In the late fifties Waldo Tobler developed MIMO (Map In/Map Out). The three basic elements, map input, map manipulation and map output, still form the basis of today’s geo-information tools. The scientific evolution from MIMO via geo-information systems to Geographic Information Science (GIS) reflects fifty years of changing thinking. Today’s technology enables digital creation of three-dimensional (3D) look-alike representations of the real world. Still a representation, a descriptive model but, as Fisher and Unwin remarked, “Virtual reality is the ability of the user of a constructed view of a limited digitally-encoded information domain to change their view in three dimensions, causing update of the view presented to any viewer, especially the user”. ‘Their’ and ‘any’ refer here to sharing the view; the view is 3D and no longer a 2D cartographic projection. Fisher and Unwin’s publication and those that succeeded it show how fresh and innovative is research on Virtual Reality and geo-visualisation; up pops the metaphor of a digital peep-box.

Peep-box
As children many of us rose to the challenge of transforming a shoebox into a peep-box. We decorated the faces inside with pictures cut out of glossy magazines or painted them, glued cardboard objects onto the floor of the shoebox and hung them from the ceiling on bits of string. The faces formed boundaries and the light coming through one or more holes, often covered with coloured cellophane to create a mysterious atmosphere, illuminated the scene. Looking through the peephole gave the feeling of being in an imaginary world. The peep-box metaphor helps explain the transition from digital map to geo-virtual reality, referring to its three main components. Firstly, the 3D scene represents the peep-box boundary by a given extent of a 3D geo-referenced scene. Secondly, data forms the building blocks for constructing a 3D scene mostly founded on (2D) georeferenced data. Several digitally defined objects consisting of simple or more complex geometry in combination with digital pictures (bit-maps) may be placed on this base; for example, the ‘faces’ could be ‘mapped’ by digital
photos. Some objects represent atmospheric lights: fog, dusk, clear blue skies, night, so standing in for cellophane. And a complex 3D scene finally becomes a good example of data fusion. However, all the objects in a 3D scene are initially static in nature. Third, the interface between user and 3D scene represents the peephole, and the 3D scene may be experienced from different viewpoints and angles, graphic and geometricproperties such as level of detail, and items of interaction.

Change to GeoCom
The metaphor leaves aside state-of-the-art items of technology in interfacing, data fusion, data representation, simulation and feedback, all of which rely substantially on distributed computing. For this the metaphor could be extended to express new user perspectives. Interfacing refers to user interaction with a 3D scene. The viewer provides two ways of interaction:

• in the 3D scene, giving the user the impression of being in the virtual world
  
• off the 3D scene: with the help of viewer settings the user defines how the 3D scene will be experienced and analysed.

• Buhmann, E., Paar, P., Bishop, I., Lange, E. (eds), 2005, Trends in Real-Time Landscape Visualization and Participation, Wichmann.
  
• Dykes, J., MacEachren, A.M., Kraak, M.J., 2005, Exploring Geovisualization, Elsevier, 2005 (on behalf of the International Cartographic Association (ICA)).
  
• Fisher, P., Unwin, D., 2002, Virtual Reality in Geography Systems, Taylor & Francis.
  
• Peng, Z., Tsou, M., 2003, Internet GIS. Distributed Geographic Information Services for the internet and wireless Networks, John Wiley & Sons.

Aldo Bergsma is technical GIS specialist at the Laboratory of Geo-Information Science and Remote Sensing at Wageningen University. His main research and teaching interests are in the field of applied GIS and Location Based Services.