GMDSS(Global Maritime Distress and Safety System)

      GMDSS  ( Global Maritime Distress and Safety System )

In GMDSS there are different Sea areas to allot the working equipment in the respective areas.

they ate as follows

Area A1

Range - around 20 to 50 nm 

Equipment  - VHF 

CH 70 (156.525 MHZ) DSC

CH 16 (156.80 MHZ)R/T

Area A2

Range - 50 to 250 nm

Equipment - VHF,MF

(2187.5 KHZ)DSC

(2182 KHZ)R/T

(2174.5 KHZ) NBDP

Area A3

Range - 76 deg N to 76 deg S

Equipment - VHF, MF , SAT C

1.5 to 1.6 GHZ 

Area A4

Range - N of 76 deg N and S of 76 deg S 

Equipment - HF, MF, VHF 

GMDSS equipment power supply - 24 volt dc

except VHF - 10.5 to 13 volt dc 

Tests and checks 

daily 

1.internal non radiating DSC test 

use built in self test menu and carry out self test 

2. GMDSS reserve battery OFF/ON load voltage test 

off load 24V and on load 23.5 V 

3. check printer paper

weekly

1. radiation test

send DSC test call to coast station using MF or HF DSC

2. reserve power check battery 

monthly 

EPIRB , SART , GMDSS walkie talkie

GMDSS battery, antenna , emergency generator

( enter tests in GMDSS log ) 

Distress situations 

fire and explosion 

flooding

sinking

collision

grounding

listing

capsizing

piracy

man overboard

Urgency situations

propeller damage

engine failed 

steering damaged 

require tow (Maritime assistance)

Medical advice

evacuation of sick person ( medical assistance ) 

                                           SAT C 

Geo stationary satellites ( 36000km )

operates in 1.5 to 1.6 GHZ 

has space segment , ground segment , mobile earth station (MES) and land earth station (LES)

consists of four satellites 

AOR-E

AOR-W

IOR

POR

Enhanced group calling (EGC) receiver is incorporated in SAT C

ships navigating in sea area A3 and other area outside NAVTEX coverage , for reception of Maritime Safety Information

32 - Medical advice

38 - Medical assistance 

39 - Maritime  assistance

41 - Meterological report

42 - Navigational hazards

If NAVTEX not working the Nav area and Met area warnings can be send to SAT C through safety net service in EGC service

Advantage of SAT C = EGC service 

SAT C track 

ship earth station to sat = 1.6 GHZ

SAT to LES/CES   = 4 GHZ

LES/CES to SAT        = 6 GHZ

SAT to SES               = 1.5 GHZ

                                              NAVTEX

Is used to receive Maritime Safety Informations in coastal areas or navtex coverage areas

receiving frequencies

518 KHZ - in english 

490 KHZ - local language 

4209.5 KHZ - HF frequency

works when in coastal waters and up to 400 miles from shore 

made for all cargo ships of more than 300 GT 

receives by NBDP

Navtex stations and alloted stations are found in ALRS VOL 3 (1 & 2) , ALRS VOL 5

                                                EPIRB

works on the principle of doppler shift 

powered by 18 V lithium battery

when activated battery will be powering the EPIEB for 48 hours 

when activated strobe light flashes 20 to 23 times in min

EPIRB can be activated manually by removing the pin or as per manufactures instructions or by float free HRU

down link frequency to  LUT - 1544.5 MHZ

EPIRB track 

EPIRB - CASPAS SARSAT - LUT - MCC - RCC

transmitting power output of 5W

EPIRB signal 

406.025 MHZ 

121.5 MHZ  (homing signal for SAR aircraft)

EPIRB signal contains

 country code

15 digit hexadecimal beacon identification code 

contact no of owner 

                                                SART 

9 GHZ X band radar 

powered by 18 V lithium battery

SART on it will be on stand by mode for 96 hours

when it interrogates gives light and beep sound and battery will be 8 hours

as interrogated ship comes closer sound of beep is more 

detection range is 7 to 8 nm

12 dots equal spaced by about 0.64 nm

as craft approaches 2nm 12 dots changes to wide arcs 

arc changes to concentric circles as SART is close less than 1nm

before testing announce in VHF CH 16, set radar to 12nm

power transmission is 400mw

                                                    AIS

AIS system consists of  built in GPS or DGPS receiver , a VHF transmitter, two VHF receivers, VHF DSC modem , standard marine electronic communication link and sensor system

two types class A and class B 

operating voltage 24 V dc 

works in self organizing time division multiple access 

AIS transponder uses VHF frequencies 

AIS 1 (CH 87B) = 161.975 MHZ

AIS 2 ( CH 88B) = 162.025 MHZ

limitations of AIS

AIS operating on VHF range limited to 30 - 50 miles

non solas vessels cannot be picked by AIS

AIS is a transponder maximum 100 targets will be received by AIS

military ships have ability to shift off their AIS, then will not be able to pick up that target

Carriage requirements 

Class A mandatory for 300 GT and upwards on international voyage 

cargo ship of 500 GT and upwards not on international voyage 

passenger ships carrying more than 12 passengers 

                                                   LRIT

An automated position reporting system 

SAT C is being configured 

system consists of 

shipborne LRIT information transmitting equipment

communication service provider 

Application service provider

LRIT data center

LRIT data distribution plan

International LRIT data exchange

Access to LRIT 

flag state

coastal state

port state 

SAR organization

Guys do you got any doubt , comment me below

Good luck