Latest evidence sweep: ninth confirmed; no tenth located
Reviewed 9 August 2026. The Bishopscourt evidence adds a ninth named, completed Isle of Man GPR survey context. A further sweep of IOMHER, Manx National Heritage, government and planning records, Tynwald material, research projects and general web results found no defensible tenth survey context. That is the status of the located public evidence, not proof that no other work has ever occurred.
- Lord Street planning file (2024): The later planning document repeats the June 2018 Lord Street survey already counted; it is not a second survey context. Isle of Man Planning Portal: Lord Street supporting document
- Unnamed brownfield scanner reference (2024): The Tynwald reference gives no site, survey date or report from which a distinct completed GPR survey context can be established. Tynwald: Environment and Infrastructure Policy Review Committee, 16 September 2024
- Port St Mary proposal (2024): The debate describes proposed work later represented by the already counted 2025 High Street completion, not a second survey context. Tynwald Court Hansard, 21 February 2024
Read a radar anomaly carefully
- GPR maps changes in reflected electromagnetic energy. An anomaly is not an artefact, wall, tunnel, grave or ‘treasure’ until tested against other evidence.
- A survey footprint is not an invitation to enter land. Some records are represented by a broad public area rather than a precise working grid.
- ‘Results unpublished’ means no public interpretation was located; it does not mean the survey found nothing.
Documented survey records
Tynwald Hill GPR Survey
Ground-penetrating radar was used within a wider programme of surveys at Tynwald Hill in 1993–96 and 2002.
Survey context: Archaeological
Public follow-up: No public follow-up established
Public results status: GPR use is confirmed. The preliminary interpretation is disputed by later summaries and does not demonstrate a prehistoric mound, burial or treasure.
Rushen Abbey GPR Survey
A Manx National Heritage-commissioned ground-penetrating radar survey was undertaken at Rushen Abbey in 1997.
Survey context: Archaeological
Public follow-up: No public follow-up established
Public results status: Survey confirmed; detailed results not published in the accessible catalogue.
The Ayres Coastal-Geology GPR
Published work includes a ground-penetrating-radar profile from The Ayres coastal foreland.
Survey context: Planning, engineering or geological
Public follow-up: No public follow-up established
Public results status: A published figure confirms an Ayres radar profile; the displayed map circle is only a named-landscape context.
Cronk Guckley / Berk Farm GPR Survey
GPR formed part of the Round Mounds investigation at Cronk Guckley before excavation at Berk Farm.
Survey context: Archaeological
Public follow-up: Excavation
Public results status: GPR interpretation followed by excavation; a stone ring was identified.
Archallagan Cairns GPR Survey
The Round Mounds project used GPR at the Archallagan cairns in September 2016.
Survey context: Archaeological
Public follow-up: No public follow-up established
Public results status: Method and survey confirmed; results not published in the cited field update.
Billown Quarry West GPR Survey
A 2017 Stratascan GPR investigation west of Billown Quarry assessed superficial deposit depth.
Survey context: Planning, engineering or geological
Public follow-up: No public follow-up established
Public results status: The planning assessment records the 2017 GPR investigation; no standalone detailed GPR report is linked here.
Lord Street, Douglas GPR Survey
A full GPR survey of about 0.52 hectares was completed at the former Lord Street bus-station site in June 2018.
Survey context: Planning, engineering or geological
Public follow-up: No public follow-up established
Public results status: Full contractor report filed; possible urban features are interpreted cautiously and none is established as treasure.
Bishopscourt GPR and Magnetometry Survey
SUMO used ground-penetrating radar and magnetometry in the Bishopscourt grounds in 2022; the associated archaeological evaluation compared some findings with geophysical anomalies.
Survey context: Archaeological
Public follow-up: Archaeological evaluation
Public results status: SUMO report 06360 is unpublished. Wessex report 260210.03 confirms the GPR and magnetometry and cautiously correlates some evaluation findings with geophysical anomalies without establishing that GPR alone identified them.
High Street, Port St Mary Engineering GPR
Government roadwork preparation in 2025 included a GPR survey intended to locate cellar boundaries and utilities on High Street.
Survey context: Planning, engineering or geological
Public follow-up: No public follow-up established
Public results status: Completed engineering survey and intended purpose confirmed; no segment, footprint or archaeological interpretation published.
Frequently confused with GPR
“Geophysics” is a family of techniques, not a synonym for radar. We explicitly excluded or relabelled these cases.
Speke Keeill (2006)
The documented techniques were magnetometry and electrical resistance. Those are geophysical methods, but they are not ground-penetrating radar.
Wessex Archaeology: Speke Keeill excavation and geophysical survey report
Billown prehistoric archaeology
The 2003 ISAP conference abstract Man’s landscapes revealed captions the Billown Quarry excavation-area survey as fluxgate gradiometry, not GPR. A separate 2017 Billown Quarry survey used GPR for geological and overburden questions; that later engineering work must not be cited as the method that discovered the prehistoric archaeology.
International Society for Archaeological Prospection 2003: Man’s landscapes revealed
Poortown / Giant’s Grave
The published survey used magnetometry, electromagnetic conductivity and earth resistance—not GPR—so it is not counted.
Oxford Archaeology: Giant’s Grave, Poortown geophysical survey report
LiDAR and aerial mapping
Airborne laser topography and aerial photography can reveal earthworks, but neither is GPR. They are retained as separate evidence types where relevant.
Bishopscourt magnetometry and LiDAR
Magnetometry and LiDAR formed part of the wider Bishopscourt investigation, but they are not counted as additional GPR survey contexts. The record counts the documented 2022 Bishopscourt programme once.
What the map does not claim
It does not infer tunnels, graves, walls or objects from an anomaly alone. It does not convert a survey centroid into an exact target, and it does not fill unpublished results with speculation.