The distance between points at which measurements are taken or the time which elapses between measurements; it is equal to the traverse (or record) length divided by the number of stations (or samples). For example, a 250 m ground traverse with 25 stations along it has a sampling interval of 10 m; a wave-form might be sampled every two milliseconds, i.e. with a sampling interval of 2 ms (and a sampling frequency of 500 Hz).