Wrecks on the Seabed R2: Assessing Evaluating and Recording (Unknown)
Wessex Archaeology, 2012. https://doi.org/10.5284/1017439. How to cite using this DOI
Data copyright © Wessex Archaeology unless otherwise stated
This work is licensed under the ADS Terms of Use and Access.
Primary contact
Wessex Archaeology
Portway House
Old Sarum Park
Salisbury
SP4 6EB
UK
Tel: 01722 326867
Fax: 01722 337562
Resource identifiers
- ADS Collection: 1155
- ALSF Project Number: 3877
- DOI:https://doi.org/10.5284/1017439
- How to cite using this DOI
Overview
The digital archive for this project submitted to the Archaeology Data Service consists of the following files:
- A database recording the diving information from the wreck of the unknown steamer
- 43 images taken as video stills from the five dives
- GIS shapefiles of the dive tracks
There is data from a total of five dives on the wreck of the unknown steamer, there are video stills, GIS shapefiles for five dives, plus observations extracted from the database. The 'DIVA' database contains dive summary information.
The ROV System
The Remotely Operated Vehicle (ROV) and ROV operator were supplied by Subsea Vision Ltd. and a Seaeye Falcon ROV was used. The ROV was fitted with a Tritech Typoon Zoom video camera, a Tritech Tornado Low Light Monochrome video camera and three 75 watt lights.
In addition, a Kongsberg oe14-208 underwater digital stills camera (a Canon Powershot G5 in a Kongsberg housing) with oe11-202 flashgun and a Tritech ISS scaling camera were mounted on an under-slung module for some dives.
The digital stills camera could be operated through a Graphical User Interface (GUI) on a surface computer which gave full control of all camera settings. The captured images were temporarily stored in the on-board memory of the camera and were then downloaded on the surface.
The Tritech Image Scaling System (ISS) consists of a PAL colour zoom video camera with six lasers. Four of these lasers provide parallel beams, while two lasers are mounted at predefined angles to provide reference points. To measure an object, a video screen capture has to be taken with the lasers pointed at the object. The screen capture is then imported into the ISSSOFT package after the dive, where the image can be analysed and measurements can be taken.
The ROV was equipped with forward scanning Tritech Mini King sonar for navigation, a built in fluxgate compass and a digital depth gauge. Information from these instruments could be displayed over the video output.
The surface controls consisted of the main ROV surface unit, a hand controller with joystick, a screen, two PCs for sonar display and digital stills camera control and a Sony digital video capture unit. Video was recorded on miniDV tapes (which are held in hard copy by Wessex Archaeology).
The Acoustic Tracking System
An Ultra Short Baseline (USBL) SCOUT acoustic tracking system from Sonardyne was used during all fieldwork sessions to track the ROV.
The SCOUT system consists of three main components: the vessel mounted acoustic transceiver, one or more Remotely Operated Vehicle mounted transponders and the surface command module running the control software.
In a USBL system, the position of subsea targets is calculated by measuring range and bearing from the vessel mounted transceiver to the submerged transponder, which emits acoustic signals. In a short baseline system, only one transducer (transponder on the seabed) transmits sound, but many transducers on the surface receive signals. In a USBL system such as SCOUT this array of transducers is built into a single transceiver assembly. The baselines between the individual transducers are very (ultra) short, usually in the range of centimetres. The waterproof and portable surface command module running the SCOUT USBL software was installed in the control room.
The SCOUT USBL Transceiver was mounted on a pole over the side of the vessel. In order to provide maximum stability for the transceiver the pole had a diameter of 10cm and was attached to a bracket welded onto the rail and supported by another bracket further down the ship's side.
SCOUT's Type 7815 HF transponders were attached to the Remotely Operated Vehicle.
The transponder worked on frequencies between 35 and 55kHz. The stated operating range for the system was 500m and the acoustic coverage was +/- 90 degrees below the transceiver.
For the Remotely Operated Vehicle sessions, an external MRU (TSS HRP-10 MRU) and gyrocompass (ASG Brown Meridian Surveyor gyrocompass) were installed on the vessel. GPS was provided from a CSI Vector Sensor Differential GPS capable of sub-metre accuracy.
Prior to the fieldwork, all instruments were surveyed on the vessel using a total station and offset values input into relevant software. Full calibration of the SCOUT software was undertaken prior to operations.
