personal locator beacons

I just purchased an ACR AeroFix PLB with onboard GPS and (obviously) feel the safety it will provide to my and my family will be worth the investment. It is the real deal.

If a beacon signal is received, they will call the phone numbers associated with registered beacons to try to determine if it is a false alert. If it is not, or if that cannot be determined, rescue personnel will be sent to the location of the beacon. If the Beacon has an onboard GPS or has been uploaded with the location from an external GPS, rescue services will know your location almost immediately. A PLB with onboard GPS will wake up the GPS every 20 minutes to aquire a new location - this is partially to save battery power so the beacon and broadcast as long as possible. If the PLB does not have a GPS location, then it may take up to 90 minutes (depending on where you are in the world) for your location to be determined.

A GPS location error on a PLB is around 350-500 feet. Without a GPS location the location error is around 12.5 miles (which is still pretty good considering - at least they'll come looking for you and should be able to home in on your beacon).

The actual time to rescue depends on a lot of other factors too - weather, geography, local SAR procedures, transportation time, etc...

A PLB with onboard GPS provides:

>>A 406 MHz beacon which, if registered, tells SAR teams who you are and who to call to check for false alerts and/or to get additional information.

>>Two different methods of location determination: a GPS location which provides nearly instant locationing within about 350 feet to rescuers, and if the GPS cannot determine the location, a Doppler location obtained using Low Earth Orbiting satellites than can estimate your location within about 12.5 miles a location in the U.S. in under 45 minutes.

>>A low power 121.5 MHz homing beacon for local searches.

The best place to learn how they work and to see the results of fairly extensive independent testing is the Equipped To Survive Foundation's most recent 406 MHz GPS Enabled Emergency Beacon Evaluation, available at:

http://www.equipped.org/406_beacon_test2_toc.htm

They tested several different beacons under varying conditions to see if they would be "heard", if the GPS would provide a location, and how long it took to get the location and/or reaquire the location. See the Summary of Results tables.

That site's explanation of how the COSPAS-SARSAT system works and how GPS's work and interact with the PLB's is the most comprehsive explanation I'v been able to find.
 
Understand that these need to be able to "see" the sky to work. If you are in a canyon, or in densely wooded area (Pacific Northwest) then you will have a tough time getting a signal out. Even the SAT phones need lots of sky to acquire sat signals

IF you get a signal out, the SAR Teams, or Local Law Enforcement Officer will most likely be to you within 6-12 hours depending on your location and weather.

That said, the model you purchased is the real deal, using the latest, greatest technology. It should serve you well. I pray you NEVER need to use it.

Have a safe weekend!
 
Here is one of the conclusions from the ETS Foundation PLB testing:

"Results from the gorge test suggest that Doppler location can be achieved even with a very limited sky view, though it may take multiple LEO satellite passes. While it may be possible to acquire a GPS location if there is a fortuitous confluence of sufficient GPS satellites visible during a period of time while the GPS receiver is operational, this cannot be counted upon in such circumstances."

So even with limited view to the sky rescue crews will hear the beacon and will likely get a location, though it could take a few hours to get the location via Doppler. Just letting them know you're in trouble could be half the battle if you've left a plan with the people whose telephone numbers are in your PLB registration.
 
Police showed up at one person I knows house when his kid activated it accidentally.

YES They are Taken Seriously. If you use it when you dont really need it you may be fined or arrested. Its like dialing 911 on steroids
 
kenk said:
Here is one of the conclusions from the ETS Foundation PLB testing:

"Results from the gorge test suggest that Doppler location can be achieved even with a very limited sky view, though it may take multiple LEO satellite passes. While it may be possible to acquire a GPS location if there is a fortuitous confluence of sufficient GPS satellites visible during a period of time while the GPS receiver is operational, this cannot be counted upon in such circumstances."

So even with limited view to the sky rescue crews will hear the beacon and will likely get a location, though it could take a few hours to get the location via Doppler. Just letting them know you're in trouble could be half the battle if you've left a plan with the people whose telephone numbers are in your PLB registration.
Click to expand...

If we are talking about slot canyons I have serious doubt about how effective these would be. Forget the doppler. No one is going to be doing doppler search on your unit unless they know you are gone. The way the PLB notifies someone that you are in trouble is to notify a very few specialized sats. With your PLB seeing a very little piece of the sky and with very few sats that the PLB talks to, to announce your problem to the rescue coordination center (RCC) and only once or twice a day overhead if I remember correctly. Your chances that the sat you need to announce your problem to the RCC are probably pretty slim.

To give an accurate fix on your location the system must have at least 3 GPS sats to aquire a 2D reading and getting 3 sats to line up in slot is difficult enough. Also, if the sats are in the same plane, which is a very distinct possiblity in the bottom of a canyon the equation for location cannot be solved so again no location will be displayed.

