A set of non‑invasive methods that measure contrasts in physical properties (magnetic susceptibility, electrical resistivity, ground conductivity, gravity, or dielectric permittivity) across an area to detect, map and prioritize buried archaeological features and subsurface anomalies.

Principle

Archaeological features alter the physical properties of the subsurface relative to the surrounding matrix; measuring spatial variations in those properties produces anomalies that can indicate the presence, extent or character of buried remains when interpreted against geological background and calibration data.

Demonstration

Situation: A planned excavation over a field with no visible features. Recognition: Magnetometry survey returns linear high‑amplitude anomalies aligned in a rectangular pattern. Action: Excavation targeted on the anomalies reveals masonry foundations corresponding to the survey pattern. Consequence: The survey reduced excavation area, revealed planimetric layout and improved resource allocation.

Misapplication

Attributing every detected anomaly to cultural activity without integrating geological checks, soil behaviour or ground‑truthing; the error is conflating anomaly presence with unequivocal archaeological significance.

Consequence

Geophysical survey can efficiently guide excavation strategy, limit destructive testing, and reveal large‑scale patterns; however, results are inherently interpretive and require calibration, method selection, and often ground‑truthing to avoid false positives or negatives.

Reversal

In uniformly magnetized, highly conductive or waterlogged substrates, some geophysical methods lose sensitivity or produce ambiguous results; conversely, certain features may produce no measurable contrast and remain invisible to specific techniques.

Boundary

Clearly within: magnetometry, electrical resistivity, ground conductivity and gravity surveys conducted to map subsurface contrasts. Boundary case: small‑area, high‑resolution prospection versus broad, low‑resolution regional surveys. Clearly outside: direct intrusive testing (trenching, coring), though these are used to validate geophysical interpretations.

Semantic Tension

Tension between coverage and resolution: methods offering rapid, large‑area coverage often trade spatial or depth resolution, while high‑resolution techniques require greater time or resources and smaller focus areas.

Synthesis

Geophysical survey translates physical contrasts into putative archaeological signatures; its value lies in efficiently focussing investigation, but reliable interpretation depends on appropriate method selection, contextual calibration and verification.