| Parameter | No. of bits | Description |
|---|---|---|
| Message ID | 6 | Identifier for Message 8; always 8. |
| Repeat Indicator | 2 | Used by the repeater to indicate how many times a message has been repeated. 0 - 3 0 = default 3 = do not repeat anymore |
| Source ID | 30 | MMSI number of source station. |
| Spare | 2 | Not used. Set to zero. |
| IAI | 16 | DAC = 001; FI = 31 |
| Longitude | 25 | Longitude in 1/1,000 min, ±180 degrees as per 2's complement (East = positive, West = negative). 181 = not available = default |
| Latitude | 24 | Latitude in 1/1,000 min, ±90 degrees as per 2's complement (North = positive, South = negative). 91 = not available = default |
| Position Accuracy | 1 | 1 = high (<10 m; Differential Mode of, e.g., DGNSS receiver) 0 = low (>10 m; Autonomous Mode of, e.g., GNSS receiver or of other electronic position fixing device) default = 0 |
| Time Stamp | UTC date and time of the data. | |
| UTC Day | 5 | 1 - 31 0 = not available = default |
| UTC Hour | 5 | 0 - 23 24 = not available = default |
| UTC Minute | 6 | 0 - 59 60 = not available = default |
| Average Wind Speed | 7 | Average of wind speed values for the last 10 minutes, in 1 knot steps. 0 - 125 knots 126 = wind 126 knots or greater 127 = not available = default |
| Wind Gust | 7 | Maximum wind speed reading during the last 10 minutes, in 1 knot steps. 0 - 125 knots 126 = wind 126 knots or greater 127 = not available = default |
| Wind Direction | 9 | Direction of the average wind during the last 10 minutes, in 1 degree steps. 0 - 359 degrees 360 = not available = default 361 - 511 (reserved for future use) |
| Wind Gust Direction | 9 | Direction of the maximum wind during the last 10 minutes, in 1 degree steps. 0 - 359 degrees 360 = not available = default 361 - 511 (not for use) |
| Air Temperature | 11 | Dry bulb temperature in degrees Celsius (as per 2's complement), in 0.1 degree steps. -60 to +60 degrees Celsius 601 - 1,023 (reserved for future use) -1,024 = data not available = default -1,023 to -601 (reserved for future use) |
| Relative Humidity | 7 | Relative Humidity, in 1% steps. 0 - 100% 101 = not available = default 102 -127 (reserved for future use) |
| Dew Point | 10 | Dew point temperature in degrees Celsius (as per 2's complement), in 0.1 degree steps. -20.0 to +50.0 degrees 501 = not available = default 502 - 511 (reserved for future use) -511 to -201 (reserved for future use) |
| Air Pressure | 9 | Air pressure, defined as pressure reduced to sea level, in 1 hPa steps. 0 = pressure 799 hPa or less 1 - 401 = 800 - 1200 hPa 402 = pressure 1201 hPa or greater 403 - 510 (reserved for future use) 511 = not available = default |
| Air Pressure Tendency | 2 | 0 = steady 1 = decreasing 2 = increasing 3 = not available = default |
| Horizontal Visibility | 8 | Horizontal visibility, in 0.1 Nautical Miles steps (00000000 to 01111111). 0.0 - 12.6 Nautical Miles The most significant bit (MSB) indicates that the maximum range of the visibility equipment was reached and the reading shall be regarded as > x.x NM. (e.g., if 10110010, then visibility is 5.0 NM or greater) 127 = data not available = default |
| Water level (incl. tide) | 12 | Deviation from local chart datum, in 0.01 metre steps. -10.0 to +30.0 metres A value representing 0 - 4,000 is sent by the 12 binary bits. The water level is achieved by adding -10.0 to the sent value. Water level = (Integer value /100) – 10 for Integer = 0-4,000 4,001 = not available = default 4,002 – 4,095 (reserved for future use) |
| Water Level Trend | 2 | 0 = steady 1 = decreasing 2 = increasing 3 = not available = default |
| Surface Current Speed (incl. tide) | 8 | Speed of Current measured at the sea surface, in 0.1 knot steps. 0.0 - 25.0 knots 251 = speed 25.1 knots or greater 255 = not available = default 252-254 (reserved for future use) |
