Blurring Boundaries Between Real and Digital/Virtual Globes – Creating virtual globes from real ones and vice versa

Abstract

The recently opened Virtual Globes Museum publishes three dimensional virtual models of old globes on the Internet. The main purpose of the museum is to preserve these artifacts of old cartographers and at the same time to make them available for anyone who wants to study their content without the risk of making any harm to them. In this project, the authors established a bi-directional passageway between the world of virtual/digital and real globes. The developed technologies enable the easy creation of digital globes from handmade originals as well as the reverse process: the (re)creation of handmade globes from digital ones. The “heart” of the system is the Virtual Globes Museum, in which the globes are stored in an appropriate digital format. The images of the globe surface are archived in Platte-Carée, while those of the polar regions are archived in azimuthal equidistant maps. This “globe database” is fed from various input channels. The sources can be photo sets of globes or scanned images of printed segments transformed into a uniform image. This transforming process – especially when dealing with photographs – involves the problem of georeferencing, for which a special programme was developed. This programme calculates the projection parameters of a globe photo using control points marked on it. Another possible source is a newly compiled globe, when the globe map is created in the format that will be stored in the Museum, i.e. in Platte-Carée and azimuthal equidistant projection. This means that no further projection transformation is necessary. A current research project is trying to define the major guidelines of editing a globe map of this type. The possible output channels are the various digital visualizing forms of the globes: VRML models or KML globe layers for Google Earth, and a “down-to-earth” version: handmade globes based on the material stored in the museum. This latter procedure makes it possible to produce “facsimile” versions of old globes even without any original printed material by using a photo series of the globe. This paper intends to show a total cross-sectional view of globe digitizing by presenting examples of each procedure: digital globes made from photos or prints; globes designed to be virtual ones; and facsimile reproduction of the processed globes.