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Satellite Ship Weather Tiny

Introduction/Additional information: 

The Satellite Ship Weather Tiny message is intended to be used to transmit weather observations over ship that will be received by Satellite AIS receivers. The difference between this message and the DAC 1 FI 21 Ship Weather report is that this message has been reduced in size to provide increased probability of detection via satellite. Similar to the rationale for the AIS message 27, this message is much less than a single slot.

All directions are relative to True North, all positions are WGS-84 Datum.

  1. For this message, the data is assumed to be from transmitting MMSI, and is a ship station. The sensor owner is the source of the data, as indicated by the MMSI. The data is assumed to be raw real time data with a validity interval of 6 hours.
  2. In order to reduce sentence size while retaining weather data, the position has been dropped from this message so the position of the data report must be inferred from the AIS message 27s or 1s received around this message.
Permitted as from: 
01/10/2019
Registrant: 
USACE
Physical link: 
AIS
Message number (0=VDES-VDE): 
8
DAC or VPFI: 
367
FI / Message ID: 
25
Version: 
0
Technical point of contact: 

Dr. Gregory Johnson

State: 
draft
State link: 
Weather observation report from ship
Number of slots (max): 
1
Last modified: 
02/03/2021 - 14:00
Reporting Rate: 

Current testing has used a reporting interval of 3 minutes

Used by: 
USACE
MARAD
NOAA
Details: 

Parameter

# of bits

Description

Standard Message Header

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. (See ITU-R M.1371-3, Annex 2, § 4.6.1).

0 – 3; 0 = default; 3 = do not repeat any more. Set to 0 (default).

Source MMSI

30

MMSI number of source station.

Spare

2

Not to be used. Set to zero.

Binary Data

Designated Area Code

10

Designated area code (DAC). (See Rec. ITU-R M.1371-3 § 2.1, Annex 5). Set to 367 (US).

Function Identifier

6

Function identifier. Set to 25.

Application Data

Version

3

Sequential number used to indicate the message version in steps of 1.

0 = test message = default; 1 – 7 = message version.  Set to 0.

UTC hour

5

UTC hour of the time of the data.

0 – 23; 24 = UTC hour not available = default;
25 - 31 (reserved for future use).

UTC minute

6

UTC minute of the time of the data.

0 – 59; 60 = UTC minute not available = default;
61 - 63 (reserved for future use).

Air Pressure

9

Air pressure, defined as pressure reduced to sea level, in 1 hPa increments.

0 = pressure <800 hPa; 1 - 401 = 800 – 1200 hPa;
402 = pressure of 1201 hPa or greater;
403  = data unavailable = default;
404-510 = reserved; 511 = not to be used[GJ1] .

Wind Speed

7

Average of wind speed values over the last 10 minutes in 1 knot increments.

0 - 120 knots; 121 = wind 121 knots or greater; 122 = data unavailable = default; 123 – 126 = reserved; 127 = not to be used.

Wind Direction

9

Direction of the average wind over the last 10 minutes in 1 degree increments.

0 – 359 degrees; 360 = not available = default; 361 - 510 = reserved; 511 = not to be used[GJ2] .

Spare

1

Set to zero.

Total bits

96

<1 slot message

 [GJ1]NOAA VOS wants pressure to the tenth – this would need 3 more bits

 

Or would bits be better used for tendency?

 [GJ2]NOAA VOS only records wind in 10 degree increments so could save 3 bits here

How portrayed: 

Display on an ECS the same as other weather information; however, this message is intended for the transmission of weather data from ship to shore (via satellite).

Attachment: 
PDF icon ssw_tiny_fi25_release_0-8apr19.pdf