Magnetometry

Date 23 March 2023 - 24 March 2023

Event ID 1171667

Category Recording

Type Magnetometry

Permalink http://canmore.org.uk/event/1171667

The cart-based gradiometer system used a Leica Captivate RTK GNSS instrument, which receives corrections from a network of reference stations operated by the Ordnance Survey (OS) and Leica Geosystems. Such instruments allow positions to be determined with a precision of 0.02 m in real-time and therefore exceeds European Archaeologiae Consilium recommendations (Schmidt et al. 2015). The detailed gradiometer survey was conducted using a non-magnetic cart fitted with four SenSys FGM650/3 magnetic gradiometers. The instrument has four sensor assemblies fixed horizontally 1 m apart allowing four traverses to be recorded simultaneously with an effective sensitivity of 0.03 nT over a ±100 nT range. Data was collected at 0.08 m intervals along transects spaced 1 m apart, in accordance with European Archaeologiae Consilium recommendations (Schmidt et al. 2015). Data was collected in the zigzag method. Ground Penetrating Radar The survey was conducted using an Impulse Radar Crossover 4080 system with a dual frequency antenna. The Crossover 4080 antenna is mounted on a rough terrain cart which is fitted with an odometer to measure horizontal distance along the ground surface. This was be deployed across the GPR areas within Cockenzie Harbour Wall East and the area south-west, with data collected along traverses spaced 0.5 m apart. Survey of the harbour wall produced evidence of an earlier construction phase of the harbour. The line of the earlier dock wall is denoted by a straight delineation in the data. The high amplitude point reflectors west of this line display the later construction phase during the remodel by Stevenson. The position of a former cottage may be highlighted within the eastern end of the harbour wall. While this corresponds with visible remains of the cottage, this response may be attributed more to water retention within the footprint of the former building. There is evidence of water retention at various depths in immediate vicinity of the southern and northern wall faces the in the wall. Part of these responses also coincides with the former position of a crane. Although not always clear, evidence for the potential tie wall locations have been identified within the data. These correspond to the plans produced by Stevenson during construction. The gradiometer survey areas have produced very limited evidence of possible archaeological activity associated with the Wagonway. This comprises a small rectilinear enclosure. Highly contrastive magnetic values impair further archaeological interpretation, possibly as a result of the industrial activity from the Wagonway coal industry through to the demolition of Cockenzie power station. The remaining anomalies are thought to be modern. These include demolition material, footpaths, services, and a garden feature identified in the Memorial Garden.

Information from OASIS ID: wessexar1-516869 (B Howard) 2023