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Comment by chrissnell | Hacker News Reader

EPIRBs are incredibly handy devices in an emergency. Unlike SPOT trackers and such, the response is managed and coordinated by the US military. If your EPIRB signal makes it out, someone will come looking for you.

They work on dry land, too. Very useful to have if you like to do trips to the desert backcountry. I ended up purchasing a satellite phone after ditching my SPOT tracker but if I had to do it over, I'd just buy the EPIRB.

The marine versions activate automatically when dropped in the water. Typically, on a sailboat, you would lash it somewhere on deck where it would pop up to the surface and activate if the boat sinks. The outside of a life raft shell is one such spot.

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> the response is managed and coordinated by the US military.

Who is responsible will vary around the world. If you're at sea it will likely be some sort of coast guard or possibly even a navy, but on land it's often a civilian agency charged with rescuing people who've got into trouble far from civilisation or even handed off to volunteers.

COSPAS/SARSAT (the satellite technology that makes these beacons work) is a rare example of Cold War co-operation on technology for peaceful ends. Hence why SARSAT makes obvious sense in English (Seach And Rescue SATellite) while COSPAS is Russian.

Before all this starts, there are analogue radio beacons. Those are pretty dumb, you can still find them in some personal planes flown by pilots too cheap to upgrade - they just play a siren tone on a fixed reserved frequency when triggered. If somebody is tuned to the reserved frequency and close enough, they can hear your beacon, with some pretty easy technology a group can triangulate and find the emergency. Might save your life, if people are searching and if you can survive maybe a day or two while they look.

COSPAS/SARSAT says wait, we have satellites, put a radio "mirror" on a satellite at that frequency, and now we don't have to search any more. We sit at the ground station for the satellite, we hear distress beacon sirens from existing beacons on the ground, we can use mathematics to work out based on where the satellite is and the Doppler effect where the radio beacon is in a few minutes.

That works up to a point, but there sure is a lot of other junk that's broadcasting (intentionally or not) on the reserved frequency, and you've got no idea when your rescue helicopter scrambles are you going to find: A small plane with no filed fight plan and six badly injured people? One lone hiker who is just lost in the hills? A pile of garbage somebody threw out which happens to include a radio beacon with just barely working batteries? Could be anything. Almost always it was nothing. That's expensive and bad for morale.

So, modern COSPAS/SARSAT beacons are digital, and the satellites are now smarter. The beacon has a unique identifier and if fitted with or connected to a suitable receiver (very common on boats and somewhat common elsewhere) it can transmit its GPS co-ordinates.

This means now the base station isn't trying to guess if this is a beacon with a low battery or a garage door opener, they know instantly it's beacon #4843931 and it says it's fourteen miles off the north coast of Scotland. This cut false alarms by an order of magnitude at least, and reduced search time to almost zero. False alarms are still the majority of all alerts though - emergencies don't happen that often and humans are lazy and incompetent leading to false alarms.

The current work on COSPAS/SARSAT is return link. Right now you trigger the beacon and then... maybe you get rescued. But that's not great emotionally and we know in some emergencies hope is key to survival. Is anybody coming? If you're clinging to the wreck of a yacht ten minutes can seem like an hour, surely the beacon you triggered just isn't working? So return link is a mechanism by which GPS messages are used to tell your beacon "Received. Rescue coming" and perhaps some day more complicated messaging like "Cannot Land. Ground team on its way to you. Stay here".

I have volunteered for a marine SAR service in the U.K. and I’ve been on shouts looking for these things. We once looked for the old fashioned kind where you only get the location to within 50-100nm at first, with it getting a bit more accurate every 30(?)mins as the satellite passes over again. Searched all night only to find it fell of a shelf in someone’s shed.

In case anyone is interested here’s a simplified version of what happens if a beacon goes off in a U.K. sea area. The coastguard marine rescue coordination centre receives the alert, depending on the type of EPIRB initially the information could be as little as the location to within 100nm. If they get an ID number they look up the details to see which vessel/aircraft it’s registered to and they call the person listed on the register to find out if it’s an accidental activation. Meanwhile they are starting the process of tasking search and rescue units. Unless it can be confirmed it’s an accidental activation they will request at least one RNLI lifeboat and typically task a coastguard helicopter as well. They can also broadcast a Mayday on channel 16 to oblige all vessels nearby to take part in the search. The lifeboat service is a charity which is independent from the government so the coastguard has to contact the launch authority for the closest lifeboat station, the LA agree to be tasked and at that point crew pagers go off. The crew tumble out of bed (or work) and run or drive to the station. From at work or asleep at home to fully kitted up doing 25kts at sea is about 10mins. The coastguard can set our pagers off directly to save a few minutes if it’s super urgent, but the decision to put to sea is still made by the RNLI. Our patch extends out into the Atlantic as far as our range will take us, about 125nm at full speed, and about 30 mins north or south to the next boat’s patch. A fairly typical shout will see us on scene in under 45mins from launch. In our location the helicopter usually makes it there at about the same time as us give or take 10mins. The longest shout I’ve been on is 18 hours. A more typical one would be 3-4hours and our boat has two 1600hp diesels so we might use 1000 litres of diesel (costing about £500), about 1/6th of the tank mostly in getting there and back. The boat has a crew of 7. Apart from the Coxswain (the RNLI word for skipper) and the Mechanic the crew are all unpaid volunteers, we get a token amount of money per hour at sea, maybe £1, not sure. There is a pool of about 25 crew and we train for about 4 hours per week. As to what we can do when we get there. Our training covers seamanship, things like rope work, navigation, watch keeping, emergency drills. But also specific SAR techniques and equipment. So we have things like a portable salvage pump that can shift about 1m³ in 1-2minutes, line throwing rockets, crane launched daughter craft for shore search, breeches buoy etc. Most of the crew have also done basic medical training, things like CPR, giving oxygen or entonox, inserting airways, bag valve mask, tourniquets, combat bandages, etc. We work in close coordination with the coastguard helicopter and with land based paramedics. Our boat is pretty specialised, RNLI all weather lifeboats are designed to survive a capsize and self right again afterwards and we have customised diesel engines that can operate upside down at idle power for short periods of time. As such we can go to sea in pretty much any conditions.

I've lived a good part of my life in IJmuiden/Heemskerk in NL, near Wijk aan Zee where one of the SAR stations for the region is located. The North Sea can be pretty nasty in that area (well, the sea can be nasty anywhere but the particular underwater geometry makes that area quite dangerous even in good weather).

My office overlooked the main waterway and what always struck me is that if there was bad weather incoming you could see all the pleasure craft and the merchants that could make it in time make a beeline for the harbor and the locks while - not all that rare - the pilots and the SAR vessel were going the other way, straight into the worst of it.

Most impressive.

One upside to tools like the Garmin (and I _think_ the newest SPOT) is you get 2-way communication. This is good to describe your specific need (helicopter evac vs 2 people on foot to carry a stretcher) and location (are you stuck on the side of a cliff for example).

I had a motorcycle accident in Tajikistan and it was invaluable. I wrote to a friend who could check the available options for me. I'm really glad I had it with me. Unfortunately I forgot it in a taxi a bit further down the road.

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