Krak des Chevaliers is one of the most important historical sites in Syria. Built during the Crusades in the 11th century, it dominates the route between Damascus and Homs from a rocky spur. Unfortunately, between 2012 and 2014, the fortified citadel was the site of fighting which caused serious damage to the structure.
Before any repairs can be undertaken, a thorough analysis of the damage is necessary. Together, the DGAM and Iconem have therefore carried out a series of surveys, both terrestrial and aerial. The latter involved the use of a drone, which overflew the building on 10 April 2016.
The photographs taken have enabled the construction of a highly accurate post-damage 3D model. This complements work begun in 2014 when Iconem and the DGAM reconstructed a pre-crisis model of the building, using a unique procedure which made it possible to retrospectively construct the model.
Krak des Chevaliers has long been the most visited citadel in the Near East. There are therefore many photographs of the site in existence, the majority taken before the crisis began. We created a robot – a small computer program capable of searching the Internet for images associated with the monument, then identifying and automatically storing them – and were thus able to gather thousands of royalty-free images of the citadel as it was before the war. By combining these images in a 3D reconstruction algorithm, we were able to extract a cloud of points in space in order to reconstruct the form and colour of the citadel. On the basis of this spatial data, it was possible to generate a 3D model representing almost a third of the building.
This pre-crisis model of the citadel is incomplete and not yet very accurate, as it was constructed only on the basis of a patchwork of separate images. However, it enables us to evaluate the damage by superimposing the post-crisis images over it. It is then possible to generate very accurate diagrams showing the damage the building has suffered, stone by stone and shell hole by shell hole.