I'm new here, but came across this on the NPS Morning Report dated 1/3/07 (I added some paragraph breaks to make it easier to read):

http://home.nps.gov/applications/morningreport/

Big Bend National Park (TX)
Stranded Hiker Uses PLB To Summon Help

On the evening of December 30th, the U.S. Air Force notified the park that a personal locator beacon (PLB) signal had been received from a backcountry location within the park. Rangers headed to a backcountry campsite about six miles from the coordinates given by the PLB and found a vehicle registered to a visitor who had a solo hiker permit for that zone of the park. Two rangers then hiked to the approximate PLB coordinates, but were unable to find anyone in that area. They were joined by another team of searchers and a Texas Department of Public Safety (DPS) helicopter the following morning. The crew of the helicopter homed in on the 121.5 MHz distress transmission from the PLB within minutes of arriving on scene and soon spotted the hiker, who was waving a space blanket at them.

He had “cliffed out” on the side of Elephant Tusk peak, but gave the helicopter crew a thumbs-up signal indicating that he was okay. Although the helicopter was unable to land, the crew directed searchers to the man’s location, then ferried rope and climbing equipment to the rangers on scene. They climbed to his location and helped him down.

The man told rangers that he’d attempted to climb to the top of Elephant Tusk the day before. He’d cached his backpack, tent and sleeping bag and had made the ascent carrying only a space blanket, food, water, a whistle, an LED light, and a PLB. After topping a 40-foot chimney, he decided to turn back – only to find he couldn’t climb down from his location. He spent the night on a 6-foot by 50-foot ledge wrapped in the space blanket, with his PLB tied to a bush to keep it from being blown away by high winds. Overnight temperatures were just below freezing.

This incident marks the first time in Big Bend that a PLB has been used by a hiker to call in rescuers. Without the PLB and assistance from the DPS helicopter, it would have been extremely difficult to find and rescue the man in a timely fashion. The PLB probably saved his life. [Submitted by Mark Spier, Chief Ranger]

I know the area well. I'm surprised the Border Patrol's SAR team wasn't in on the rescue (probably were). I'm also surprised there was no mention of the climber leaving a hiking plan at the Ranger Station, especially in light of the fact that the guy was carrying a PLB.

Welcome to the forum <img src="/images/graemlins/wink.gif" alt="" />

Interesting. I didn't realize that the Border Patrol had SAR teams. Is this a full time SAR team or are normal agents only pulled together when needed? I suppose the answer to this could also depend on the location.

Yes, full-time in some locations (Arizona especially) and quick-response teams in others. All are trained the same though. They'd have been there in Big Bend and, as I mentioned, they probably were.

Nighthiker,
You might be right about that guy being a beginner, however:

I've been climbing and bouldering for more years than I care to admit, and it's happened to me many times. I don;t go climbing solo though. I've been in spots where, if it hadn't been for my climbing buddy(s) talking me through this route or that, I am sure I would have been stuck.

"A surprisingly common occurrence among beginning climbers, they become competent at climbing up but don't consider having to come back down the same way."

Yes, like nine-week-old kittens, creatures with a brain smaller than a walnut.

Oh, well, at least he did some things right.

Sue

Now I wish I hadn't admitted that I've "been there" too <img src="/images/graemlins/frown.gif" alt="" />

I'd prefer being compared to a nine-week old puppy though {pant pant} <img src="/images/graemlins/smirk.gif" alt="" />

I may be missing something but it appears that the park service had no way to locate or home in on the plb signal and had for the helocopter which had the direction finding equipment. I just left big bend the week before and it is remote. I would have thought or hoped that the park ranger had the ability to home in on plbs.

I wish the article would have said whether the PLB has an internal GPS or not, and how far the PLB coordinates were from the actual unit.

It is nice to know that the 121.5 MHz homing beacon worked as advertised.

Actually it would seem luck had nothing to do with it. Copying from our gracious host:

Chance favors only the prepared and equipped.™

I agree.

