Geophysical Investigations of the Cattewater Wreck 1997-2007
Total Page:16
File Type:pdf, Size:1020Kb
Geophysical Investigations of the Cattewater Wreck 1997-2007 Reference: PLYCAT_07GEO August 2010 Geophysical Investigations of the Cattewater Wreck 1997-2007 Geophysical Investigations of the Cattewater Wreck 1997-2007 Prepared by: Peter Holt 3H Consulting Ltd. 6 Honcray, Plymouth, PL9 7RP UK [email protected] © Copyright 3H Consulting Ltd 2010 Cover image from Great Britain’s Coasting Pilot chart 16, Collins 1693 Title Geophysical Investigations of the Cattewater Wreck 1997-2007 Description A summary of the geophysical survey work undertaken on the Cattewater Wreck, Plymouth, UK (NMR 1082125), site code PLYCAT Reference PLYCAT_07GEO Subject Maritime, wreck, watercraft, museum, designated wreck Coverage Village – Turnchapel, Town – Plymouth, County – Devon, Country – United Kingdom, Period 16th Century Creators Peter Holt Publisher 3H Consulting Ltd Dates August 2010 Version 1.1 Copyright 3H Consulting Ltd Language English Resource type Document Format Portable Document Format (PDF) Acknowledgements This document was prepared with contributions from: • Martin Read, Gwyn Jones, Victor Abbott, Janet Burroughs, Amelie Thebault, Elizabeth Swann and Dave Uren from the University of Plymouth • Kimberly Monk and Ashley Gould, University of Bristol • Sabine Muller and Jens Lowag, Innomar Technologie GmbH • Richard Read and Paul Lawrence, Flagship Training, HMS Drake • Dr. Mark Redknap, National Museum of Wales • Nigel Boston, Geosa Ltd • GSE Rentals Ltd. • Captain Bob Stewart, Hydrographer of the Navy • Martin Dean and Mark Lawrence, ADUS • Kevin Camidge, CISMAS 2 Geophysical Investigations of the Cattewater Wreck 1997-2007 Contents Introduction ................................................................................................................................ 5 Scope ..................................................................................................................................... 5 The Cattewater....................................................................................................................... 5 The Cattewater Wreck ........................................................................................................... 7 Environment ........................................................................................................................... 8 Coordinate Frame ................................................................................................................ 10 Survey List ........................................................................................................................... 10 S u r v e y s .................................................................................................................................... 11 1997 Geophysical Survey (Potten) ...................................................................................... 11 2005 MBES Survey (Dean) .................................................................................................. 14 2006 MBES Survey (Bolton) ................................................................................................ 15 2006 SBP Survey (Thebault) ............................................................................................... 17 2007 Survey (Swann) .......................................................................................................... 22 2007 HiRes Magnetometer Survey (Holt) ............................................................................ 27 2007 MBES Survey (RN) ..................................................................................................... 30 Discussion ............................................................................................................................... 32 Data Processing ................................................................................................................... 32 Target Groups ...................................................................................................................... 33 Cattewater Wreck Position ................................................................................................... 34 Cattewater Wreck Site ......................................................................................................... 35 Seabed Sediment ................................................................................................................ 35 Target Detection................................................................................................................... 36 Conclusions ............................................................................................................................. 39 General ................................................................................................................................ 39 Further Work ........................................................................................................................ 39 References and Bibliography .................................................................................................. 41 Sponsors .................................................................................................................................. 43 List of Figures Figure 1: Cattewater location ..................................................................................................... 5 Figure 2: Seabed bathymetry in the Cattewater ........................................................................ 8 Figure 3: Survey vessel Catfish ............................................................................................... 11 Figure 4: 1997 Potten Plate 12 ................................................................................................ 12 Figure 5: 1997 Potten Plate 13 ................................................................................................ 13 Figure 6: 2006 MBES survey runlines ..................................................................................... 15 Figure 7: 2006 Innomar SES-2000 SBP surface unit .............................................................. 17 Figure 8: 2006 Innomar SBP tracklines ................................................................................... 18 Figure 9: 2006 Sub-bottom profiler targets .............................................................................. 19 Figure 10: Target 06 F72a 100 kHz trace ............................................................................... 20 Figure 11: Target 06 F72a 12 kHz trace ................................................................................. 21 Figure 12: 2007 Sidescan sonar mosaic ................................................................................. 23 Figure 13: 2007 Magnetometer tracklines ............................................................................... 23 Figure 14: 2007 Magnetometer and sidescan targets ............................................................. 24 Figure 15: 2007 Rigging for the HiRes magnetometer survey ................................................ 27 Figure 16: 2007 HiRes magnetometer tracklines .................................................................... 28 Figure 17: 2007 RN Multibeam bathymetry image .................................................................. 30 Figure 18: Site Recorder showing Cattewater targets............................................................. 32 Figure 19: Target groups ......................................................................................................... 33 Figure 20: New estimated location for the hull ........................................................................ 34 Figure 21: Run 11B 100kHz (L) 12kHz (R) ............................................................................. 36 Figure 22: Run 13B 100kHz (L) 12kHz (R) ............................................................................. 37 Figure 23: Run 3B 100kHz (L) 12kHz (R) ............................................................................... 37 Figure 24: Run 7A 100kHz (L) 12kHz (R) ............................................................................... 37 3 Geophysical Investigations of the Cattewater Wreck 1997-2007 Abbreviations GPS Global Positioning System LAT Lowest Astronomical Tide MBES Multibeam echo sounder OSGB36 Ordnance Survey of Great Britain 1936 reference frame RN Royal Navy SBP Sub-bottom profiling sonar TIFF Tagged Image File Format UTM Universal Transverse Mercator projection WGS84 World Geodetic System 1984 reference frame 4 Geophysical Investigations of the Cattewater Wreck 1997-2007 Introduction Scope This document describes the geophysical surveys undertaken on the site of the Cattewater wreck in the lower reaches of the Plym River, Plymouth, UK, between 1997 and 2007. The work is part of a long-term project to collect geophysical data and use it to help locate shipwrecks and other cultural remains within Plymouth Sound and its estuaries. The Cattewater The Cattewater is the name given to the lower reaches of the River Plym, the river associated with the City of Plymouth in South West England. The Plym starts on the high ground of Dartmoor to the north-east and drains into the waters of Plymouth Sound at its north-east corner through a drowned river valley or ria. In times of a much lower sea-level, the deep-cut limestone gorge at the mouth of the River Plym met with the deep-cut limestone gorge at the mouth of the River Tamar to the west, before the confluence then