Tag Archives: underwater

The Rooswijk 1740, an update

Today we give you a short update about the work that the joint Dutch-English team of archaeologists is doing on the Rooswijk shipwreck.

The Rooswijk was a Dutch East Indian (VOC) ship that sank on an outbound journey on the Goodwin Sands in the UK, one day after it left the Texel Roads. All hands were lost and the wreck is now lying at approximately 24 metres depth.

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The dive team that worked on the site in 2005 gathered a  lot of information on site and lifted – amongst others – silver and gold coins and silver ingots. The information gathered at that time has not been published yet, but also lacks sufficient context with the ship construction.

Historic England designated the wreck site in 2007 under the Protection of Wrecks Act 1973 (https://historicengland.org.uk/listing/what-is-designation/protected-wreck-sites/wreck/rooswijk).

Current information has shown that the site is under threat of erosion of the seabed. The Goodwin Sands is a very dynamic area with huge sandbanks moving constantly.  This also became evident by comparing sonar recordings of 2015 and July 2016.

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The team wants to investigate how much the site is threatened, but also where this extra information to connect objects to the wreck can be found. The current research could lead to an extensive excavation which may possibly be conducted in the next coming years.

Before such an undertaking can be executed more information should be gathered about the condition of wood, iron and other material, about the best place to start an excavation and how this research could be best executed.

The team consists of archaeologists from the Cultural Heritage Agency (RCE), Historic England, the former dive team working on the site in 2005, Wessex Archaeology (the contractor for Historic England) and MSDS Marine, the current dive contractor.  We are working on the dive support vessel Predator from Essex.

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We are now 5 days on our way. The sun is shining constantly and the first days the weather was very good on the site. The visibility as well (approx. 2 metres). However, wind has picked up from the wrong direction now and we have lost a few tides on Thursday and Friday.

The site has however been found, canons have been identified and we are now working on mapping the Rooswijk shipwreck in order to bring back as much information as possible to start planning method, cost and people needed for the much bigger research that we may execute again with a large international team. Other options will also be taken into account  like (temporary) in situ preservation.  This all depends on what we will find.

The diving will finish on the 15th of September. The project already generated a lot of publicity and general interest in the Netherlands as well as in the UK.

More about the Rooswijk project:

Historic England (press release)

Cultural Heritage Agency (in Dutch) (persbericht)

Follow the project on Twitter using #Rooswijk1740

Searching underwater for the Van Bosse ship (1857)

A team of underwater archaeologists consisting of two members of the Japanese National Committee for Research and the Examination of Underwater Cultural Heritage Dr. Ikeda and Dr. Kimura, as well as mr. Sasaki from the National Museum of Kyushu and mr. Manders from the Cultural Heritage Agency of the Netherlands has arrived on Tarama island. This is one of the most Southwestern Islands of the Japanese archipelago, actually very close to Taiwan.

In November a Japanese team of professional archaeologists and sports divers associated with the only dive school on the island – Jaws 2 – will map and assess the site of the Van Bosse wreck and make it accessible for the sports divers who spend their holidays on the island. The visit now in August is mainly initiated as a start of the project about the Van Bosse shipwreck which includes also educational elements and archival research in several countries. The 22nd of August the team was welcomed by the department of education of the island that effectively is responsible for the management of this and other archaeological sites. They have assured us that all help in this is welcome. After this meeting we went to the dive shop to sort out our gears and then settled down in our condo which we share together.

The evening was used to discuss the possibilities to find elements of the wrecksite underwater and to pinpoint the exact place of wreckage, which is still not completely known. Dr. Kaneda wrote in 2001 an article ‘Historical Investigation concerning the Dutch Ship Van Bosse Wrecked Off the coast of the Tarama Islet’ and this article has also been discussed between the archaeologists in order to find out what the chances of finding wreckage are and what kind of research should be further conducted.

