So what have we been up to last week?
29-02-2016 – Today we were kept to shore with torrential rain pouring on the island. Not that rain should in itself stop maritime archaeology but as we are using electronics and the water integrity of the vessel’s cabin is not perfect, we choose to err on the side of safety for the equipment. Taking advantage of another day on shore the team split up to achieve multiple objectives. Magnetometer data collected in previous days is being processed. Initially mag data was analysed which correlated to the expected wreck location of the Eidsvold. We were highly gratified to know that we were able to locate a known site.
Other work continued on translating Dutch archival information, preparing for proposed photogrammetry on the Emden site (should weather allow us access) and calibrating equipment for taking corrosion potential measurements tomorrow. A large amount of pot noodles and canned tuna continued to be consumed by the group!
Robert de Hoop & Graeme Henderson working on translating Dutch archival information.
Shinatria going through the calibration of equipment prior to commencing a corrosion survey of two local shipwrecks.
Computer Vision Photogrammetry
Recent advances in technology have made photogrammetry an easy and effective means of creating 3D models. The practice is now relatively commonplace on most archaeological excavations, terrestrial or underwater. Recognising the archaeological and interpretive value of photogrammetry team members have been practising collecting images and processing those images into 3D models to be better placed to rapidly document any site in the short time available during fieldwork.
Attached are some images of a Prahu Cadik located at Flying Fish Cove and an anchor found leaning outside the local pub. As you can see the anchor has a shackle (for chain) rather than a ring (for hemp rope). This is reported to have become common after the invention of the steam hammer in the 1830’s. The anchor may date from c 1840-1880 and is in the Admiralty pattern.
The 3D model of a Prahu Cadik which was located at Flying Fish Cove that we made.
A 3D model of an anchor found leaning outside the local pub.
We are now trying to make 3D models using GoPro footage from last year’s expedition.
01-03-2016 – Today was another rainy day, but we decided to go out on the water anyway. We surveyed the entire west side of the island and filled in some gaps on the south side. The surveying should now be done! With the weather clearing up we can hopefully start diving soon to check out the anomalies that we have found. Tomorrow morning the gathered data will be post processed and refined and in the afternoon, if weather allows it, we will dive on the Nissi Maru and the Eidsvold to measure the corrosion of the wrecks. This will give us an indication of the degradation/corrosion process around the island.
As Azmi Yon said: ‘It is like a tropical Baltic Sea’.
Everyone hard at work during the magnetometer survey.
Wrecksites around the island
In our previous blogs we also started to introduce other wrecks around Christmas Island. Beside looking for the Fortuyn other aims of this project are the training of students and the inventory of the seabed around the island. While doing our magnetometer research and continuing the historical research we came across other really interesting wreck sites. The two – non-Dutch- sites below -the Eidsvold and the Nissi Maru – will be dived upon in the days to come as part as a measurement to establish the rate of corrosion on the metal wrecks.
On 21 January 1942 the Norwegian vessel Eidsvold was loading phosphate in Flying Fish Cove, Christmas Island, when it was struck by a torpedo from the Japanese submarine I-159. The ship broke in two and was abandoned by her 31 crew. The vessel drifted and eventually sank off West White Beach. On the 6th of February, the crew were rescued by HMS Durban. They arrived at Batavia, Netherlands East Indies on the 20th of February. At that time, the attack of Japan on the Dutch colony has already began. The Dutch Indies will capitulate on the 9th of March that year.
The Eidsvold caught fire after it was attacked and is portrayed on a stamp from Christmas Island.
The location of the wreck is known and the team used this wreck to test the magnetometer. Taking the magnetometer over a known shipwreck site enables us to calibrate the instrument, and ensure ability to pick up ferrous material from an unknown shipwreck. It also helps to refine our ability to acquire data and interpret in the field. This allows great flexibility while working on the boat. The magnetic signature is clearly seen and the system is working extremely well. We will also measure the corrosion of this wreck using corrosion potential monitoring equipment later this week.
The result of taking the magnetometer over the Eidsvold.
Flying Fish Cove in 1929 from the cliff top. The pier is longer than it is now and during diving we found not only the Nissei Maru but also a lot of parts that must have belonged to the destroyed pier.
The same kind of corrosion measurements will be conducted on the Nissei Maru. This Japanese cargo ship of 338 tons was moored at the pier on the 17th of November 1942when it was torpedoed – as claimed – by the US submarine Searaven (SS-196). The island was occupied by Japanese forces at the time. The sinking of the Nissei Maru marks the end of Japanese attempts to export phosphate from the island. During the attack the pier was also damaged and a storm in 1951 did damage to the jetty even more and it was demolished soon after.
Robert de Hoop