This format is used for over 4 million surface current observations obtained by the ship drift method. Date, data source, position, (not latitude-longitude, but geographic grid numbers to six-minute by six-minute squares), and current direction and speed are recorded for each observation. With the exception of about 5,100 observations taken using the Geomagnetic Electrokinetograph (GEK), these are not instrument-measured current data. Rather, they are indirect determinations of ocean surface currents based on the ship drift method. In this method, the difference between a ship's dead- reckoned position (determined from its previous position, speed, and heading) and actual position determined from a navigational fix is ascribed solely to the effect of surface currents.
One 40-character record
| PARAMETER | DESCRIPTION | STARTING COLUMN | FIELD LENGTH |
|---|---|---|---|
| FILE NUMBER | ALWAYS '7' | 1 | 1 |
| DATA SOURCE | TWO-DIGIT CODE - (0=U.S., 1=NETHERLANDS, 2=JAPAN 3=U.S. SUBMARINE LOGS, 4=BRITAIN, 5=FRANCE, 6= JAPANESE GEOMAGNETIC ELECTROKINETOGRAPH (GEK), 15=NETHERLANDS AND LESS THAN 1% JAPAN, WITH YEAR, DAY, AND 6-MINUTE POSITION NOT RECORDED) | 2 | 2 |
| DATE(GMT) | YYYMMDD - YEAR, MONTH, DAY (YEAR<100 = 19TH CENTURY; YEAR>or=100 = 20TH CENTURY; 255 = NOT RECORDED - E.G. YEAR 1925 CODED AS '125' AND YEAR 1887 CODED AS '87') | 4 | 7 |
| AREA | ONE-DIGIT CODE (1=NORTH ATLANTIC, 2=OTHER OCEAN AREA) | 11 | 1 |
| TEN-DEGREE SQUARE | MODIFIED CANADIAN TEN-DEGREE SQUARE NUMBER | 12 | 4 |
| FIVE-DEGREE SQUARE | MODIFIED CANADIAN FIVE-DEGREE SQUARE NUMBER | 16 | 1 |
| TWO-DEGREE SQUARE | MODIFIED CANADIAN TWO-DEGREE SQUARE NUMBER | 17 | 2 |
| ONE-DEGREE SQUARE | MODIFIED CANADIAN ONE-DEGREE SQUARE NUMBER | 19 | 2 |
| QUARTER OF ONE- DEGREE SQUARE | MODIFIED CANADIAN 'QUARTER DEGREE' SQUARE NUMBER (= 1,2,3, OR 4; 9=NOT RECORDED) | 21 | 1 |
| SIX-MINUTE SQUARE | MODIFIED CANADIAN 'ONE-TENTH DEGREE SQUARE' NUMBER (=00 THROUGH 99; 100=NOT RECORDED) | 22 | 3 |
| CURRENT DIRECTION | XXXXXXXX (TENS OF DEGREES; 36 COMPASS POINTS) | 25 | 8 |
| CURRENT SPEED | XXXXXXXX (KNOTS TO TENTHS) | 33 | 8 |