Van Bosse 2016 duik 1 (39) blog 2

The morning on the 23rd we were up early to go diving from the beach to the place where the ship according to accounts must have wrecked and where a fisherman has salvaged many pottery over the years. Indeed by walking on the beach we collected many pottery shards of different kinds. These are however mainly Chinese.

The coastal waters around the island Tarama are very shallow and abruptly become much deeper with here and there dangerous rocks ending just a few meters under the sea surface. For somebody who is not acquainted with these waters, it is a dangerous place. The underwater world, just at the edge of shallow and deep is however stunningly beautiful!

The second dive today was in deeper waters with the dive shop Jaws 2 and their ship. At 28 meters of depth, again on the edge of where the water gets very shallow and  near the place we had been diving in the morning, a considerable amount of pottery shards from large Chinese storage jars can be seen lying on the seabed. Were these used at the Van Bosse ship? It came from China…

Van Bosse 2016 duik 2 (19) blog 2

Also an enormous iron crate was discovered. Definitely something has happened here. The area however is large and the research in November should reveal the size of the site and maybe even also the location of impact: where the ship has hit the reef.

Tonight we will talk with an old fisherman. Let’s see if he can help us out.  Tomorrow, the 24th we are invited by the head of the island, similar to a mayor and in the afternoon we have a round up with the advisory board of the heritage of Tarama. Then up to Fukuoka for further talks at the Kyushu National Museum, our partner in shared heritage management.

Martijn Manders, maritime archaeologist/Head Maritime Programme RCE

Japanese – Dutch research on shipwreck Van Bosse about to begin

In August, the Cultural Heritage Agency of the Netherlands (RCE) is joining forces with the Kyushu National Museum to conduct an exploratory research on the Dutch shipwreck Van Bosse. The research focuses on exploring opportunities for mapping the Van Bosse and providing accessibility to the wreck for local sports divers. The project is a continuation of existing cooperation with Japan in the field of maritime archeology within the framework of Dutch Shared Cultural Heritage policy. The site of this Dutch wreck is already protected locally. The ship was built in Germany, but registered by the Dutch owner in Rotterdam.


The ship Van Bosse was originally built in 1854 in Germany. The 665t big three master barque, which was employed by the Bonke & Co. Trading in Rotterdam was on its way from Shanghai to Singapore when it sank during a storm in 1857 at Tarama island, Okinawa prefecture. Luckily all 27 people on board survived, but before they could return to Batavia in the Dutch East Indies, people stayed several months in Okinawa and integrated into the local community.

The story of the sinking of the Van Bosse and the interaction of the people of Tarama with the crew of the ship are recorded in detail. It gives us a good insight into the history of the Ryukyu Kingdom and the relationship that it had with foreign powers at a time when the self-isolationism of Japan had just been lifted. It is striking that until few years ago nobody knew exactly what ship it was, although the story of the sinking of the ship was well known. We know it now, thanks to extensive research in Dutch archives.

The Van Bosse shipwreck is registered as a Village Historic Site (オ ラ ン ダ 船 遭難 の 地: Oranda-sen Sonan no Chi ~ Site of Dutch ship wreck). It lies on a reef at depths ranging from a few meters to about 30 meters. Over the years, an iron anchor was lifted, which is on display in a local museum, and several other finds such as a complete Lucas Bols gin bottle and some salvaged porcelain shards.

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However, there’s more to be found. Despite the protected status of the ship an archeological significance assessment of the wreck site has not yet been made. This will take place this autumn and is having its official start now in August, with a first joint visit to the site. Ultimately this will lead to a management plan for the site in which all interests should be taken into account. The Van Bosse wreck is already dived regularly by sport divers. A local dive shop has voluntarily undertaken protection of the site. The local authorities are working on an active promotion. The aim is to use the wreck to attract more recreational divers to the island. But what measures are necessary to facilitate an intensive visit of sports divers? How, for example, can the remains underwater be protected while still visible and accessible to visitors? And there is need for more information about the site to allow divers to fully experience the wreck and its history when they are underwater.

