Originally Posted by
terrymorse
I’m far from an expert on discrete signal processing, but isn’t the Nyquist rate (for periodic signals) a lower bounds for the sampling rate of non-periodic signals?
Nyquist rate is determined by the frequency content of the signal being sampled. CD's band limit the audio content to ~22 kHz before sampling at twice that rate. In some fields it is common to sample at a rate well below Nyquist than use multiple sample rates to resolve any ambiguities.
None of this explains what short cuts Garmin and others take in their GPS units. They have little processors that need to juggle multiple tasks. Sometimes things get dropped.