Abbadia Castle in 3D

The Abbadia Castle in the south west of France is one of the Unesco World Heritage sites the 3D-Icons project is producing an 3D model of. Loïc Espinasse explains in this story how this was done and where drones come into action.

Abbadia Castle overlooks the Bay of Biscay, near the Spain frontier with France. This château-observatory  in Hendaye is the property of the French Science Academy.  It was built at the end of the nineteen century by Viollet le Duc for Antoine d'Abbadie, ethnologist, geographer and scientist.

The castle overlooking Hendaye bay

This remarkable castle is the synthesis of Viollet le Duc architectural's theories.  The survey completed by Archéotransfert, a technological cell of Bordeaux 3 University was realized by 3D photogrammetry. This method of digitization needs a succession of different programs running directly on photographs. Each step of the photogrammetric process can be controlled and adjusted by means of parameters (affecting data correlation, refinement, robustness etc.) in order to produce the desired 3D data. 

The first step is the identification of different remarkable areas on each photograph. The algorithm search for possible similarity between those areas and identify the likeness from an image to another. From this correlation but also the camera and lens features, the second step is to use the metadata (named exif) present inside the digitals pictures. With this metadata the deduction of different positions and orientations of the cameras as they were at the moment of the shooting becomes possible. At the end of this step we get a first light reconstruction of the 3D model. The third step is to elaborate from different positions and orientations previously determined from the shooting, a dense reconstruction of a point cloud corresponding to the 3D model. 

An initial visit to the castle is needed to identify the different issues inherent with the site and to plan the shooting methodology. Photographs are made with a Nikon D800E camera and many different lens. The operator makes a first global shooting from every possible  points of view (ground, balcony, overhang etc). Two hundred photographs have been made for this mission. A first  point cloud is computed in order to notice the problematic areas for the second digitization mission. It evidently appears that the difficulties come from vegetation, roofs and multiples sculptures. In order to complete this first 3D model, two hundred aerials photographs are made with an EPC-D601 drone with an Eos 650D dslr. This new set of pictures also enables the possibility of generating the near topography of the castle. The last step of the digitization will be to survey the many different sculptures, in order to be insert them in the final 3D model of the Abbadia castle.

Abbadia Castle result