In August Dr. Ikeda from the University of Okinawa, Dr. Jun Kimura of the Tokai University in Tokyo (with students), Randy Sasaki of the Kyushu National Museum and Martijn Manders (RCE)  will officially start the project. In November, the Japanese partners will conduct follow-up research historical research in the Netherlands and Germany will be coordinated by the RCE.


Late August the World Archaeological Congress (WAC http://wac8.org/) will be held in Kyoto, Japan. As part of the Japanese – Dutch cooperation Martijn Manders and Yoshihi Akashi will represent the Fukuoka prefecture and chair the session ‘Global Perspectives on Underwater Cultural Heritage Management’. The presentations will elaborate on universal values of the underwater cultural heritage management, what needs to be improved in management and the way countries can cooperate in the protection of underwater cultural heritage. This fits exactly with the way the research on the Van Bosse shipwreck is implemented: a collaboration between various parties in the country where the ship sank, Japan, and the country of origin, the Netherlands.

Martijn Manders, maritime archaeologist/Head Maritime Programme RCE

Remote sensing process & the big blue

Lees deze blog in het Nederlands

Remote sensing

A crucial element in the project is the remote sensing process. The aim is to acquire, process, analyze and interpret the data and to let this follow by diving on targeted locations.

We have acquired the data with a seaborne magnetometer. This device measures distortions in the natural earth’s magnetic field through the presence of iron (or ferrous) material on or under the seabed. The magnetometer is towed on a cable behind the survey vessel, sending readings up the cable to a tablet, which logs the data and provides positioning through a GPS.

Photo 1

Photo 1: The results of magnetic testing over know iron wreck site, Eidsvold, at Christmas Island. The image on the left clearly show distortions in the earth’s magnetic field, caused by the presence of the wreck. The three lines show the track of the survey vessel. The image on the right show a profile of a transect line across the sight with the clear characteristic ‘dipole’.

The tablet also helps the skipper to navigate along per-positioned lines called transects. These lines have been carefully arranged in mapping software to be straight, and parallel. Narrow line spacing is required to allow sufficient coverage.

Once the data is brought back ashore, it is reviewed on laptops with specialized software. This process allows for the earth’s magnetic field to be displayed and any distortions detected. Interpretation happens next.

Photo 2

Photo 2: A magnetic anomaly discovered in the post-processing phase of the remote sensing component in the search. The anomaly is clearly seen in the paler contour lines, along with depth contour lines. This anomaly is approximately 85 by 160 meters.

A list of potential sites is produced, and the most promising analyzed more closely. Mapping software allows for the precise positioning for the deployment of divers. Circular shapes are created and placed within the mapping software, which gives a very accurate indication of depths, and can thus inform the dive plan. In this case planning for circular dive searches.

This positioning information is then fed into the tablet, enabling precise navigation to each target.

Photo 3

Photo 3: Mapping and other specialized software enable the blending of magnetic isometric lines (black) and magnetic anomalies (blue and yellow), with bathymetric contour lines (white) and planned circular dive searches (red).

The entire work flow, carried out by Alex Moss and James Parkinson enables the team to react to information gathered in the field, a sort of ‘reflexive methodology’.

Penultimate day of diving on Christmas Island

Waterlogged is the best way to describe the way we all feel after the last few days. Whether diving or on the boat we have been wet. Some rain showers were so strong it was a drier feeling in the water than out of it! Sadly, our time on Christmas Island is coming to a close and we have not discovered any archaeological material that would bring us closer to the Fortuyn. While we have not yet managed to dive all the identified magnetic anomalies our time is running out. But let’s keep our fingers crossed.

DCIM100GOPROGOPR3506.Photo 4: Me descending down the shotline.

DCIM100GOPROGOPR3534.Photo 5: Alex Moss doing a 30 meter circular search. The other diver holds the line at 15 meter and makes sure the line doesn’t get caught.

Today we dived sites off the West coast and because of the very calm conditions were able to swim survey from Egeria Point northwards to Winifred Beach. The difficulty of finding a site in the 30 meter depth range available to us as divers was made very evident during that transect, as several times we encountered a vertical drop off to far greater depths not more than 50 meters from the coastline. A very small shelf for a shipwreck or shipwreck debris to stay attached to!

