This week we head to France on the D-DAY landing beaches, where Loïc Hussenet of Drones Imaging tells us how his team used old archives silver photos to reconstruct Boulogne-sur-Mer during the second world war.
Drones Imaging is a French society created in 2013 and situated near Paris at Maisons Laffitte. Headed by Loïc Hussenet, it is an office specializing in photogrammetry, 3D modeling, and geomatics. Experts in the analysis and processing of aerial images, Drones Imaging works worldwide to benefit civil & military UAV companies to provide them a high added-value geomatics service.
On June 15, 1944, nine days after the Allied landing in Normandy, 297 Royal Air Force bombers raided the port of Boulogne-sur-Mer, one of the seven fortresses of the Atlantic Wall. Sadly, their bombs missed their target and razed the city center. It will become the deadliest allied bombing of war.
Aerial photographs of the port of Boulogne-sur-Mer during the bombings where smoke from impacts is visible.
By navigating through the 3D model shown above built from old images taken in 1945, only 8 months after the bombing, the stigmata of the war are still visible on Boulogne-sur-Mer: sunken ships, bomb strikes, wharves and destroyed buildings are still visible everywhere on the scene. Also, you can see some recent traces of the allied landing. They are listed by clickable thumbnails on the 3D model.
To realize this historical model, Drones Imaging had to carry out a search of aerial images taken at that time to constitute a dataset whose quality and overlap criteria meet the standards of photogrammetry. This was the most complicated part because old photos are not always taken in ideal conditions of weather (especially during the war). Furthermore, silver images often deteriorate over time if they are not stored in good conditions (yellowing, scratches and stains). And if the quality is acceptable, it is still necessary that the overlap had to be normalized. This is why it is very hard to build 3D renderings from old silver photos.
Fortunately, on March 22, 1945 (8 months after the bombing of Boulogne-sur-Mer), the French army carried out an aerial reconnaissance mission in exceptional weather conditions and made a set of aerial images of the port.
“ National Geographic Institute (IGN), in charge of aerial imagery archives for the French cadastre, provided us with scanned images of this aerial reconnaissance. If we were surprised by the high recovery rate between each shot and the excellent quality of these images, we still had to plan specific processing to optimize blurred areas, erase the blemishes, scratches and harmonize the brightness / contrast. But at this stage, we knew that it was possible to model the port of Boulogne-sur-Mer during the world war 2.”
~ Loïc Hussenet.
Perfectly suited for extreme work, we used PhotoScan software to model the port and a big part of the city of Boulogne-sur-Mer. Of course, the quality of the 3D model is limited but it is already large enough for a presentation in a museum or an immersion in the past.
At a time when 3D replaces the 2D, this procedure is promising because it makes it possible to give life to old photos and this allows illustration of historical events through 3D, as it was at the time. Given these encouraging results, Drones Imaging is now in touch with the historical military service to propose this very special 3D modeling service.