I'm not saying don't get the PLB if you are going canyoneering. Just be aware of its limitations and always, always, leave an intinerary with someone you trust. When they eventually are looking for you doppler can be used but reflections and multi-path will drive them insane.

KR
 
EmsRescueGuy said:
Its like dialing 911 on steroids
Click to expand...


Excellent description. When a PLB goes off the entire nations search and rescue system goes into effect. No exaggeration. From the federal government on down.

And yes unregistered PLB's and false alarms really pixx people off. They get particularly pixxed off when it is both an unregistered PLB and a false alarm. Fines, etc. can follow.

KR
 
I don't have any idea how deep/wide slot canyons are, but here is the description of the gorge used to do a limited view of the sky test in the Equipped to Survive Foundation's "Second Evaluation of 406 MHz Location Protocol Distress Beacons".

"Inland Scenario Foxtrot was developed to assess the ability of the COSPAS-SARSAT system to receive an alert and derive a Doppler location in circumstances where the beacons had a very narrow and limited sky view, as when survivors are located in a narrow canyon. The location selected was within a narrow rock gorge through which flowed Aptos Creek. Estimated depth of the gorge where the beacons were placed was approximately 30-40 feet plus trees lining both sides. It was approximately 15-20 feet wide at the bottom and approximately 30-40 feet wide at the top at the point the PLBs were located. The beacons were placed on a rock shelf located to one side of the gorge.

The only access to the selected location was by traveling up the creek approximately 100 yards, which ran from wall to wall of the gorge in places. Ritter donned insulated waders and one of the Coast Guard Rescue Swimmers donned his dry suit and they waded up the creek, which was approximately 3 feet deep at its deepest, to place the beacons on the rock bar. The beacons were turned on sequentially with a 15-second interval and were left on for approximately 4 hours which allowed for 3 LEO satellite passes.

All three PLBs were picked up by the GOES 10 satellite, which would provide an "immediate" alert in an actual emergency. The ACR Prototype PLB was also picked up by GOES 12. It has been suggested by various experts that this may be the result of a lucky reflection off the rock wall of the gorge. ACR suggests, "the result is more a case of the beacon having a strong transmitter than it is a 'lucky shot'. Without ample power a reflected signal could never make it to the GOES 12 satellite."

All three PLBs were picked up by the Low Earth orbiting (LEO) satellites on their first pass, about 25 minutes into the test, which provided a Doppler location."

One of the PLBs did get a GPS fix in the gorge - likey from a reflected signal.

The full test results are at http://www.equipped.org/406_beacon_test2_toc.htm
 
kenk said:
I don't have any idea how deep/wide slot canyons are, but here is the description of the gorge used to do a limited view of the sky test in the Equipped to Survive Foundation's "Second Evaluation of 406 MHz Location Protocol Distress Beacons".

"Inland Scenario Foxtrot was developed to assess the ability of the COSPAS-SARSAT system to receive an alert and derive a Doppler location in circumstances where the beacons had a very narrow and limited sky view, as when survivors are located in a narrow canyon. The location selected was within a narrow rock gorge through which flowed Aptos Creek. Estimated depth of the gorge where the beacons were placed was approximately 30-40 feet plus trees lining both sides. It was approximately 15-20 feet wide at the bottom and approximately 30-40 feet wide at the top at the point the PLBs were located. The beacons were placed on a rock shelf located to one side of the gorge.

The only access to the selected location was by traveling up the creek approximately 100 yards, which ran from wall to wall of the gorge in places. Ritter donned insulated waders and one of the Coast Guard Rescue Swimmers donned his dry suit and they waded up the creek, which was approximately 3 feet deep at its deepest, to place the beacons on the rock bar. The beacons were turned on sequentially with a 15-second interval and were left on for approximately 4 hours which allowed for 3 LEO satellite passes.

All three PLBs were picked up by the GOES 10 satellite, which would provide an "immediate" alert in an actual emergency. The ACR Prototype PLB was also picked up by GOES 12. It has been suggested by various experts that this may be the result of a lucky reflection off the rock wall of the gorge. ACR suggests, "the result is more a case of the beacon having a strong transmitter than it is a 'lucky shot'. Without ample power a reflected signal could never make it to the GOES 12 satellite."

All three PLBs were picked up by the Low Earth orbiting (LEO) satellites on their first pass, about 25 minutes into the test, which provided a Doppler location."

One of the PLBs did get a GPS fix in the gorge - likey from a reflected signal.

The full test results are at http://www.equipped.org/406_beacon_test2_toc.htm
Click to expand...


This is actually better than I would have thought. I have looked over report but I want to read the report more fully when I have more time.

Like it says though. If the sats are catching a reflected signal, it must be a pretty strong transmitter.

KR
 
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