DCIM100GOPROPhoto 6: Graeme and Shinatria after their circular search.


Photo 7: The MV Eisvold shipwreck is a beautiful place to dive!

Our next blog will be the last from Christmas Island, before we go to Cocos Keeling. Stay tuned!

Speuren naar scheepswrakken op de bodem rondom Christmas Island

Read this blog in English

Begroet met een prachtige zonsopgang boven het kalme water en met een volle maan die nog steeds helder scheen, hebben we het veldwerk voortgezet. De afgelopen dagen hebben we de zuid- en westkant van Christmas Island onderzocht.


Photo 1 high res
Robert de Hoop en Shinatria Adityaram met de magnetometer die we gebruiken voor het onderzoek

Photo 2 high res

Dit is hoe het eruit ziet als de gegevens binnenkomen. Aan de linkerkant de data van de magnetometer en rechts de gegevens van de side scan sonar aan boord

25 februari

We brachten de dag door op het water met Azmi Yon, Renata de Jong en Rob Muller van Parks Australia. Het weer was uitstekend en we zijn erin geslaagd om in de buurt van de kust op een aantal zeer weersafhankelijk plekken te komen, in de buurt South East Point en Egeria Point in het zuidwesten. Met de hulp van Graeme ben ik op zoek gegaan in de digitaal beschikbare archieven over een ander Nederlands schip dat zeker op Christmas is vergaan.. Het is de Vice Admiraal Rijk (1852). Het schip is vernoemd naar genoemd naar Julius Constantijn Rijk (1787-1854),  Nederlandse viceadmiraal, gouverneur-generaal van West-Indië en minister van Marine. De komende twee weken laten we het onderzoek naar dit wrak meelopen met het overige onderzoek.

Photo 3
Een technische tekening van de Vice Admiraal Rijk (maritiemdigitaal.nl)

Vice Admiraal Rijk

De Nederlandse bark Vice Admiraal Rijk werd in 1843 gebouwd door de werf Gips in Dordrecht voor de rederij A. Ahlers uit Amsterdam. Het was op reis van Ramsgate naar Batavia in 1852 toen het tegen de zuid-westelijke punt van Christmas Island aanliep. Het schip zonk met alle zeilen bij. Vier van de 20 mannen hielden zich vast aan het drijvende dak van een roef en dreven naar de noord-westelijke punt van het eiland. Toen ze probeerden aan land te komen en de kliffen te trotseren, werd een bemanningslid meegesleept door een terugtrekkende golf en verdronk. Slechts drie mannen overleefden de ramp dus maar! Zij zijn na 56 dagen te hebben overleefd op het eiland uiteindelijk gered. Het team heeft anomalieën waargenomen bij de zuid-westelijke punt en denkt daarbij aan het wrak van de Vice Admiraal Rijk. Identificatie moet de komende tijd dus gaan plaatsvinden.

Graeme Henderson geeft een presentatie aan de kinderen van de Christmas Island District High School

26 februari – Graeme en Andy gingen naar de Christmas Island District High School en gaven vier  presentaties over het project en de scheepswrakken van de Christmas en Cocos Keeling eilanden voor de kinderen uit groep 4 tot en met 12. Graeme overhandigde de school een exemplaar van zijn boek, Unfinished Voyages. De school was erg blij met deze aanvulling op hun bibliotheek. Alex, James, Shinatria en Robert gingen met Azmi verder met het onderzoek langs de zuid- en westkust, opnieuw de gebieden verkennend die de vorige dag waren onderzocht.