| Surface Current Direction | 9 | Direction of Current at the sea surface, in 1 degree steps. 0 - 359 degrees 360 = not available = default 361 - 511 (reserved for future use) |
| Current Speed, #2 | 8 | Speed of Current 2 measured at a chosen level below the sea surface, in 0.1 knot steps. (Same as Surface Current Speed) |
| Current Direction, #2 | 9 | Direction of Current 2, in 1 degree steps. (Same as Surface Current Direction) |
| Current Measuring level, #2 | 5 | Measuring level below sea surface, in 1 metre increment. 0 - 30 metres 31 = not available = default |
| Current Speed, #3 | 8 | Speed of Current 3 measured at a chosen level below the sea surface, in 0.1 knot steps. (Same as Surface Current Speed) |
| Current Direction, #3 | 9 | Direction of Current 3, in 1 degree steps. (Same as Surface Current Direction) |
| Current Measuring level, #3 | 5 | Measuring level below sea surface, in 1 metre steps. 0 - 30 metres 31 = data not available = default |
| Significant Wave Height | 8 | Height of the waves, in 0.1 metre steps. 0.0 - 25.0 metres 251 = height 25.1 metres or greater 255 = data not available = default 252 - 254 (reserved for future use) |
| Wave Period | 6 | Wave period, in 1 second steps. 0 - 60 seconds 61 - 62 (reserved for future use) 63 = not available = default |
| Wave Direction | 9 | Direction of waves, in 1 degree steps. 0 - 359 degrees 360 = data not available = default 361 - 511 (reserved for future use) |
| Swell Height | 8 | Height of the swell, in 0.1 metre steps. 0.0 - 25.0 metres 251 = height 25.1 metres or greater 255 = data not available = default 252 - 254 (reserved for future use) |
| Swell Period | 6 | Swell period, in 1 second steps. 0 - 60 seconds 61 - 62 (reserved for future use) 63 = not available = default |
| Swell Direction | 9 | Direction of swells, in 1 degree steps. 0 - 359 degrees 360 = not available = default 361 - 511 (reserved for future use) |
| Sea State | 4 | Beaufort Scale, as defined in Table 1.2 (below) |
| Water Temperature | 10 | Temperature of the water in degrees Celsius (as per 2's complement), in 0.1 degree steps. -10.0 to +50.0 degrees 501 = data not available = default 502 - 511 (reserved for future use) -511 to -101 (reserved for future use) |
| Precipitation (type) | 3 | According to WMO 306 Code table 4.201: 0 = reserved 1 = rain 2 = thunderstorm 3 = freezing rain 4 = mixed/ice 5 = snow 6 = reserved 7 = not available = default |
| Salinity | 9 | Salinity, in 0.1‰ (ppt) steps. 0.0 - 50.0 ‰ 50.1 = salinity 50.1 ‰ or greater 510 = not available = default 511 = sensor not available 502 - 509 (reserved for future use) |
| Ice | 2 | 0 = No 1 = Yes 2 = (reserved for future use) 3 = not available = default |
| Spare | 10 | Not used. Set to zero |
| Total | 360 | Occupies 2 slots |
| Sea Conditions | |
| 0 | Flat. |
| 1 | Ripples without crests. |
| 2 | Small wavelets. Crests of glassy appearance, not breaking. |
| 3 | Large wavelets. Crests begin to break; scattered whitecaps. |
| 4 | Small waves. |
| 5 | Moderate (1.2 m) longer waves. Some foam and spray. |
| 6 | Large waves with foam crests and some spray. |
| 7 | Sea heaps up and foam begins to streak. |
| 8 | Moderately high waves with breaking crests forming spindrift. Streaks of foam. |
| 9 | High waves (6-7 m) with dense foam. Wave crests start to roll over. Considerable spray. |
| 10 | Very high waves. The sea surface is white and there is considerable tumbling. Visibility is reduced. |
| 11 | Exceptionally high waves. |
| 12 | Huge waves. Air filled with foam and spray. Sea completely white with driving spray. Visibility greatly reduced. |
| 13 | not available = default |
| 14 - 15 | (reserved for future use) |