surfaces, where the land is colourcoded so that higher densities are darker. In design terms they are really quite conventional cartographic maps, using a geographic framework of continental outlines to show univariate data. This type of world map is familiar to most people and can be easily produced using GIS software, and succinctly summarises a large volume of data in an intuitive manner. The final way that maps have been used by academics and commercial research teams is a means by which to display measurements that quantify the extent and use of Internet infrastructure so as to gain a better understanding of its distribution, diffusion and utilisation. [15] In an ‹arc map› of Internet traffic flows between fifty nations, from February 1993, the colour, thickness and height of the arcs are used to encode the traffic statistics for particular inter-country routes.[16] In the SeeNet3D application in which the image was generated, the user had considerable interactive control able, for example, to vary the arc height, scaling and translucency. The map could also be rotated and scaled, so that the user can view it from any angle. The map shows that there was significant traffic, in the early 1990s, between

three areas of the world, North America to Europe, Europe and Australiasia, and Australiasia and North America, with most traffic crossing the Atlantic. The map does not show all traffic, however, because it is limited to just fifty countries. As such, it portrays a selected image, one that is dominated by developed countries that were the principle nations connected to the Internet in 1993. The final example is the Internet Mapping Project being undertaken by Hal Burch and Bill Cheswick at Lumeta Corporation.[17] Their project maps the topology of thousands of interconnected Internet networks to provide perhaps the best currently available large-scale overview of the core of the Internet in a single snapshot. They map the Internet in an abstract space (i.e. using a process of spatialisation), thus disregarding the actual location of nodes in physical space. Data is gathered by using the Internet to measure itself on a daily basis, surveying the routes to a large number of end-points (usually Web servers) from their base in New Jersey, USA. The resulting spatialisation maps how hundreds of networks connect together to form the core of the Internet. In the example shown, links have been colour-coded