What gives them away is the crop itself: buried ditches and disturbed soils cause plants above them to grow at slightly different rates, producing faint stripes and shapes, known as cropmarks, that become legible only from the air.

Aerial photographs, referenced as GB89.P.31 and P.38, revealed an extensive field system at Rathbeagh defined by fosses, that is, shallow ditches or drainage channels, arranged in a mainly rectilinear pattern of right-angled boundaries. What makes the site particularly interesting is its close spatial relationship with a separate curvilinear enclosure nearby, a roughly circular or oval earthwork boundary of the kind often associated with early settlement or ritual use. The rectilinear field system and the curvilinear enclosure appear to belong to the same broader complex, suggesting organised land use across a substantial area at some point in the past. What complicates the picture further is that these cropmarks appear to be distinct from a different, relict field system shown on both the first edition Ordnance Survey map of 1839 and the revised edition of 1900. That later system is itself visible as cropmarks today, meaning two separate phases of field organisation are legible in the same ground, one documented in the nineteenth century and one apparently much older, each leaving its own faint signature in the soil.