NAVTEX (Navigational text messages) is a system to deliver local weather reports and navigational warnings to ships operating in coastal areas. It is an international automated direct printing service for promulgation of navigational and meteorological warnings and urgent information to ships. It has been developed to provide low cost, simple and automated means of receiving maritime safety information on board ships at sea in coastal waters. The NAVTEX system automatically broadcasts localised Maritime Safety Information (MSI) using Radio Telex (also known as Narrow Band Direct Printing, or NBDP).The information transmitted may be relevant to all sizes and types of vessel and the selective message rejection feature ensures that every mariner can receive a safety information broadcast which is tailored to his particular needs. For this on board a vessel a corresponding NAVTEX receiver as a part of SOLAS requirement is installed.
The system came in force from 01 August 1993 as a part of SOLAS requirement and is mandatory for all vessels above 300GT engaged in international voyage. NAVTEX fulfils an integral role in the Global Maritime Distress and Safety System (GMDSS which has been developed by the International Maritime Organization (IMO) and contributes to safety at sea.
- PRINCIPLE OF NAVTEX TRANSMISSION
NAVTEX is a component of the IMO/IHO World Wide Navigational Warning Service (WWNWS) defined by IMO Assembly Resolution A.706 (17) as amended, and the WMO Manual on Marine Meteorological Services. The operational and technical characteristics of the NAVTEX are contained in Recommendations ITU –R.M. 540-2.
NAVTEX is broadcast worldwide on 518 kHz using a data mode called SITOR-B. Its 7 unit data with forward error correction (FEC) using 100 Baud 170 Hz Frequency Shift Keying (FSK), with the centre frequency .being 1700 Hz. The transmission is carried out every 4 hours for 10 minutes on time sharing basis. However urgent message covering contingencies can be transmitted any time on instructions from the National Authority. NAVTEX is also transmitted in local language at 490 kHz or 4209.5 kHz depending on the convenience of the local authority. The principal features of NAVTEX are
- The international NAVTEX service uses a single frequency with transmission from nominated stations within each NAVAREA/METAREA being arranged on a time sharing basis to reduce the risk of mutual interference. All necessary information is contained in each transmission. Similarly, broadcasts on other IMO coordinated frequencies are operated on a time sharing basis.
- The power of each transmitter is regulated so as to reduce the risk of mutual interference between transmitters with the same heading character in different parts of the world.
- A dedicated NAVTEX receiver which has the ability to select messages to be printed The concept of NAVTEX transmission is shown below:
Here the registered information provider provides the information to the Navtex Message Coordinator – NAVAREA Commander. Who in turn forwards the information to the transmitting stations who transmit the message on area in time sharing basis
- INDIAN NAVTEX SCENARIO
There are over 150 NAVTEX transmitters are operational on international frequency i.e. 518 kHz in the World. IN addition no of transmitters on local language are operational. Indian Ocean Region falls under NAVAREA VIII whose coordinator is the Chief Hydrographer to the Govt. of India. Details of NAVAREA are placed at Annex I.
DGLL has looked into the requirement of ESTABLISHMENT OF INDIAN NAVTEX CHAIN. Following seven locations have been identified for the service:
- Veraval (Gujarat)
- Vengrula Point (Maharasthra)
- Muttam Point (Tamilnadu)
- Porto Novo (Tamilnadu)
- Vakalpudi (Andhra Pradesh)
- Balasore (Orissa)
- Keating Point (Andaman & Nicobar Islands)
These locations have been identified mainly on account of uniform spread and availability of the land. It may be mentioned that the range of the NAVTEX Service will depend on the efficiency of antenna and therefore a state-of-the-art antenna system is required to be developed carefully. DGLL has sufficient land at these locations and therefore no difficulty in establishing the system is felt. However other infrastructures like technical building, quarters and antenna system are required to be developed.
The proposed system architecture is shown at Annexure II. The information received from input authorities like Naval Chart Depot, Indian Meteorological Department & DG Shipping will be collected at NAVTEX coordinating centre which is proposed to be co-located with National Data Centre (NDC) of the upcoming National AIS Network. The information thus collected will be routed on main hub of AIS Network to transmitting station.