Site 379 - Geophysics Earth Resistance Survey Report - Heritage Non-intrusive Survey Reports Group 025

The survey was undertaken using a Geoscan Research RM15-D earth resistance meter configured in a parallel twin-probe array system with multiplexer allowing for two pairs of two parallel electrodes (four total) spaced 0.5m apart. One current and one potential electrode (the remote or static probes) are fixed firmly in the ground a set distance away from the area being surveyed. The second current and potential electrodes (the mobile probes) are mounted on a frame and are moved from one survey point to the next. Each time the mobile probes are inserted into the ground an electrical circuit is formed between the current electrodes and the potential gradient between the mobile and remote probes is measured and stored in the memory of the instrument. The survey area was divided into grids measuring 30m by 30m, established using a Trimble R10 RTK GNSS instrument. The Trimble R10 system receives corrections from a network allowing for a precision of 0.01m in real-time therefore exceeding the level of accuracy recommended by EAC guidelines. 4.4.4 The instruments logged each reading at 1m intervals on traverses 1m apart within each grid. The mobile probe spacing was 0.5m with the remote probes 20m apart and at least 20m away from the grid being surveyed. This probe spacing of 0.5m gives an approximate depth penetration of up to 1m for most archaeological features. The HS2 Ltd Phase 2a GWSI: HERDS document identifies that EEW Group 025 falls within two distinct Recognised Archaeological Zones (RAZ), specifically RAZ 31 and RAZ 32. These zones both lie outside site 379, however nearby site 380, approximately 500m to the west, is designated a RAZ for the preservation of buried remains and extant earthworks associated with the deserted medieval village (DMV) known as Godwynesleigh. At the time of survey, the majority of the site contained maize stalks and very dry ground and was unsuitable for survey. A trial area totalling c.0.3ha was surveyed along the northern boundary of the site. The survey recorded an amorphous area of higher resistance readings in the northern corner of the site likely natural in origin and a number of linear trend anomalies likely a result of modern ploughing. The limited scope of the survey restricts a more confident interpretation though it remains unlikely the limited number and types of anomalies identified in the survey could relate to the nearby DMV of Godwynesleigh.