My guess is that it didn't though, or if it did, that it didn't work as advertised.

If a GPS had been involved and working right, the position should have been reported to within 10s of meters of his actual location - assuming that he was in a spot where the unit could have gotten a GPS fix.

On one of the PLB test reports I read it seemed like a number of the units failed to provide good GPS coordinates. This info about some GPS equipped units not sending good GPS position info was also reported on some Cospas/Sarsat site documentation I read.

Do PLBs give elevation as well as L/L?

The article above said 'He had “cliffed out” on the side of Elephant Tusk...', so I am assuming that he was quite a bit above the base level. If they don't, the rangers could have been within 50' of him horizontally, but he was too high to be seen. He may have only waved the blanket when he heard/saw the chopper, but if he didn't know the rangers were below him...

Sue

Interesting . . . Checking the Cospas/Sarsat spec, it turns out that the third of a mile figure isn't all that far off from their requirements for units with a built in GPS. While it looks like the location encoding scheme accomodates greater precision than that, it only requires the following:

"4.5.5.3 Internal Navigation Device Performance

An internal navigation device shall be capable of global operation and shall conform to an applicable international standard. An internal navigation device shall incorporate selfcheck features to ensure that erroneous position data is not encoded into the beacon message. The self-check features shall prevent position data from being encoded into the beacon message unless minimum performance criteria are met. These criteria could include the proper internal functioning of the device, the presence of a sufficient number of navigation signals, sufficient quality of the signals, and sufficiently low geometric dilution of precision.

The distance between the position provided by the navigation device, at the time of the position update, and the true beacon position shall not exceed 500 m for beacons transmitting the Standard or National location protocols, or 5.25 km for beacons transmitting the User-Location protocol. The encoded position data shall be provided in the WGS 84 or GTRF geodetic reference systems.

The internal navigation device shall provide valid data within 10 minutes after its
activation. Internal navigation device cold start shall be forced at every beacon activation. Cold start refers to the absence of time dependent or position dependent data in memory, which might affect the acquisition of the GNSS position. "

Did anyone happen to see what type of PLB unit the person used?

If PLB's give elevation it would be from a GPS at best, and from what I've read that is a pretty poor measure of elevation since it is relative to the datum (I think), which (I think) can be thought of as the mathematical model of the Earth's surface (I'm weak on the whole datum idea)

I don't think its phsically possible for the doppler method (using the 406 MHz signal) can determine elevation. It just identifies the point in space - or actually a line - that is at a right angle from the source.

If there was a GPS involved my guess is that since it was on the side of a cliff the GPS didn't see enough satellites to get a good position.

Ken

While driving and passing those elevation signs in the mountains, my Garmin is easily within ~50 ft. It would probably be more accurate if I slowed down. Hiking it seems to be quite accurate relative to topo maps. But that's a 12 channel GPS receiver. How many channels does it take for a GPS to meet SARSAT/COSPAS spec? It probably has that much accuracy in elevation too. ?500 yards?

Yeah, I know what you mean.

The best explanation I've read of the PLB system is Doug's description in the PLB Test report on ETS.org. The link is http://www.equipped.org/406_beacon_test_background.htm#How - scroll down about 1/3 of the way to the How COSPAS-SARSAT System Works.

Without a GPS the PLB system uses the Doppler effect to get a position.

Picture yourself hanging out your car window while driving at a moderate speed past someone blowing a loud whistle. As you approach the whistle will sound higher pitched than it will once you've passed it. Its pretty likely that you could signal at the point when the pitch changes and fairly accurately identify the whisle's location, at least relative to the entire car ride. The LEO (Low Earth Orbit) satellites do the same thing.

If the 406 MHz beacon doesn't contain GPS location information, It can take the LEO satellites up to 90 minutes for a satellite to pass by the source of the signal, which is when the Doppler effect can be heard and a location determined. The maximum time to Doppler location decreases as you move away from the equator, so in the 48 states it will take less than an hour to get a Dopplier location. The Dopplier accuracy is about 1.5 miles.

