Hyperbolic Anomaly
Definition
The characteristic arch shape that point-like or cylindrical subsurface targets produce on a radargram. As the antenna passes over a discrete reflector (pipe, bone cluster, grave edge), it picks up the target from a range of angles, creating the curved form. The apex marks the target's position.
- Shape
- Arch-like curve on the GPR radargram
- Cause
- Antenna detects a point reflector across a range of angles as it passes over
- Apex meaning
- Marks the target's true horizontal position and approximate depth
- Typical targets
- Pipes, bone clusters, grave edges, buried objects
Common questions
How does an operator turn a hyperbolic anomaly into a depth estimate?+
The curvature of the arch depends on the radar wave velocity through the soil, so software fits the hyperbola's shape against a velocity model, calibrated against a known reflector or a common-midpoint survey, to convert the apex position into a depth figure.
Can a hyperbolic anomaly be a false alarm rather than a real buried object?+
Yes, roots, rocks, utility lines, and soil layering discontinuities can all produce similar curved reflections, which is why GPR anomalies are treated as targets for further investigation rather than confirmed finds on their own.
Related terms
- Antenna Frequency
- The centre frequency of the radar pulse, typically expressed in megahertz. Higher frequencies give finer resolution but penetrate less deeply. Lower frequencies...
- Dielectric Permittivity
- A soil's capacity to store and transmit electric field energy. Higher water content raises permittivity and slows the radar wave. The contrast...
- Radargram
- The cross-sectional image produced by a GPR survey. The horizontal axis represents distance along the survey line; the vertical axis represents two-way...
- Two-Way Travel Time (TWT)
- The time from transmission of a pulse to receipt of its reflection. Depth is calculated as: depth = (velocity × TWT) /...
- Velocity Calibration
- The process of estimating the true electromagnetic wave velocity in the survey soil, usually by fitting a hyperbola to a known reflector...