Photo 5
James Parkinson en Azmi Yon op de boot van Parks Australia
Photo 6
Alex Moss, onze GIS-deskundige die met James Parkinson alle gegevens gaat verwerken die we hebben verworven om te bepalen wat de beste locaties zijn om te gaan duiken

De weersomstandigheden zijn ontzettend goed geweest tot dusver. Op zich niet heel erg verrassend, omdat we bewust naar dit eiland zijn gekomen tijdens het beste seizoen voor een kalme zee, namelijk het  cycloon seizoen. Dit klinkt waarschijnlijk wat raar, maar het water is dan normaal gesproken op haar kalmst. We hopen natuurlijk een cycloon te vermijden want dan is verder onderzoek op zee uitgesloten.  Maar ook in dit seizoen is de deining heel groot omdat het water over grote afstanden aan komt stromen voordat het op relatieve ondiepe bodem terecht komt. Door die zware deining is een rechte koers houden al erg lastig. De aanzwellende golven vanuit de Indische Oceaan raken de kalkstenen kliffen van Christmas Island en slaan terug waardoor het zeewater eruit ziet alsof het aan de kook raakt: grote witte schuimkoppen en water dat de lucht in spuit. De effecten van de deining worden zelfs nog  verder verergerd door wind en stroming. Om maar niets aan het toeval over te laten, zullen de teamleden zondag een bezoek brengen aan de tempel van de Godin van de Zee en haar bedanken in naam van de archeologie.

Photo 7
Terugkeren naar het hotel na een geslaagde dag veldwerk!
Photo 8
We staken een kaars aan in de tempel van de Godin van de Zee

Robert de Hoop


The search for the Fortuyn has begun!

Lees hier de blog in het Nederlands

Main photo
Illustration by Daniel Beeckman, made when he sailed past the island in 1714

Yesterday the ‘Closing in on the Fortuyn’ project started and in the coming weeks you can read all about the search for the Fortuyn on this blog! The Fortuyn is a Dutch East India Company ship that was last seen in January 1724 at the Cape of Good Hope on its way to Batavia (nowadays Jakarta) in the East Indies. The project is a collaboration between Wreck Check Inc., the Maritime Programme of the Cultural Heritage Agency, the Dutch Embassy in Canberra, the Silent World Foundation, Parks Australia, the Western Australian Museum and the Department of Environment.

Photo 1
Team members for the 2016 Fortuyn project with Parks Australia staff
Photo 2
Andrew Viduka and Graeme Henderson

A team of international archaeologists will be searching for the remains of the VOC ship the Fortuyn in Australia on the Christmas and Cocos Keeling Islands. My name is Robert de Hoop, I’m a maritime archaeology student and I am very lucky and proud to join this experienced team on this amazing project. The next three weeks I will be writing every other day about my experiences here and how the search is progressing. For me it is an amazing opportunity to get experience in the maritime field, not only in diving but also with the other surveying techniques that will be used. The diving will be completely different than what I am used to with amazing visibility under water and potentially somewhat bigger animals (sharks..). In the next couple of blogs, I will introduce also the other five members of the team.

Photo 3
Conditions faced by the intrepid team members

The reason that the search takes place on the Christmas and Cocos Keeling Islands is because historical research, done by the Cultural Heritage Agency of the Netherlands and the University of Leiden (by Martijn Manders and Pablo Boorsma) and Australian archaeologists, has indicated that the Fortuyn may have been wrecked on the coast of Christmas and/or Cocos (Keeling) Islands. The historical research suggested that the south and west coasts of either location are the most likely places of wrecking. During the monsoon season, Dutch skippers were directed to take the western route past Christmas and the Cocos Islands, rather than the eastern route past the Australian continent.

Photo 5
James Parkinson and Alex Moss working to set-up the magnetometer and software

In 2015 the Wreck Check team searched the seabed around the Christmas and Cocos Keeling Islands with a magnetometer. A magnetometer records differences in the earth’s magnetic field. Steel or iron material, will cause distortions in the field, creating anomalies. A magnetometer will detect a steel hulled vessel relatively easily, but the Fortuyn has a wooden hull and rather than one enormous reading, the result may be a number of small, scattered readings. This reading could have been caused for instance by the 36 cannons and the approximately 8 anchors that were on board. Once an anomaly was observed the position of the boat was recorded using GPS. This year the team is going back to check these anomalies. The southern part of the island will be redone with a higher resolution magnetometer and then spots will be chosen where a diving survey will take place. Post fieldwork analysis has also revealed a number of anomalies on Cocos (Keeling) Islands that require further investigation. The anomalies, particularly the one on the west side of South Point, fit with the identified wrecking profile, and require ground-truthing to ascertain whether the signal variations were caused by cultural features or geology.