On the other hand, GEO satellites can almost instantly receive the 406 MHz beacon with GPS location information since they are in geostationary orbits around the equator and are in constant view of large portions of the Earth (excluding the artic/antarctic areas - the LEO satellites can still see those and hear the Beacon with GPS location). The accuracy of GPS location isn't a good as a handheld GPS because some of the data is truncated (as I understand it), but it still is within about 350-600 feet.

The PLB with a preloaded GPS coordinate will provide the closest thing to a 10 second signal, but the ACR PLB will only hold that location in memory for 4 hours.

Looking at Doug's PLB test results, it looks like a PLB with a good view of the sky will take 1.5-2 minutes to be able to send the GPS location.

One thing that is interesting is that in order to save power (GPS's take relatively lots of power), once a good GPS location is obtained the ACR PLB shuts down the GPS and then it turns the GPS back on to look for a new location every 20 minutes. That seems like a reasonable comprimize to keep the 240 MHz beacon functioning as long as possible (24 hours minimum for the ACR PLB).

I'm such a geak!!

A gps that isn't used much will take a long time to get a position fix. If you use it in montana and then in texas months later it will take several minutes to get a fix. The last time I used my garmin geko 301, I thought it was broke because it was around 10 minutes to fix. After that, the other gps fixes took less than a minute on that same trip.

If I'm reading the text below correctly, per the Cospas/Sarsat spec, the beacon position can't be updated more frequently than once every 20 minutes.

The beacon shall commence transmissions upon activation even if no valid position data are available. Until valid data is available, the content of the encoded position data field of the message shall be the default values specified in Annex A. The first input of position data into the beacon message shall occur as soon as valid data is available. If the beacon has the capability to provide updated position data, subsequent transmissions of the updated position shall not occur more frequently than every 20 minutes.

If, after providing valid data, the navigation input fails or is not available, the beacon message shall retain the last valid position for 4 hours (± 5 min) after the last valid position data input. After 4 hours the encoded position shall be set to the default values specified in Annex A.

The requirement for cell phones to provide location information and volumes of units involved has had an effect on the development of newer GPS chip sets that acquire the satellites much faster - and use less power to do so. An example would be the newer GPSMAP x versions from Garmin that get fixes faster and in poorer signal environments than their previous version.

This should help newer PLBs equipped with those chipsets report initial positions quicker.

I think it has more to do with a change in location than time-since-last-use. If the GPS is far away from its last known position I think it may take a bit more time to "map" the new satellite positions. On some mapping GPS's you have an option of telling it your current location to speed things up.

Again, I understand your concern about only getting postion updates every 20 minutes, but the way I look at it is this:

On land, once you've activated a PLB you shouldn't be moving anyway. If for some reason you HAVE to move, then after 21-30 minutes searchers will have two locations on record and will have an indication of your direction of travel. I'm not sure if the locations have a time-stamp on them. If so, they'll have a sense of speed too.

If in big water, you will almost certainly be moving due to wind and currents. Even then the same thing holds. In 30 minutes they'll know the direction of travel and may have an approximate speed.

It seems that SAR crews will take some time be put into action and to get to your location, and getting a fresh location 20 minutes after the initial location seems about right. They should be able to get regular updates on location changes via radio - I would guess. Plus if so equipped and trained they can also use the 121.5 MHz homing beacon from the PLB to find my exact positon.

I don't expect my PLB to get me rescued in 10 minutes. I figure an hour or more is highly likely, which is why I still need to be "equipped".

Ken

Is anyone else wondering how having the PLB might have contributed to him getting stuck in the first place? Just to play devil's advocate, it seems like we have a guy that went out alone, might not have left a plan with anyone else (other than getting a permit), attempted something beyond his ability, left a majority of his equipment behind, and relied on his PLB as a lifeline to get him out of trouble. To put it another way, does having a PLB make him prepared, or just more likely to make risky decisions? Because if he didn't have one, I would think we'd have a very different opinion about him right now

Without the PLB he'd likely have been dead.

