Combination of Terrestrial Recording Techniques for 3D Object Modelling regarding topographic constraints. Example of the Castle of Haut-Andlau, Alsace, France.

Perched on a granite rock, the Castle of Haut-Andlau is surrounded by forests and ditches which make its access difficult. Only after the first crumbling, the Lord of Andlau worried about its durability and conservation. Since only poor documentation about the castle exists, a complete surveying of the castle was demanded. The problematic became a true challenge, regarding the constraints implied on the one hand by the steep and abrupt terrain surrounding the castle and on the other hand by the dense and broadening vegetation in the immediate vicinity of the castle. In this context, two universities shared their experiences and instruments: the Institute of Photogrammetry and Remote Sensing (Universität Karlsruhe (TH), Germany) and the MAP-PAGE team (INSA de Strasbourg, France). It became rapidly obvious that a unique technique would not overcome the vegetation and relief obstacles. That's why several recording techniques have been investigated. A quality assessment lead to the analysis of the models derived from each technique and to a crucial experience for further campaigns. Therefore, recommendations for an efficient acquisition planning and data processing are gathered. These solutions will help the castle owner to establish the framework of restoration tasks, by showing the destroyed historical structures. Moreover, they will help us to convince the department council to extend these first conclusions to the documentation of numerous other castles of the same type and therefore to insure the future of the Alsatian medieval patrimony