> The system has two data reporting modes, standard and event. The system operates routinely in standard mode, in which four spot values (of the 15-s data) at 15-minute intervals of the estimated sea surface height are reported at scheduled transmission times. When the internal detection software (Mofjeld) identifies an event, the system ceases standard mode reporting and begins event mode transmissions. In event mode, 15-second values are transmitted during the initial few minutes, followed by 1-minute averages. Event mode messages also contain the time of the initial occurrence of the event. The system returns to standard transmission after 4 hours of 1-minute real-time transmissions if no further events are detected.
Edit. From this page: http://www.ndbc.noaa.gov/dart/dart.shtml
> The system has two data reporting modes, standard and event. The system operates routinely in standard mode, in which four spot values (of the 15-s data) at 15-minute intervals of the estimated sea surface height are reported at scheduled transmission times. When the internal detection software (Mofjeld) identifies an event, the system ceases standard mode reporting and begins event mode transmissions. In event mode, 15-second values are transmitted during the initial few minutes, followed by 1-minute averages. Event mode messages also contain the time of the initial occurrence of the event. The system returns to standard transmission after 4 hours of 1-minute real-time transmissions if no further events are detected.
The algorithm is described here: http://www.ndbc.noaa.gov/dart/algorithm.shtml