The loss of Pennsylvania-class battleship the USS Arizona was the biggest blow of the attack on Pearl Harbor. On December 7, 1941, the ship was bombed in the surprise attack, causing a massive explosion that killed 1,177 of the 1,512 crewmen on board, and sinking the USS Arizona to the bottom of the harbour.
The ship was decommissioned on December 29 of the same year, and a memorial has been erected over the wreck to mark its resting place. Yet, despite several dive and salvage operations over the decades, the only existing record of the ship's design plans was a drawing made by hand.
Now, the US National Park Service has unveiled an extensive project undertaken last year in collaboration with creative software designer Autodesk: a comprehensive underwater scan of the vessel, inside and out.
"Technologically, this project is unprecedented," Autodesk strategic projects executive Pete Kelsey told CNET.
"Never before have so many different types of data been brought together to create an intelligent, high resolution, highly detailed model that can be used for so many different purposes. This project combined terrestrial laser scanning, SubSea LiDAR, SONAR and Autodesk's photogrammetry technology to capture the existing conditions of the ship and create a very accurate virtual model. Subsequently, the model can be used to generate 3D printed replicas of artifacts on the ship, such as a cooking pot, a Coke bottle, a catapult from the ship's stern, etc."
Teams from around the US contributed to the project. Autodesk provided photogrammetry; Sam O. Hirota, Inc. provided terrestrial laser scanning; Oceanic Imaging Consultants provided multibeam side scan SONAR (images produced by bouncing sound off solid objects); 3DatDepth provided subsea LiDAR (images produced by bouncing laser light off solid objects); and Shark Marine Technologies provided diver portable SONAR.
"These technologies had NEVER been combined before so we were pioneering a new way to bring all this information together," Kelsey said. "Interoperability was a significant challenge in the past, but with Autodesk ReCap technology we were able to import all of the different formats required."
The scan itself, which took place last year, only took 15 days in the field, compared to the 1983 scan, which required 90 days, and it only took three days of post processing compared to three years for the 1980s. The result is three-dimensional survey-grade photorealistic computer models. The team has even been able to reproduce some of the items found on the USS Arizona using 3D printing.
The team didn't find anything unexpected or unusual aboard the vessel, although it was in better condition than the team had thought it would be. They were also surprised to find corals growing on the ship, given that, to this day, it is still leaking oil at a rate of about 2.18 litres per day.
"However, seeing items that make a definite human connection like cups, saucers, plates in the galley, teak decking, the 3 x 14" guns of turret one up on the bow, ammunition on the deck, and steps that lead down an open hatch into the darkness were profoundly moving," Kelsey said. "Sailors and Marines lived, worked and died here."
And later this year, the public will be able to experience the results of the scans themselves -- both as 3D-printed objects and an interactive experience, which will allow users to explore the ship -- although an exact date and location for these resources is yet to be revealed.
"We have two primary objectives for this project: preservation and education. This is the first comprehensive survey of the memorial and the ship in 30 years; and the National Parks Service (NPS) hopes to gain understanding of what is changing on the ship because a steel ship in salt water is a finite resource. Understanding corrosion rates, coral growth and oil leakage from the ship are key points NPS wants to understand," Kelsey explained.
"On the education side, using 3D interactive computer models is a great way to reach a broad, new audience. Many visualisations and simulations of the ship can be made from these models including what the ship looked like when it was launched, when it was modernized, when it sank, etc."
Having proven that the technologies involved can be combined in this way, the teams are already starting to move ahead for the future.
"The workflows developed on the USS Arizona provide value for new advancements in cultural heritage preservation work. We are already in discussions with NPS, NOAA and others to do similar work on Midway Atoll, Palmyra Atoll, Peleliu and Chuuk (Truk Lagoon)," Kelsey said.