Andreas Riedl, born 1965, studied cartography at the University of Vienna, Department of Geography, between 1987 and Subsequently, he was employed as a research assistant in the cartographic office of the department, and he worked freelance in the field of geoinformation and geovisualization. In addition to that, he carried out research work at the Simon Fraser University in Vancouver, Canada and he participated in the development and programming of courses for multimedia-cbt ("Computer Based Training"), topics GIS and remote sensing, at the ITC (Enschede, Netherlands). Since 1997, he has been assistant professor at the University of Vienna, Department of Geography and Regional Sciences. He finished his dissertation, which has been published 2000 as a book entitled Virtual globes in geovisualization - Studies in the use of multimedia techniques in geocommunication, after more than two years research work. His scientific priorities are applied geoinformation (GI) and the integration of multimedia techniques (3D-visualization, web-mapping, virtual worlds) into geocommunication. He is board member of the Austrian Geographic Society, responsible for inner affairs of the Austrian Cartographic Commission and corresponding member of the ICA Commission on Visualization and Virtual Environments. (