A 3-digit mooring number is used to identify all files containing time-series data and is the key through which one can identify and (or) locate data records in the Woods Hole Science Center time-series data management system. Individual data files are labeled by 4-digit numbers: the first three digits being the mooring number, the last digit indicating vertical position of the instrument in the mooring. For example, 5541 identifies the topmost instrument on mooring 554, 5542 the next instrument down on mooring 554, etc. As data files are processed, additional identifiers are added to the four-digit identifier to indicate sensors, processing steps, and averaging. (See digital data files.)