Distinguished Lecture Series: Global Terrestrial Relief Modeling: Challenges and Quality Issues

Until the eighteenth century, maps represented relief by symbolic shapes meaning "this is a mountain". Subsequently, advances in topography and then photogrammetry, stimulated by the needs of war and civil engineering, transformed the artistic work into a rigorous document. However, the maps of different countries differed in terms of specification (the choice of what the map should represent), scale and accuracy. As a result, the world map was a mosaic of sheets of heterogeneous quality. We had to wait for the advent of satellites to have a homogenous representation of the Earth's relief. The lecture will show how topographic techniques such as photogrammetry and radar interferometry, initially validated with airborne acquisitions, were implemented by satellite, first opportunistically and then with dedicated space missions. The particular case of forested regions such as the Amazon, where all the techniques are potentially degraded, will be considered. The question of quality will be addressed: the lecture will show the limits of the usual methods of validating 3D models, based on the statistical distance between the model and reality. Original approaches will be discussed, showing how geomorphological realism and hydrographic coherence can constrain the modelling of relief with invariant properties of the planet Earth.

Poster