Applied to a virtual space, spatial zoom offers the ability to present increasingly detailed levels of information. Using the technique of zooming into multi-scaled hierarchical information, the finite space of the computer screen becomes an infinite space with infinite resolution. In a dynamic timeline with several levels of detail, the infinite zoom offers great possibilities for moving between levels while retaining context. Infinite zoom in a virtual space has been demonstrated in the Visible Language Workshop by Sabiston and later by Cooper, Small, and Ishizaki. Outside the Visible Language Workshop, Bederson and Hollan demonstrated a multi-scale hierarchical sketchpad in which moving from one area of information to another consists of zooming out to get an overview of the information, then zooming in to the new area of interest

external examples:

Where is the University of Umea located?
A zoomable world map produced using Xerox PARC Map Viewer, a World-Wide Web HTTP server that accepts requests for a World or USA map and returns an HTML document including an image of the requested map. Each map image is created on demand from a geographic database.

Terra-Vision (T-Vision)
ART+ COM
Harking back to Ray and Charles Eames film 'The Power of Ten', T-Vision is designed around seamless links between different levels of detail allows the continuous zooming from a global view down to recognisable features of only a few centimeters in size. Any kind of geographically-related data can be incorporated (e.g. biological, sociological, economic, etc.). The user rolls a beach-ball sized trackball, and a globe of the world presented on the screen, rolls correspondingly. The image is made up of a patchwork of satellite and aerial photos. The user can zoom from the macro-space view of the world down to individual streets and locations - in fact one can zoom into the Art+Com office, and look through a video camera pointing out the window, and see real-time video action.

Zoomable Interface Tools

Jonathan Meyer and Ken Perlin,
'Two Document Visualization Techniques for Zoomable Interfaces',
Meyer and Perlin developed two interactive document visualizations in Pad++, an environment for exploring zooming techniques for interfaces. The first is a page- based elliptical view that shows an entire document simultaneously and provides multiple navigation mechanisms that they used to develop a tutorial document. The second technique employs an inverted triangle view so that any size document can be presented in the same amount of space. Access is via zooming rather than panning.

Jazz
Jazz is a Java 2 toolkit that supports the development of 2D structured graphics programs in general, and Zoomable User Interfaces (ZUIs) in particular. Jazz makes it easy for Java programmers to build their own animated graphical applications with zooming, multiple cameras, layers, images, etc. You can even embed standard Swing GUI components in your Jazz application, combining traditional and custom graphics. ZUIs are an interface technique that present a huge canvas of information on a traditional computer display by letting the user smoothly zoom in to get more detailed information, and out for an overview. Information can be clustered to show what goes together, and users can intuitively grasp what information is accessible.

For more information, see;

Hua Guo, Jing Wu, Vivian Zhang, 'The Effect of Zooming Speed in a Zoomable User Interface'