Bronze Age logboat poses challenge for Trimble GPS

The discovery of a 3,000 year-old logboat on the south bank of the Tay Estuary provided an interesting measurement challenge for Perth and Kinross Heritage Trust (www.pkht.org.uk). In 2001, partially buried by inter-tidal sands and gravels, the prow of what became known as the Carpow logboat was spotted and reported by Scott McGuckin, a metal detectorist from Dundee. Carved from a single tree trunk, the boat was found to be around 9.25m long, 1m broad, and remarkably well preserved. Given the significance of the vessel and the evidence of damage by tides and the weather, it was decided that the boat should be lifted from the estuary.Prior to the lifting date set at August 2006, the boatâs exact dimensions and position had to be recorded along with location data taken from the surrounding estuary mudflats. Heritage Officer Sarah Winlow explains, âWe needed to accurately record points from the prow to the stern but working conditions on the intertidal site were very difficult and made a conventional archaeological survey incredibly hard. Half of the boat was buried below the mudflats and so the excavation was persistently waterlogged. The time and space available for recording the boat were very constricted as the excavation team and two water pumps were working constantly. Therefore the traditional methods of using a bulky dumpy level for height measurements and using offset measurements from a known baseline for positional data were not feasible. Following a phone call to KOREC, their representative suggested that Trimble SPS GPS with SCS 900 software would offer the perfect solution!" The Trimble GPS allowed Perth and Kinross Heritage Trust to quickly and easily collect data with cm accuracy. The system also allowed for height information to be recorded which will be used to calculate the angle at which the boat was lying. These calculations will be an integral part of the final excavation report.Location data will be added to the Historic Environment Record (HER), a database, linked to GIS, of all archaeological and historical sites, buildings and find spots in the Perth and Kinross area. The accuracy of this data is vital for subsequent study and for reference to other topographical and geographical data. Sarah concluded, âThe speed and accuracy at which the data could be recovered with the Trimble GPS was fantastic â it is spot on! Following our survey, the boat was successfully excavated and then floated downstream to the village of Newburgh where it was transported by lorry to the National Museums of Scotland for conservation.âAdditional information: The Carpow vessel is the 8th logboat to have been recovered from the Tay estuary, the rest found in the 19th century and generally dating to between 500BC and 1000AD. The estuary landscape at the time of the logboat would have been occupied by settlements consisting of handfuls of houses (known as roundhouses), with small fields and pockets of woodland spread across the landscape. The inhabitants of these small settlements would have spent most of their time farming, although they would have also taken advantage of the rich estuary environment. The impressive size and design of the logboat suggests that it may have been used for a variety of tasks. It could hold between 10 to 12 individuals at a time, and is likely to have ferried people and trade goods around the estuary. It may also have been used for hunting and fishing, or, given its size, as a symbol of status.All information kindly supplied by Sarah Winlow, Heritage Officer, Perth and Kinross Heritage Trust. All images copyright PKHTImage above: The Trimble system, pictured here with KORECâs Dave Dawson and PKHT's Sarah Winlow and Lindsay Farquharson, proved ideal for measuring in challenging conditions

Author: Lucy Hamilton

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