1.7 1.7.1 76
Geophysical survey Aims and objectives
The objective of geophysical survey is to seek to determine the location of geophysical anomalies that may indicate any subsurface features of archaeological significance. The specific aim is to define the exact extent and detail the layout of known archaeological activity, to identify areas of hitherto unknown archaeological activity, and to guide subsequent phases of the archaeological assessment programme.
77
Typically, the results of the 100% geophysical survey would be used in order to microroute the 55m Preferred Onshore Cable Corridor within the current 75m Onshore Cable Corridor. This may not be possible in areas with significant existing constraints.
78 1.7.2 79
Geophysical survey would be carried out as far in advance of the construction phase as is permitted within land access agreements.
Conditions
Suitable plots within the 75m Onshore Cable Route would be subject to geophysical survey, i.e. where the following conditions apply:
•
• • •
• 80 1.7.3 81
The previous land use will not have resulted in wide scale disturbance (e.g. site of former quarry)
The topography suggests that archaeological remains could be present (e.g. steep slopes will not be surveyed)
The ground cover is suitable for survey (e.g. areas of high crop, woodland, scrub, and waterlogging will not be surveyed)
The onshore electrical transmission works will have a physical impact on archaeological horizons (e.g. the HDD areas will not be surveyed)
Landowner access is consented Plots suitable for geophysical survey are annotated on Figure 25.6.4. Methodology
The recommended geophysical approach is to deploy a Magnetic Survey. This technique measures the absolute value of the Earth’s magnetic field and is used to
Outline Written Scheme of Investigation: Archaeology and Cultural Heritage (Onshore) Rev 01
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