identify small perturbations that are caused by variations in the electromagnetic properties of the subsurface.
82
The survey would be undertaken in accordance with the 2008 English Heritage publication Geophysical Survey in Archaeological Field Evaluation, and Standard and Guidance for Archaeological Geophysical Survey (IfA 2011), and the Suffolk County Council document ‘Requirements for a Geophysical Survey 2011’.
Equipment Bartington G801-2 Dual Fluxgate Gradiometer 83 84
This is a non-contacting item of geophysical survey equipment. The Grad601 is operated by a single geophysical engineer and powered by rechargeable battery.
Pairs of Fluxgate magnetometers are mounted vertically and attached to a horizontal bar, to complete an ‘H’ shape frame, which is hand ported by the surveyor. The instrument console is mounted on the horizontal bar in front of the operator.
85
Data are collected as a series survey grids. Readings are recorded at set distance intervals along a number of parallel transects. Survey grids are combined at the processing stage to produce an image of the magnetic response of the survey area.
86
Sensitivity of the instrument is ~0.3nT, which is in line with the English Heritage guidelines
Leica 1200 series SmartRover GPS 87
This is a high precision GPS system used for recording and staking out the survey area / grid as required. The equipment is also used for recording the location of any features of interest. The GPS consists of a receiver antenna, and control console that attach to a survey staff. Removable rechargeable batteries power the unit. The 1200 series smart rover is able to record locations to accuracy greater than 0.05m, which exceeds the accuracy detailed in the English Heritage guidelines.
Survey 88
The Leica smart rover will be used to stakeout the working areas and grids. Wooden stakes or canes will be used, as appropriate to mark the edges of the survey area at the perimeter of fields and nodes of survey grids.
Outline Written Scheme of Investigation: Archaeology and Cultural Heritage (Onshore) Rev 01
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