Photo 6
Pre-dive briefing to team members given by Wreck Check Inc dive officer James Parkinson
Photo 7
Robert de Hoop and Graeme Henderson translating a report of the wrecking of the Vice-Admiral Rijk on Christmas Island

Yesterday the team arrived on Christmas island, unpacked and settled in. Today we’ve been setting up, going over safety and making a plan for the coming days. Together with Graeme Henderson, from Wreck Check, I started on translating some Dutch historical texts to English, which talk about other ships that wrecked near or on Christmas Island. We do this because there is a chance that we will run into other wrecks and the team wants to have a nice overview of all the possible shipwrecks and their potential locations. More on these other wrecks will follow in another blog. In the afternoon we tested the magnetometer on the Eidsvold. This is a World War II cargo wreck made of metal, so an ideal site to check the magnetometer. The next two days we will spend doing a couple of transects on the south and west coast of Christmas Island to find the best spots where we will be doing diver surveys. We hope you check back in the coming days to meet the team and follow the search!

Robert de Hoop

De zoektocht naar de Fortuyn is begonnen!

Read this blog in English 

Main photo
Tekening van Daniel Beeckman, gemaakt toen hij langs het eiland voer in 1714

Gisteren is het ‘Closing in on the Fortyn’ project van start gegaan. De  komende drie weken kun je ons volgen bij de zoektocht naar de Fortuyn op deze blogpagina. De Fortuyn is een Nederlandse Oost-Indiëvaarder die voor het laatst is gezien in januari 1724 bij Kaap de Goede Hoop. Het schip en haar bemanning was op weg naar Batavia (tegenwoordig Jakarta) in Nederlands Oost-Indië. Het project is een samenwerking tussen Wreck Check. Inc., het Maritiem Programma van de Rijksdienst voor het Cultureel Erfgoed, de Nederlandse Ambassade in Canberra, de Silent World Foundation, Parks Australia, het Western Australia Museum en het Department of Environment.

Photo 1
Teamleden van het Fortuyn project 2016 met de medewerkers van Parks Australia
Photo 2
Andrew Viduka en Graeme Henderson

Een international team van archeologen start hun zoektocht naar de overblijfselen van het VOC schip de Fortuyn in Australie nabij Chrismas Island en de Cocos Keeling Islands. Mijn naam is Robert de Hoop, ik ben een student maritieme archeologie en ik heb het ontzettende geluk deel uit te maken van dit ervaren team binnen dit geweldige project. De aankomende drie weken zal ik jullie om de dag meenemen in onze zoektocht en onze ervaringen delen.

Photo 3
De omstandigheden waar de heldhaftige teamleden vandaag in moeten werken

De locaties Christmas Island en Cocos Keeling Islands zijn geselecteerd op basis van de conclusies van het historische onderzoek dat is uitgevoerd door de Rijksdienst voor het Cultureel Erfgoed, Universiteit Leiden (door Martijn Manders en Pablo Boorsma) en Australische archeologen. In het historisch onderzoek komt naar voren dat de grootste kans voor de wraklocatie van de Fortuyn zal liggen aan de zuid- of westkust van beide eilanden. De reden hiervoor is dat gedurende de moesson periodes de Nederlandse schepen langs de westelijke routes geleid werden in plaats van de route langs de oostkust van het Australische vasteland.

