0 0 RESERVED
1 1 MANUAL READING FROM VERTICAL TIDE STAFF
2 2 MANUAL READING FROM SINGLE AUTOMATIC RECORDER AT STATION
3 3 MANUAL READING FROM MULTIPLE AUTOMATIC RECORDERS AT STATION
4 4 AUTOMATIC READING FROM SINGLE AUTOMATIC RECORDER AT STATIONWITHOUT LEVEL REFERENCE CHECK.
5 5 AUTOMATIC READING FROM A SINGLE AUTOMATIC RECORDER AT STATION WITH LEVEL REFERENCE CHECK, OR FROM MULTIPLE AUTOMATIC RECORDERS.
6 6 RESERVED
7 7 MISSING VALUE
