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Exhibition texts Archaeology under the water

Instruction

Move counterclockwise through this part of the exhibition.

It takes just under 10 minutes to have the text read out.

Archaeology under the water. Above exhibit.

Maritime archaeologists examine objects and other remains left behind by humans, either under water or near water. We are needed wherever cables or pipelines will be laid and where ports, bridges and other structures will be built. We search for everything from settlements and defensive works to shipwrecks of various kinds.

In Sweden, all wrecks from before 1850 are considered ancient monuments and are protected by the Heritage Conservation Act. Sometimes more recent wrecks can also be classified as ancient monuments. This protection means that you are allowed to dive and look at these wrecks, but you need permission to excavate.

Dive down and document

Working under water must be effective – after all, time is limited beneath the surface. It is important to plan carefully and read up about the site. Among the first things maritime archaeologists do when they dive to examine a wreck is to determine how old it is.

What does the wreck look like, how is it constructed? Is there any cargo or objects left there? We photograph, record and draw what we see. Sometimes we collect samples that can help us determine the ship’s age.

Camera with underwater housing. In exhibit.

Photographing and filming sites and wrecks is a big part of our work beneath the surface. A standard camera can be mounted in a waterproof camera housing. A dive light is important since water absorbs light and colour.

Tree-ring sample. Next exhibit.

The age of wood can often be determined by studying its tree rings. This is called dendrochronology. In the film, a sample is taken of a plank from the warship Resande Man. The analysis showed that the tree the plank came from was felled in the 1640s.

Different search tools. Text on leaning panel.

It can be difficult to find remains – often even more difficult in water than on land. Searching through large areas in dark, murky waters takes divers a very long time. But there are technical solutions that make it easier.

Among the tools used today are different types of sonar: conventional depth sounding sonar, side scan sonar and multibeam. These tools measure in different ways how long it takes for a sound wave to bounce from the bottom of the sea or against an object. Unlike light and radio waves, sound waves travel faster and farther in water than in air. Here on the left you can find out more about how the different techniques work.

The graphic to the right shows the principle of the three search tools.

Wall above leaning panel

Norrahamnsvraket, sonar

The conventional sonar measures the distance straight down using a single beam of sound waves. A digital image of the depth profile of the seafloor can then be created. Conventional sonar only take measurements straight down.

Ingrid Horn, side scan sonar

This instrument sends and receives sound waves both downwards and off to the sides. Objects sticking up from the bottom cast acoustic shadows, which can reveal the shape of a wreck or other feature. An effective tool.

Nåttarövraket, multibeam sonar

Multibeam sonar emits a spread of sound pulses in the shape of a fan. A digital 3D map of the seafloor is created, which can be rotated and viewed from any angle. An effective but somewhat insensitive tool.

Three finds. Interactive station

On the panel are photos from three finds. Select with the button below the image. A ROV film from the site is shown on the larger display. The smaller displays above show the position of the site on nautical charts, a zoomed out and a zoomed in position.

The station has no text.

R O V's – A diving aid

R O V stands for Remotely Operated Vehicle, and is a remote-controlled underwater robot. They can come in different sizes and are usually equipped with a camera, lights, GPS and a manipulator arm.

A R O V has virtually unlimited dive time and is handy in places where it is dangerous to dive or where it is very deep. It can be a bit clumsy and does not perform very well when multiple samples must be taken, or when sensitive materials and fragile objects must be handled. An experienced archaeologist diver is also better at assessing and evaluating an artefact directly on site.

Stories from a dive boat. Interactive movie station.

Three martime archaeologists tell in films with sound and text. Select movie with the buttons on the panel.

A moment frozen in time. Short wall.

Just north of Dalarö in the Stockholm archipelago lies an unusually well-preserved shipwreck. Archaeologists believe that it is the ship Bodekull, built in 1660 in Blekinge in southern Sweden. Down by the wreck, you get the feeling that time has stood still. Various tools and objects can be found right where they were left. A few ceramic jars still rest on a beam in the stern and a cannon is left in its gun carriage.

Over the years, maritime archaeologists from several institutions have examined the wreck. They have filmed, taken photographs, made meticulous drawings and produced a detailed 3D model of the wreck. Some things, like the big figurehead – a lion – were too difficult to record on site. They were brought up, documented and then put back.

In horizontal exhibit, film, pictures and objects

At the bottom of the stand, film sequences from the wreck are shown.

One wreck, two images

Archaeologists document sites using both orthophotos and drawings. An orthophoto, like the bottom image, consists of several photos taken from above. They often contain too many details. In a drawing, the archaeologist can choose what to make visible.

Drawing on a slate

Underwater, archaeologists draw on a waterproof drafting film attached to a slate. A pencil works fine, but you have to lie still, without stirring up sludge and sediment. A plan of an entire site usually consists of several merged images.

Your assignment. A game in three parts.

Dive down and document. First part of the game.

A virtual dive. Sit down on a stool and grab the handel under one of the dive masks. It is the same content in three. The controls you need to use are on the handle.

During the dive, you and a colleague examine a wreck together. The instructions are given with spoken dialogue, texted prompts and visual illustrations.

 


Proceed to next part: Maritime archaeologial workshop

Back to The Assignment, introduction

Back to start

Page last updated: 2021-09-10