Photo 5
James Parkinson en Alex Moss installeren de magnetometer en software

In 2015 heeft het Wreck Check team al een onderzoek uitgevoerd rond Christmas Island en de Cocos Keeling Islands met een magnetometer. Zo’n magnetometer registreert verschillen in het aardmagnetische veld. Materiaal van staal en ijzer zorgt voor vervormingen in het veld en daardoor worden afwijkingen gedetecteerd. Een magnetometer is zo in staat om stalen wrakken makkelijk te traceren, de Fortuyn is echter een houten schip waardoor het resultaat slechts een aantal kleine verspreide metingen oplevert. Deze registratie kan zijn veroorzaakt door bijvoorbeeld de 36 kanonnen en de ongeveer 8 ankers die aan boord waren  van het schip. Zodra een anomalie is waargenomen  wordt de positie vastgelegd met GPS. Dit jaar keert het team terug om de in 2015 waargenomen anomalieën te controleren. Het zuidelijke deel van het eiland zal met een hogere resolutie magnetometer worden onderzocht.  Op basis hiervan zullen de locaties uitgekozen worden waar nader onderzoek zal plaatsvinden en gedoken wordt. De veldwerkanalyse heeft ook aangetoond dat een aantal anomalieën op de Cocos Keeling eilanden nader onderzoek vereisen.

Photo 6
De briefing van de teamleden voor het duiken, door duikploegleider James Parkinson van Wreck Check Inc
Photo 7
Robert de Hoop en Graeme Henderson vertalen een verslag van de vice admiraal Rijk over de scheepsramp

Gisteren is het team aangekomen op Christmas Island , zijn alle spullen uitgepakt en hebben we ons gesetteld. Vandaag hebben we een planning voor de komende weken gemaakt, de apparaten en instrumenten die voor de zoektocht nodig zijn, zijn ook getest. Samen met Graeme Henderson van Wreck Check ben ik begonnen met het vertalen van enkele Nederlandse historische teksten in het Engels. Deze historische bronnen maken melding van andere schepen die vergaan in de buurt van of op Christmas Island. We doen dit omdat er een kans bestaat dat we ook andere wrakken zullen tegenkomen en het team wil daarom een mooi overzicht maken van alle mogelijke scheepswrakken en de mogelijke wraklocaties. Meer informatie over deze andere wrakken zullen volgen in een andere blog. In de namiddag hebben we de magnetometer getest op de Eidsvold, dit is een Tweede Wereldoorlog vrachtschip wrak van metaal, dus een ideale plaats om de magnetometer controleren. De komende twee dagen zullen we onderzoek uitvoeren aan de zuid- en westkust van Christmas Island.

We hopen dat je ons blijft volgen de komende dagen en je zult dan ook kennis maken met de rest van het team.

Robert de Hoop

National Geographic volgt samen met ons de zoektocht naar de Fortuyn!

Day 10: The West Site Story

Today we completed 16 dives. We have finished drawing, measuring and filming the western part of the site and have now started on the eastern part of the site OVM10. On the western part of the site we have found a lot of different ship parts. For instance, the stern and the keel. Piece by piece the overall picture of the ship is emerging.

Although the site is harder to interpret with all the scattered fragments of the ship, the photogrammetry process is going a lot faster because of the coded targets we applied. It is much easier to align the different chunks of stills from the videos and this makes it easier to see what has been properly filmed. The photogrammetry experts are then able to tell the divers which parts still need to be filmed to give us a complete picture of the site.

Part of the site that we have processed in Photoscan
Part of the site that we have processed in Photoscan

We took some dendro samples yesterday and today we prepared them for analysis. This requires measuring each individual piece, recording and labelling. We truly hope the samples will be good enough for dating, since many of them do have wide year rings. The samples that were taken may have come from production forests. These forests produced specific trees for the shipbuilding industry from the late 17th century onwards. This is however, problematic for us as it is harder to date the wood using  dendrochronology. We’ll know more when the analysis is done.

Preparing the dendro samples for analysis
Preparing the dendro samples for analysis

Diving will continue this weekend and the pack-up will commence on Monday. The field school is wrapping up and some of the crew are leaving this evening.

