Signal-to-Noise Ratio (SNR)
Definition
The ratio of anomaly amplitude to background variation. Pipes, cables, rocks, roots, and instrument drift all add noise. A target is detectable only when its anomaly exceeds the noise floor with sufficient confidence to justify excavation.
- Definition
- Ratio of anomaly amplitude to background variation
- Common noise sources
- Pipes, cables, rocks, roots, instrument drift
- Detection condition
- Anomaly must exceed the noise floor with sufficient confidence
- Forensic context
- Determines whether a geophysical anomaly justifies excavation
Common questions
Why can a real buried target still go undetected in a geophysical survey?+
If the target's physical contrast with the surrounding soil is weak, or if the site has many other buried objects like pipes and roots producing their own anomalies, the target signal can sit below or blend into the background noise, making it statistically indistinguishable from clutter even though it is genuinely present.
How does an SNR assessment influence the decision to excavate a suspected clandestine grave anomaly?+
A high-confidence anomaly, one whose amplitude clearly stands above the surrounding noise, justifies the time and resource cost of excavation, while a low-SNR anomaly close to the noise floor is more likely to be a false positive from natural or unrelated buried material, so investigators often prioritise higher-SNR targets first when resources are limited.
Related terms
- 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...
- Electrical Resistivity
- The resistance of a volume of soil to electrical current flow. Wet, clay-rich, or decomposing organic material has low resistivity. Dry sand...
- Magnetic Susceptibility
- A measure of how strongly a material is magnetised by an external field. Topsoil heated by fire or biological activity has elevated...
- Multi-Method Survey
- The deployment of two or more independent geophysical methods over the same search area. Anomalies confirmed by multiple methods carry higher confidence...
- Physical Contrast
- The difference in a measurable soil property (density, susceptibility, resistivity, permittivity) between a target and its surrounding host material. No contrast means...