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This page compares the features of COSPAS / SARSAT with Inmarsat-E EPIRBs like the navtec global-3. Please see also the technical data overview of the different systems and the summary of the used abreviations.
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System comparison COSPAS/SARSAT with Inmarsat-E
 
Inmarsat-E like the global-3 EPIRB
COSPAS/SARSAT type EPIRBs
In operation since ... Jan 1997, system designers learned from faults and omissions of other systems in the past. 1982
Registration Programming No Programming required, only a fax to Inmarsat / London for registration. Changes are free of charge. Time consuming and costly programming of the beacon is required
Type of satellite Geostationary satellites allow for fast alerting, because the satellites are always visible Low earth orbiting satellites (LEO)
Time between activation and recognition at RCC Typical time for reception of distress call at RCC is under 3 minutes after transmission.  Depending on the satellite geometry. Minutes possible, but in average hours.
Position accuracy Within 113 m up to 20-NM, without GPS
Position finding
  • Built in GPS.
  • No external connection necessary.
  • No external power necessary.
  • Automatic position update with every transmission within 48 hours.
  • Less expensive units use the effect of Doppler shift. 
  • Two satellite passes are necessary to resolve the system ambiguity.
  • More expensive units use a connected or built in GPS.
Number of usable transmission channels / frequencies 667 channels (!) capacity for future expansion and redundancy 1 single channel (two since 2002), possibly overloaded in case of several ships transmitting in a (large) common geographic area 
Type of modulation Highly redundant and repetitive signal for 5 minute periods with extensive forward error correction. Even waves can wash over the unit without deteriorating the signal (!) Single data burst every 50 seconds with no further redundancy.
Antenna diagrams





Omnidirectional Antennas, RHCP polarisation, 
 

  • Radiation pattern of an Inmarsat-E an-tenna (global-3 EPIRB). The radiation is hemispherical. Even if the EPIRB is tilted in waves it radiates to the horizon.
  • No polarisation loss, because both EPIRB and satellite use circular polarisation

Vertical polarised antennas in all COSPAS/SARSAT beacons.

  • Radiation pattern of a Laymbda/4 wire antenna. No radiation towards zenith. Rubber Duck antennas are even poorer.
  • Additional -3 dB polarisation loss from the vertical polarised EPIRB to the circular polarised satellite.
False alerts No equipment generated false alert has ever been noticed. The design prevents false alarms. 1000 false alarms on every actual emergency on 121,5-MHz and 8 false alarms on every actual emergency on 406-MHz
Use of fast geostationary satellites Inmarsat achieves the reliability of the system with redundant satellites. Better then 99,9 % availability. The promised geostationary satellites are not yet operative. If they are operative, there will be a large gap in Central Europe
Type approval The global-3 EPIRB is fully type approved for SOLAS (GMDSS) Therefore it can be used on any vessel. Many units are for non-GMDSS use only. Please check first.
Remote Control Unit (RCU) Available. Nature of distress can be entered. Position on Display and NMEA out. RCUs are usually not available
Piracy & man overboard Software option already built in (!) update possible, if cleared by IMO No such provisions
Requirements on Ships > 300 grt. 1 x EPIRB with RCU is sufficient

(SOLAS, Chptr. IV, Rule 7, 1.6.2 ... 1.6.5)

2 x EPIRB without RCU are mandatory
Activation and transmission in Cradle With Inmarsat beacons useful and possible Usually impossible
Cancellation of an alert  To allow for cancellation of accidental activation of the EPIRB there is a short waiting period and an audible alert before transmission No such provisions
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Please see also the technical data overview of the different systems and the used abreviations.