Robert de Hoop (intern Maritime Programme)
Bronwyn Hughes (Leiden University)

Day 9: The condition of the OVM 10

We have found a lot of burned wood on the OVM 10. This might be the reason for sinking, but maybe it happened only after the ship was deserted. We will probably never know. The structure however must have burned for quite a while, based on the severity of the burning marks on the individual timbers.

The ship parts emerging from the sediment are quite degraded by Teredo navalis or shipworm. The timbers became exposed after the sand extraction for the Maasvlakte 1, but also other activities in the lake. Some structural elements on OVM 10 only became exposed recently due to illegal airlifting. This wood still hasn’t been attacked by the shipworm but is obviously very vulnerable for future attack.

An example of the burned wood that we found
An example of the burned wood that we found

The site has been particularly difficult to research, because it is not structurally intact and pieces of the ship are strewn about the lake floor. A hypothesis was suggested that this did not occur at or around the time of the ship’s sinking but could be a result of the dredging that took place. This could explain why so many of the planks and beams are sticking up out of the sand. The fact that beams and planks are also cracked and splintered at the ends, supports this theory.

Diver getting ready
Diver getting ready

The sandy bottom has also been a challenge to our divers who have to be careful not to kick up the sediment when taking measurements as this can decrease visibility. In general, visibility has been reasonable, around 3 meters. This is good enough for our photogrammetry recording.

Good visibility today
Good visibility today

Today divers took some dendro samples from different parts of the ship. These will be taken away for analysis to determine the age of the wood and where the tree was felled. Analysis will also be done to show the effect the shipworm has had on the wood as well as the bacteriological decay.

Degradation of the wood by the shipworm
Degradation of the wood by the shipworm

Most of the measurements have been taken and entered into Site Recorder and the picture of where each and every detected structure element is positioned is becoming clearer every day. The work the divers have been doing is very accurate and we are happy with the results so far.

Tomorrow some of the team members will be leaving us, so they will be wrapping up their work assignments of the project and saying their farewells.

Robert de Hoop (intern Maritime Program)

Bronwyn Hughes (Leiden University)

Day 8: Triangulation and trilateration

Today was already the third day of our campaign on the OVM 10. The whole day we were drawing, measuring and filming. We also tested so called ‘coded targets’ which should make the photogrammetry a lot easier. More on this, see below.

Now that we are familiarized with the site and have an overall picture of what is down there we are able to start taking measurements. We do this by selecting datum points which allow us to work in a precise way. These points correspond to different features or locations of the site. The measurements are made by using a method called triangulation. Measurements are taken between three different points, they are recorded underwater and once the diver brings them up to the surface they are entered into a computer program called Site Recorder. Site Recorder immediately tells you if you measured correctly and what the margin of error is. With all of these measurements we gather we are then able to draw an ever more accurate site plan and they can be used alongside the photogrammetry software.

Entering the measurements in Site Recorder
Entering the measurements in Site Recorder

For the OVM 10 we are trying out coded targets. These coded targets are attached to wood and/or are placed between different objects on the site. The coded targets are necessary for this site as recognition points because the site is spread out over a large area, with frames and deck beams surfacing the seabed.Between areas of sediment there are few features to detect. After stills are taken from the GoPro footage, Photoscan software can detect the coded targets in these photos more easily and align them much faster.

Lots of activity on deck
Lots of activity on deck

Three days ago we started off with a rough sketch of the site. Already we have a much better understanding of what is left on the Oostvoornse lake bed. With the actual measurements of the ship elements and their spread, step by step we are geting a good idea of what is there and what the significance is of OVM 10. The filming underwater is harder to do than on OVM 12 because of the spread of the elements and the visibility that is less here. This is why – as a backup – we will also use the conventional methods to record the site with additional drawing.

A coded target that is placed on the site
A coded target that is placed on the site

A large spread, interesting features, lots of illegal excavation done and wood exposed recently. What can we say about the condition of the site? More about that tomorrow.

Robert de Hoop (intern Maritime Programme)