Personal locater beacons – the good, the bad, the ugly
March 3, 2015
Over President's Weekend Kate Martrosova attempted to traverse the Presidential Range in New Hampshire's White Mountains. The weather deteriorated after her pre-dawn start, with 140 mph winds, sub-zero temperatures and chest deep snow. According to most reports, she was fairly experienced and was equipped with appropriate clothing and gear, including an emergency personal locator beacon (PLB).
Matrosova activated her PLB at 3:30 from somewhere between Mt. Adams and Mt. Monroe, only about 3 miles into the 15-20 mile trek. Rescue crews were not able to locate her body until the following day because of a number of factors, especially the weather. Reportedly, the PLB provided "inconsistent" location information. One official speculated that the PLB was adversely affected by the cold. Matrosova apparently died of exposure.
PLBs are not new technology. Their marine counterpart is the EPIRB, which has been in use for decades and is credited with over 30,000 lives saved. Land based PLBs were authorized by the FCC in 2003 after a successful trial period in Alaska.
When a PLB is activated in an emergency it sends a signal to the international COSPAS-SARSAT satellite array which contains equatorial high altitude geostationary satellites and low polar orbit satellites. These two types of satellites work differently, but by linking the data provide excellent worldwide coverage. From there, the signal data is routed to the Air Force Rescue Coordination Center (AFRCC) in Florida. If the signal location is in Colorado, the next step is notification of the Colorado Search and Rescue Board State Coordinator who is tasked with notifying the sheriff in the county where the coordinates are located. The sheriff would then activate local search and rescue resources. Once the AFRCC has the data, it normally takes less than 30 minutes to get the information to the local authorities.
The emergency signal sent to the satellite system depends on the type of PLB. All will send the specific beacon identifier number tied to an international data base. By registering their PLB, owners provide search and rescue with critical information including name, address, contact info and perhaps most importantly, emergency contact info. The first thing the authorities will do is call those numbers to verify the problem and perhaps get more information – travel plan, expected time of return, number in party.
A couple years ago we had a person who received a PLB as a gift. He thought it was an avalanche transceiver and so turned it on only while he was skiing at Berthoud or Guanella. Search and rescue teams were activated several times, but when the PLB was turned off the signal vanished. The gentleman was finally tracked down at a parking lot in Boulder after he forgot to turn the PLB off. If he had registered the unit a phone call would have alleviated the false alarms.
These basic PLBs generate location data incrementally – it takes several satellite "passes" to nail down a good location. The first notification may be very rough, only within a couple miles or even at two possible locations miles apart. This is first location is normally generated within 30-45 minutes of activation. As more satellites receive data the position can be narrowed down. Pinpointing can take several hours, and even then may be ambiguous. Location data can be corrupted by poor satellite reception caused by vegetation, landforms, orientation of the device and low battery power. Or if the PLB is moving.
Some PLBs will also send GPS coordinates that give rescuers precise location – like within the size of a football field. As with any GPS, satellite reception is critical so a location near cliffs, under trees or in a narrow canyon may not reach out. If the PLB has a clear view, the location data is sent to the AFRCC within 5 minutes.
All PLBs also send out a low watt homing signal which can be used by search and rescue to home in on the PLB with a handheld direction finder once they are in the vicinity.
Here are some key concepts to take away.
• PLBs work even where there is no cell phone coverage and no GPS satellite coverage.
• PLBs provide valuable safety net, but should not be relied on as 100 percent effective. In a perfect world, help is still hours away. If you are seriously injured, will you be able to activate the PLB?
• Proper use includes registering your PLB and ensuring that the batteries are fully charged. Leave a travel plan with your emergency contact.
• COSPAS-SARSAT coordinates take time and can be ambiguous, especially early on.
• For a bit more investment, the GPS enabled beacon transmits location information more quickly and accurately. A clear view of the sky is required.
• Most commercially available PLBs are rated for 24 hours at -4 degrees.
• Do not confuse PLBs with similar satellite messenger devices like the SPOT. They are also a valuable safety tool, but work somewhat differently.
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