Since I don't climb or know all the inputs to his decision-making process, I can't judge him on decisions made.

I know in my life I've made some real foolish decisions and luckily had the skills or equipment along to bale me out - for the most part. I've fallen through thin ice and had people and gear to help get me warm again. I've driven into bad winter storms thinking my 4WD truck would take care of me - and it did. I've gone camping in nasty weather with forcasted high winds and thunderstorms thinking my gear would take care of me - and it did. I can think of one time as a kid where I thought my car could handle the road, but it didn't and I ended getting pretty messed up (broken back - ripped up face). We all make decisions and some of them don't work out for the best, that is where good plans, good friends, good gear, first aid kits, survival kits, cell phones, and PLB's come into play.

The point is to be equipped to survive those bad decisions.

I thought lost soloists just chew their arm off?



I think it will be a sad day when someone that goes out alone in the woods is condemned. Some of my best days in the field were solo.

This guy went prepared and his preps paid off.

He's been found by the Chile navy...

I get the impression that some people think that the PLB is the magic survival talisman. If you have a PLB, you don't need matches, a compass, map, sleeping bag, signal mirror, water, etc. Just stash your stuff & climb. The PLB will save your life, but only if you don't freeze to death or die of dehydration first. Rescues have been delayed by bad weather, exactly the situation when you will need the usual survival stuff the most.

Good thing he got found. I guess he called his sister in the U.S. on a satellite phone and told her he was in trouble and to get him help. They knew roughly where he was, but a beacon would have done much better - at least it would seem.

It sounds like he is really one tough dude, but that he was really scared for his life for a time.

I agree. I'm not condeming him for going solo, in fact I think sometimes going solo is the best way to go. What I was saying is that he took unecessary risk while alone, which I suspect were because he was relying on a single electronic device to get him out of trouble.

The problem I see here was this was no accident. Unlike the Kims, who took a wrong turn or got lost, or the Mt Hood climbers who got caught in a snowstorm, or even the runner who fell and hurt herself, there doesn't seem to be any extenuating circumtances to have caused his problem. From what I read in this case, he didnt' fall and get injured, no sudden unexpected weather change, no falling rocks to prevent his going back the way he came. Nothing at all that was unforseen. He basically just kept going forward until he wasn't able to return. Where was his climbing gear? Why would he leave almost everything behind in an area where it gets below freezing? If this was like the Aaron Ralston case and he had injured himself because of a falling rock, then used the PLB to call for rescue, that's great, it's what they were designed for. But I don't think they were meant for people to take them along just so they can go as far as they want to and have someone else pick them up when they can't make it back.

I think one of the first things people learn when traveling outdoors, especially when traveling solo, is that you don't go headfirst into the unknown without knowing how to return. Just like in hiking, if you dont' know what's ahead, dont' keep going until your water runs out, turn around when you still have enough water to make it back. Or in canyoneering, don't pull the ropes down unless you know for sure there's another exit out of the canyon. I would think climbing would be the same way, don't climb up what you can't climb down, unless you know there's another way down.

My thoughts exactly. ChaChing

It's both location and time-since-last-use. They download the parameters for a mathematical model called an almanac which they use for a first-guess location of the satellites. The satellites drift away from where the almanac says they are, so it becomes less useful over time and effectively expires after about 3 months. Downloading a new one can take half an hour or so; it's transmitted by all the GPS satellites, but slowly. So if a GPS unit hasn't been used for over 3 months, it can take a while to get fixes until it's held a fix for half an hour or so.

There is also another model called the ephemeris, which is much more precise and expires after a few hours. That's the one it actually uses to fix your location. It expires after a few hours, which is why a "warm boot" is faster than a cold one.

Actually, his boat was equipped with an EPIRB. Apparently, his sister told him to turn it on when he got a call through.