National Maritime Electronics Association - NMEA Navtex Mesajları

Giriş

Navtex cihazını şu mesajlarla beslemek gerekir

GPS

RMC - Konum

ZDA - Saat ve Tarih

Navtex cihazından şu mesajlar okunur

1. ALR - Set Alarm State

Cihazdaki alarm durumunu belirtir

Mesaj şöyle

1. Sentence Id

2. Time of alarm condition change, UTC

3. Unique alarm number (identifier) at alarm source

4. Alarm's acknowledge state, A=Acknowledged,V=Unacknowledged

5. Alarm condition, A=Threshold exceeded, V=Notexceeded

6. Alarm description text

2. NRM - Navtex Receiver Mask Command

Mesaj şöyle. Hem input hem de output için kullanılabilir.

1. Sentence Id

2. Function code, 0 to 9

3. Frequency table index, 1 to 9

4. Transmitter coverage area mask

5. Message type mask

6. Sentence status flag, R or C

3. NRX - Navtex Received Message

Açıklaması şöyle

The NRX sentence is used to transfer the contents of a received NAVTEX message from the NAVTEXreceiver to another device. As the length of a single NAVTEX message may exceed the number of characters permitted in a single NMEA 0183 sentence, many NRX sentences may be required to transfer a single NAVTEX message.

Mesaj şöyle

1. Sentence Id

2. Total number of sentences, 001 to 999

3. Sentence number, 001 to 999

4. Sequential message id, 00 to 99

5. NAVTEX message code

6. Frequency table index, 0 to 9

7. UTC of receipt of message

8. Day, 1 to 31

9. Month, 1 to 12

10. Year

11. Total number of characters in this series of NRXsentences

12. Total number of bad characters

13. Status indication

14. Message body

4. alan olan Sequential Message Id için açıklama şöyle. Aslında 5. alan olan NAVTEX message code alanının kullanılmaması söyleniyor. Bu alan cümleleri birleştirirken kullanılıyor.

The sequential message identifier provides a unique identifier for each NAVTEX message represented by a group of sentences.

Though the message code contains a NAVTEX message serial number, there are special cases when the message serial number is set to 00 and has a different meaning or when the same message code can occur more than once. When these conditions occur, the sequential message identifier can be relied upon to uniquely identify this NAVTEX message from other NAVTEX messages with the same message code.

6. alan olan Frequency Table Index için açıklama şöyle

The frequency indicator identifies the frequency that the NAVTEX message was

received on:

0 = not received over air (eg test messages)

1 = 490 kHz

2 = 518 kHz

3 = 4209,5 kHz

4 through 9 are reserved for future use 

14. alan olan message body "c - c Calculated"  olarak işaretli. IEC 61162-1 Table 2'deki karakterlere göre çevrilmeli. Böylece her karakter için 1 byte harcanıyor

Örnek

Bir örnek şöyle. ^0D^0A "new line" demek. ^0A^0A mesaj sonu demek

The example below shows a typical message received by the Navtex receiver with 3 bad characters (‘*’):

<start of example>

ZCZC IE69==================================

ISSUED ON SATURDAY 06 JANUARY 2001.

INSHORE WATERS FORECAST TO 12 MILES

OFFSHORE FROM 1700 UT* TO 0500 UTC.

NORTH FORELAND TO SE**EY BILL.

12 HOURS FORECAST:

SHOWERY WINDS, STRONGEST IN NORTH.

NNNN

<end of example>

Inspecting the corresponding NRX sentences would typically show:

$CRNRX,007,001,00,IE69,1,135600,27,06,2001,241,3,A,==========================*09

$CRNRX,007,002,00,,,,,,,,,,========^0D^0AISSUED ON SATURDAY 06 JANUARY 2001.*29

$CRNRX,007,003,00,,,,,,,,,,^0D^0AINSHORE WATERS FORECAST TO 12 MILES^0D^0AOFF*0D

$CRNRX,007,004,00,,,,,,,,,,SHORE FROM 1700 UT^2A TO 0500 UTC.^0D^0A^0D^0ANORT*70

$CRNRX,007,005,00,,,,,,,,,,H FORELAND TO SE^2A^2AEY BILL.^0D^0A12 HOURS FOREC*16

$CRNRX,007,006,00,,,,,,,,,,AST:^0D^0A^0ASHOWERY WINDS^2C STRONGEST IN NORTH.^0D*15

$CRNRX,007,007,00,,,,,,,,,,^0A^0A*79

Decoding the message body should give the following result:

<start of decoding>

==================================

ISSUED ON SATURDAY 06 JANUARY 2001.

INSHORE WATERS FORECAST TO 12 MILES

OFFSHORE FROM 1700 UT* TO 0500 UTC.

NORTH FORELAND TO SE**EY BILL.

12 HOURS FORECAST:

SHOWERY WINDS, STRONGEST IN NORTH.

<end of decoding> 

Aynı örnek şöyle

$CRNRX,007,001,00,TD02,1,135600,27,06,2001,241,3,A,==========================*09

$CRNRX,007,002,00,,,,,,,,,,========^0D^0AISSUED ON SATURDAY 06 JANUARY 2001.*29

$CRNRX,007,003,00,,,,,,,,,,^0D^0AINSHORE WATERS FORECAST TO 12 MILES^0D^0AOFF*0D

$CRNRX,007,004,00,,,,,,,,,,SHORE FROM 1700 UTC TO 0500 UTC.^0D^0A^0D^0ANORT*70

$CRNRX,007,005,00,,,,,,,,,,H FORELAND TO SELSEY BILL.^0D^0A12 HOURS FOREC*16

$CRNRX,007,006,00,,,,,,,,,,AST:^0D^0A^0ASHOWERY WINDS, STRONGEST IN NORTH.^0D*15

$CRNRX,007,007,00,,,,,,,,,,^0A^0A*79