Thérèse Ongena

Digital Representation of Historical Globes: Methods to Make 3D and Pseudo-3D Models of Sixteenth Century Mercator Globes

Abstract In this paper, the construction of digital representations of a terrestrial and celestial globe will be discussed. Virtual digital (3D) models play an important role in recent research and publications on cultural heritage. The globes discussed in this paper were made by Gerardus Mercator (1512–1594) in 1541 and 1551. Four techniques for the digital representation are discussed and analysed, all using high-resolution photographs of the globes. These photographs were taken under studio conditions in order to get equal lighting and to avoid unwanted light spots. These lighting conditions are important, since the globes have a highly reflective varnish covering. Processing these images using structure from motion, georeferencing of separate scenes and the combination of the photographs with terrestrial laser scanning data results in true 3D representations of the globes. Besides, pseudo-3D models of these globes were generated using dynamic imaging, which is an extensively used technique for visualisations over the Internet. The four techniques and the consequent results are compared on geometric and radiometric quality, with a special focus on their usefulness for distribution and visualisation during an exhibition in honour of the five hundredth birthday of Gerardus Mercator.

Ferraris, the Legend

Abstract At the end of the eighteenth century, a large-scale map of the Austrian Netherlands and the Prince-Bishopric of Liège was manufactured, covering more or less the current territory of Belgium. The work for this Carte de Cabinet was carried out by artillerists under the guidance of count Joseph de Ferraris, who was commissioned for the task by the Habsburg government. At the time that the map was designed, no modern legend was included. This paper tries to fill that gap by presenting a legend that was constructed more systematically than any of its predecessors. It is based on the structure of the legend of the Topographic Map of Belgium and the CORINE land cover map, making it an easy-to-use tool for modern researchers. The problems encountered during the development of the legend are described, and the link between the Carte de Cabinet and eighteenth-century French cartography as well as with cartographic manuals is also discussed.

The Evolution Of Soil Potentiality Concerning Salinity And Waterlogging Using Multitemporal Satellite Image Analysis In The Nw Part Of The Nile Delta.

This paper presents the first results of an attempt to model the soil salinity and waterlogging in the Baheira Province (Egypt). Fieldwork and multitemporal image classification were used to detect the areas subjected to salinity and waterlogging. Two sources of salinity could be distinguished: a lack of irrigation water and the infiltration of saline water from the drainage channels. Both phenomena could be simulated in a GIS, based upon the distances to the channel and the microtopography of the area.