Signal-to-Noise Ratio (SNR) is the ratio of the power of a desired signal to the power of background noise. High SNR indicates clear information transmission or capture; low SNR indicates interference or degradation.
Photography and Imaging
In digital imaging, SNR relates to the quality of data captured by camera sensors.
- RAW Data: Camera Raw files preserve unprocessed sensor data, maximizing available tonal range and SNR before compression artifacts degrade the signal.
- Noise Management: Low-light conditions reduce photon count (signal), lowering SNR and increasing digital noise. Post-processing involves recovering signal while suppressing noise, leveraging the high bit-depth of raw formats.
Electromagnetic Interference and Navigation
SNR is critical in radio frequency applications, such as GPS, where external interference can overwhelm the weak satellite signals.
- GPS Vulnerability: GPS signals arrive at Earth with extremely low power, resulting in marginal SNR. Intentional jamming raises the noise floor, effectively dropping SNR below the threshold required for signal acquisition.
- Recent Investigations: A significant drop in GPS SNR across Europe in 2024 was linked to widespread jamming events.
- See Europe-wide GPS Jamming Events: Satellite Source Investigation Summary for details on the satellite source investigation led by Prof. Todd Humphreys, which analyzed data from European monitoring stations to trace the interference origin.
Key Principles
- Decibel (dB) Measurement: SNR is often expressed in decibels. Positive dB indicates signal dominance; negative dB indicates noise dominance.
- Thresholds: Each system has a minimum SNR threshold for reliable operation. In photography, this determines shadow detail; in GPS, it determines positional accuracy or signal loss.