Santo Antonio de Tanna Shipwreck Reconstruction Project
Daniel Adams, Andrew Woods, and Jeremy N. Green
The Santo Antonio de Tanna (1697) Shipwreck Reconstruction Project allows visitors to interactively visualise a shipwreck site completely uncovered and whole as it rested on the sea floor. The shipwreck site was discovered in the late 1960s, then excavated and surveyed over multiple seasons between 1977 and 1980. During the excavation, individual layers of the excavation were extensively photographed, and underwater observations were taken to establish control markers along the keelson, the port and starboard sides of the wreck. Photogrammetric 3D reconstruction techniques have been used to create digital 3D models of the Bow and the Stern sections and then control points were used to merge both halves of the hull together. The resultant model provides the most comprehensive understanding of the shipwreck site to date.
Model 4 - Showing first reconstruction of the complete uncovered site (model: Daniel Adams, Andrew Woods)
Controls
Use your left mouse button to rotate around the model, right mouse button to pan and scroll wheel to zoom into the finer details.
About the Project
Two Nikonos 15mm Lens Cameras were used during the survey of the Santo Antonio de Tanna to capture stereoscopic image pairs. Both cameras were setup on a stereo bar with half a meter separation and calibrated underwater. The stereo bar was then attached to a photo tower. The techniques used to record the complex hull structure of the Santo Antonio de Tanna has been published in the chapter: "Legacy Data in 3D: The Cape Andreas Survey (1969-1970) and Santo Antonio de Tanna Expeditions (1978-1979)". During the 2022 stage of the project which was funded by a grant from the George and Ann Bass Endowment for Nautical Archaeology Publications, the photographs were digitally scanned and underwent a contrast limited adaptive histogram equalization prior to any photogrammetry processing in order to better define the edges of objects and boost the contrast in the final textures. Approximately 80 digital control points were placed manually over 603 photographs to act as a guide to produce the 3D reconstruction seen above. These digital control points were primarily placed on the corners of ships planks, patterns and cracks in the wood and even seashells.
Previous Work - 2018
Model 2 - Showing reconstruction of bow section (model: Lachlan Shaw)
As a proof-of-concept project the previous work undertaken by Curtin HIVE intern Lachlan Shaw in 2018 had involved taking 570 images of the shipwreck (276 images captured in 1978 and 294 images captured in 1979) then processing it to create a 3D reconstruction of the Bow section. The work was funded under the ARC Linkage Grant Shipwrecks of the Roaring Forties: A Maritime Archaeological Reassessment of some of Australia's Earliest Shipwrecks (grant LP130100137). While the reconstruction of the Bow section below was mostly successful with the exception of some obvious errors, all attempts to reconstruct the Stern had failed using the traditional workflow. This was due to a number of reasons including lower quality scans, lower contrast without CLAHE, not so rigorous marker placement, but also not being able take advantage of the new image alignment strategies the HIVE team have developed over the last year. This work was published as a report on the WA Museum website: "The Photogrammetric Analysis of the Santo Antonio de Tanna"
Previous Work - 2021
Model 3 - Showing high altitude reconstruction of bow section (model: Jeremy Green)
One of the problems with the project was that the stereo photographs had been taken on a ridged tower. Using the tower ensured that the cameras were kept still and did not suffer from camera shake, which was particularly important in low light levels were slow shutter speeds were needed. However, an unexpected problem arose some 45 years later, when MetaShape had problems dealing with the grid frame and the legs of the tower, that appeared in the same place in each frame, whilst in the same frame it showed different hull structure. The program was thus confused as to what to do. It so happened that there was a series of photographs taken free-swimming without a tower at a relatively high altitude over the exposed bow structure. This enabled Jeremy Green, using the Contrast Limited Adaptive Histogram Equalization (CLAHE) program to create a model of the site, although because of the hight above the site the resolution was not particularly sharp. This sparked excitement for the upcoming stage of processing to be conducted at the Curtin HIVE using updated workflow.
Ongoing Work - Keelson Control Points with Port and Starboard Trilateration
Model 6 - Showing reconstruction using keelson control points (model: Daniel Adams, Andrew Woods)
Creating a three-dimensional model of the whole of the Santo Antonio de Tanna site was an immense challenge, because the site was never completely uncovered at one time. Each year different sections of the hull were uncovered and photographed. This meant that the model of each seasons had to be linked together to for a single model, however, in many cases the overlap in the models was small making the alignment difficult. Luckily, during the excavation in the 1970s measurements were made between control points that could be identified in the photographs enabling the models to be more accurately aligned. In addition, three-dimensional measurements had been made of the control points on the keelson that also added to the reliability of the overall model. So finally, we have a model of the whole site that has never been seen in reality. Problems still exist: there are lacunae in two areas along the keelson where the photography is deficient and extracting accurate measurement from the model, whilst excellent over small distances, is unsatisfactory over larger distances. It is hoped to address these problems in the future.
Further Information
Journal Article: Jeremy Green, Daniel Adams, Andrew Woods (2024) "The Use of Modern Technology to Obtain New Information from the 1970s' Excavation of the Portuguese Frigate Santo Antonio de Tanna, Wrecked in Mombasa in 1697", International Journal of Nautical Archaeology 53(1):53-73, Jan 2024.
Presentation: Daniel Adams, Andrew Woods, Jeremy Green (2022) "Photogrammetric 3D reconstruction of the Santo Antonio de Tanna shipwreck (1697) from legacy photography", Photogrammetry Network Seminar Series, May 2022, Curtin HIVE.