| id |
655 |
| cruise |
WESSEX3B
|
| nav_equip_type |
Differential GPS
|
| accessuse_restric |
unrestricted use, copyright acknowledgement
|
| ship |
Xplorer
|
| geophys_equip_type |
CHIRP Sub-bottom Profiler, Echo Sounder, Sidescan Sonar
|
| terms_of_use |
Available under the Open Government Licence subject to the following acknowledgement accompanying the reproduced Historic Scotland materials "Contains Historic Scotland materials ©Crown Copyright [year]"
|
| client |
Wessex Archaeology
|
| samp_equip_type |
None
|
| terms_of_use_url |
http://nationalarchives.gov.uk/doc/open-government-licence/version/3/
|
| restitle |
Geophysical Survey WESSEX3B: (23/Aug/2006 to 23/Aug/2006)
|
| start_date |
2006-08-23 00:00:00
|
| contractor |
Wessex Archaeology
|
| start_date_est |
Real
|
| cruise_data_url |
None
|
| cruise_area |
CP2 Regional Sea Boundaries: Minches & Western Scotland, Offshore 1:250k: Tiree, SeaVoX Sub-Ocean: INNER SEAS OFF THE WEST COAST OF SCOTLAND
|
| end_date |
2006-08-23 00:00:00
|
| mdfileid_nerc_guid |
c5bc60cd-04e9-3862-e044-0003ba9b0d97
|
| abstract |
Wessex Archaeology was commissioned by Historic Scotland to undertake an Undesignated Site Assessment of the site known as the Tobermory Galleon in Tobermory Bay, Mull. The work was undertaken as part of the Contract for Archaeological Services in Relation to the Protection of Wrecks Act (1973). The assessment was carried out in advance of possible further commercial salvage work on the site. Wessex Archaeology conducted a geophysical survey at three sites within Tobermoray Harbour on the 23rd August 2006. The survey was conducted from the S/V Xplorer. A geophysical survey was followed by diver ground-truthing of anomalies was carried out to confirm the position, extent, stability and character of any significant archaeological deposits. The survey showed that part of the wreck and debris fields from both the sinking and subsequent salvage may still exist although the precise nature, extent and position of archaeological deposits associated with the wreck, in particular any surviving coherent ship structure, remained unclear. The survey included single beam echosounder, sub-bottom profiler and sidescan sonar. The geology and geophysics component of the data are archived at British Geological Survey (BGS) MEDIN Data Archive Centre (DAC) for Geology and Geophysics. Data were also provided to other archive centres as appropriate.
|
| end_date_est |
Real
|
| cruise_alias |
None
|
| additional_info |
Throughout the survey all co-ordinates were expressed in WGS84, UTM zone 29N. Single beam bathymetric data were recorded throughout all stages of surveying and was acquired using a Knudsen 320M single beam echo sounder. The echo-sounder transducer was mounted to the survey vessel, and the transducer draught was measured and entered into the echo sounder to obtain depths relative to the sea-surface. A TSS DMS 2.05 motion sensor was rigidly mounted above the transducer to measure the vertical displacement (heave) and attitude (roll/pitch) of the vessel; this data was interfaced with the echo sounder. The accuracy of the draught and velocity offsets were checked at the start of the survey using the bar check method. Sub-bottom profiler data were acquired using a chirp system. The chirp system used was the new EdgeTech 3100P portable sub-bottom profiling system using a SB-126S tow vehicle. The chirp is a high resolution wideband frequency modulated sub-bottom profiler. The system transmits a frequency modulated pulse that is swept over a full spectrum frequency range (in this case 2-12 kHz). The vertical resolution using 2 – 12 kHz frequency is 8cm and in an area of silts and clays, which is typical for the survey areas of concern, the typical sub-seabed penetration is expected to be up in excess of 10m. Sidescan sonar data were acquired using a Klein 3000 dual frequency towfish. This system collects data at 125kHz and 445kHz simultaneously. The Klein 3000 collects data at both high and low frequencies and therefore produces high quality images suitable for archaeological purposes. High and low frequency data were acquired at a range of 75m throughout the survey. Due to the number of moorings and moored vessels in the harbour navigating along planned survey lines was not always possible. However, full coverage of sidescan sonar data was ensured by acquiring sidescan sonar data at a smaller line spacing and running infill lines where necessary.
|
| confidentiality |
unclassified (open file)
|
