Location Devices

Location, location, location is all important to safety at sea.

Positional devices can be broadly divided into two categories:

1. Tracking, monitoring, search and rescue
2. Collision avoidance

1. Tracking, monitoring, search and rescue

   Global Positioning System technology, also known as GPS, is the main source of identifying and/or monitoring the whereabouts of yachts and their crew all over the world's oceans.

   GPS is a satellite navigation system which determines the position of a yacht or a member of crew anywhere in the world. The system consists of 24 evenly spaced satellites which orbit the earth once every 12 hours at high speed resulting in direct line-of-sight to four of those satellites at any one time from anywhere on the globe. Each satellite broadcasts a signal that includes current position, orbit, and exact time. A GPS receiver triangulates the signals from a minimum three, optimum four satellites to determine the receiver's position with extraordinary accuracy. Even allowing for satellite geometry, signal blockage and atmospheric conditions, most GPS receivers can attain results to within a 100metre radius.

   How do EPIRBs and PLBs work ?

   EPIRBs and PLBs use Global Positioning System technology to pinpoint the exact position of a yacht or individual in distress.

   EPIRB stands for Emergency Position Indicating Radio Beacon - PLB stands for Personal Locator Beacon.

   EPIRBs and PLBs transmit their emergency signals on the 406MHz distress frequency via the free to use, multi-national Cospas Sarsat network.

   PLBs can also have LAS (Local Area System) capability which transmits a homing signal on 121.5MHz to the Search and Rescue services e.g. ACR ResQlink View 

   Optional Extra Transmission Channels:

   • VHF DSC (very high frequency, digital selective calling) - DSC is the standard for transmitting pre-defined digital messages.
   • AIS (Automatic Identification System) VHF frequency.

   Jimmy Green offer the McMurdo G8 AIS Smartfind EPIRB which transmits a man overboard alarm alert on AIS VHF frequency to any AIS enabled vessel up to four nautical miles, dependent on sea state and aerial height.

   EPIRB and PLB Comparison Table:

   Device	Registration	Application	Activation	Battery Life	Buoyancy
   PLB	Registered to an individual	Outdoor on land and sea	Manual activation	minimum 24 hours	Some float, some require a buoyant pouch
   EPIRB	Registered to a vessel	at sea only	Manual or automatic activation	minimum 48 hours	All EPIRBs float

   Close Range Man Overboard Recovery Capability may prove the difference between a successful rescue or a fatal catastrophe. Homing in on a casualty in the water can be achieved via AIS or GPS:

   AIS Beacons are manually activated location devices which transmit the man overboard location to any yacht or ship's chart plotter up to four nautical miles, dependent on sea state and aerial height

   OLAS stands for Overboard Location Alert System which uses Bluetooth, mobile app technology and GPS to sound the man overboard alarm and help the remaining crew onboard to navigate a yacht back to the casualty.

2. Collision Avoidance

   There are thre main navigational aids to avoiding collision at sea:

   • AIS (Automatic Identification System) transmits and receives a yacht or ship's position, course and speed at frequent, regular intervals using VHF radio technology. N.B. Some yachts may have AIS units that receive, but do not transmit.
   • Radar Reflectors, positioned as high as possible on a yacht, will maximise their visibility to ships or yachts within radar range.
   • Radar