Page 153 - Green - Maritime Archaeology: A Technical Handbook. 2nd ed

132 Maritime Archaeology: A Technical Handbook, Second Edition
visibility, for example, more than 10 m, photogrammetric techniques would generally be used. Other acoustic systems include the PLSM Aqua Metre and MIT’s EXACT, which exist for general diver tracking (ecological surveys, search and rescue, etc.). The offshore oil industry has systems such as the Sonardyne Pharos system with accuracies around 20mm, al- though this system generally requires surface control. The following description is given of the use of the HPASS system on the Museum of Tropical Queensland 1999 Pandora expedition and on a project undertaken by the Rijksdienst voor het Oudheidkundig Bodemonderzoek (ROB) and The Netherlands Institute of Ship Archaeology (NISA) on the remains of a Roman bridge at Maastricht, The Netherlands.
The Pandora has been the responsibility of the Queensland Museum since 1983 and has been the subject of ten archaeological excavations (Gesner, 1993a,b; Gesner, 2000; Ward et al., 1998). Peter Gesner, the Pandora project director, invited the author, as part of Australian National Centre of Excellence in Maritime Archaeology, to assist in surveying the site using the newly developed HPASS system. The HMS Pandora was wrecked in 1791 while attempting a passage through the remote northern part of the Great Barrier Reef (latitude 11° 22.669S; longitude 143° 58.579E) carrying 10 prisoners from HMS Bounty to England for trial for their part in the “Bounty mutiny.” The site lies at a depth of about 31 m and the area is subject to unpredictable currents and, during the time of the expedition, a tidal range of 1.5 m. The 1999 expedition lasted from January 31 to February 28 and the HPASS system was used on a daily basis to survey the site. Data were processed in the field and used to record features on the site, excavation targets, and grid markers. At the end of the expedition a lengthy postexpedition data processing program took place, during which the manipulation of these data was refined and the software processing pro- grams were modified or changed. This provided a series of progressively more refined and more reliable results. This part of the report describes the site surveying process as well as the developments in the programming made in conjunction with Alec Duncan from the Centre for Marine Science and Technology (CMST) at Curtin University of Technology and with Peter Holt of 2H Surveying; and, finally, the results of the survey work with com- ments on the accuracy of the system.
In May 2000, Thijs Maarleveld and Arent Vos of NISA requested the CMST’s HPASS system to be used on a project consisting of a third century ad Roman bridge site in Maastricht, The Netherlands. This presented an opportunity to use the system on a site with poor visibility for which acoustic survey systems are ideally suited. The second part of this report describes work carried out by Souter who conducted all of the HPASS survey work in The Netherlands.