To accurately reconstruct a signal, sample at twice the highest frequency present.
Nyquist and Shannon's result. Its everyday consequence is the wagon-wheel effect in film: the wheel appears to rotate backwards because the frame rate undersamples the rotation.
In practice
- A camera filming at 24 frames a second shows a wheel rotating backwards, because it is sampling below the rotation rate.
- A monthly metric on a process that varies weekly will report trends that are artefacts of the sampling interval.
- Further reading
- Wikipedia
- Subject
- Technology & Software
- Essay
- The curves, the limits and the laws of software