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#82377 - 01/08/07 05:38 PM Stranded Hiker's Personal Account of PLB Rescue
KenK Offline
"Be Prepared"
Pooh-Bah

Registered: 06/26/04
Posts: 2208
Loc: NE Wisconsin
Doug's BLOG points out the personal account of the guy who was stranded on a clip and used his PLB to get rescued.

http://www.bigbendchat.com/viewtopic.php?t=2695&start=0

He had an ACR PLB w/ GPS and rescue did call his home (wife) and he says they were searching 1/4-1 mile away from hi sactual location from 7pm to 4am. Finally they brought in a helicopter and he got its attention by waving his emergency blanket.

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#82378 - 01/08/07 07:54 PM Re: Stranded Hiker's Personal Account of PLB Rescue
Husky71 Offline
Stranger

Registered: 12/17/06
Posts: 15
Loc: Southern California
Interesting.

He states : "And throughout all of this, I had no idea that anyone was down there looking for me. ACR "promises" that if you spring the extra $100.00 for the onboard gps, then the PLB will locate you within a 10 foot area, enabling that SAR to find you within 4 hours, worst case scenario. 4 hours came and went."

However on ACR's web site, the specs listed for their TerraFix PLB state the following: "Onboard GPS (P/N 2798.4 only) acquires LAT/LON when the unit is activated, your LAT/LON is transmitted as soon as acquired providing rescue agencies with your exact position to within 100 meters (110 yards)."

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#82379 - 01/08/07 08:06 PM Re: Stranded Hiker's Personal Account of PLB Rescu
Russ Offline
Geezer

Registered: 06/02/06
Posts: 5357
Loc: SOCAL
As he notes further down the linked page. Still, SAR was much further than 110 yds out.
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#82380 - 01/08/07 08:18 PM Re: Stranded Hiker's Personal Account of PLB Rescu
Arney Offline
Pooh-Bah

Registered: 09/15/05
Posts: 2485
Loc: California
Sounds like a salespersons's smooth talking about GPS' capabilities in general versus the "fine print" on the actual product itself. For civillian use, isn't GPS accuracy in the 3m/10 ft range? Which would jive with the guy's assertion of what he was told.

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#82381 - 01/08/07 08:58 PM Re: Stranded Hiker's Personal Account of PLB Rescu
Husky71 Offline
Stranger

Registered: 12/17/06
Posts: 15
Loc: Southern California
Quote:
Sounds like a salespersons's smooth talking about GPS' capabilities in general versus the "fine print" on the actual product itself. For civillian use, isn't GPS accuracy in the 3m/10 ft range? Which would jive with the guy's assertion of what he was told.


The ~10 m range is what I originally thought too until I looked at the Cospas-Sarsat spec's for the transmission from the beacon. I haven't taken the time to completly read that part of the specs, but If I understand correctly, the location information transmitted back by the beacon is limited to 4 s of lat/long in the best case - it could be worse like 2, 4, or 15 minutes of lat/long.

4 seconds of longitude works out to about 123 m for equatorial latitudes and around 95 m for mid-North American latitudes. 4 s of latitude is about 123 m regardless. So figure a something a little larger than a 100 m x 123 m area as a best case fix.

If it's 4 minutes then the area grows to 5700 m x 7400 m for NA latitudes.

That's where the 121.5 MHz beacon starts to come in handy for RDF location of the beacon by local SAR folks.

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#82382 - 01/08/07 10:14 PM Re: Stranded Hiker's Personal Account of PLB Rescu
JohnN Offline
Old Hand

Registered: 10/10/01
Posts: 966
Loc: Seattle, WA

Quote:
Sounds like a salespersons's smooth talking about GPS' capabilities in general versus the "fine print" on the actual product itself.


It's probably also partially design-meets-the-real-world.

Personally, even if they said 10' or 100' or 300', or some time period I would normally assume that there was a good chance that real world performance would not match, both for technical and human reasons.

The good part is that it did work.

FWIW, it's nice to see a lessens learned from an actual SURVIVOR. It's also nice to see he survived because he planned ahead.

I suspect there will be some discussion here if he was prepared enough, and questioning the mistakes he made, but the in the end, even though he was only going to be gone for 30 mins, he took a PLB and a space blanket, both of which contributed to saving his life.

It's also nice to see him own up to his mistakes. It takes some guts to say to the world that you goofed up.

He also credits ETS for learning about PLBs. Nice to see Doug's PLB work and crusade pay off.

-john

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#82383 - 01/08/07 10:18 PM Re: Stranded Hiker's Personal Account of PLB Rescu
oldsoldier Offline
Old Hand

Registered: 11/25/06
Posts: 742
Loc: MA
Even with a 1km X 1km search area, thats a HUGE difference from "he was last seen walking on this trail, in this direction".
Anything to cut down on search time is great. Getting people to the exact area to search reduces risks to both the lost & the searchers.
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#82384 - 01/08/07 11:05 PM Re: Stranded Hiker's Personal Account of PLB Rescu
KenK Offline
"Be Prepared"
Pooh-Bah

Registered: 06/26/04
Posts: 2208
Loc: NE Wisconsin
The original post about this story here on ETS Forum that was posted some time back indicated that he was found by the helicopter usign the 121.5 MHz homing beacon. It doesn't sound like that is truely the case here. It sounds like it was more likely that they found him through his signaling.

If the SAR team had tuned into the 121.5MHz homing beacon they should have at least had a direction to head toward and maybe even triangulated his (the beacon's) position in fairly short time. In one of Doug's discussions he'd pointed out that many SAR teams either don't have the 121.5 MHz equipment or are not trained to properly home in on it.

There is also the posibility that along side the cliff the GPS was not able to lock onto sufficient satellites to get a GPS location. The location provided by the beacon might have been a Doppler location, which has an error of 12.5 miles or so. The victim would have known this by looking at the lights on his PLB - if the GPS LED was blinking green then he had sufficient signal for a GPS location - if after 20 minutes it was still blinking red, then he would have been relying on a Dopplier location.

The other lesson learned is that he should certainly have a had a signal mirror (though we're not sure of the sunlight available) and it would have been good to also have a nighttime signal devise, such as the Rescue Laser Flare.

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#82385 - 01/08/07 11:52 PM Re: Stranded Hiker's Personal Account of PLB Rescu
ducktapeguy Offline
Enthusiast

Registered: 03/28/06
Posts: 358
Quote:
FWIW, it's nice to see a lessens learned from an actual SURVIVOR. It's also nice to see he survived because he planned ahead.

I suspect there will be some discussion here if he was prepared enough, and questioning the mistakes he made, but the in the end, even though he was only going to be gone for 30 mins, he took a PLB and a space blanket, both of which contributed to saving his life.

It's also nice to see him own up to his mistakes. It takes some guts to say to the world that you goofed up.


I agree 100%. We went over this in the last thread, but it is nice to get the story first hand from the survivor. It's really easy for us to be armchair quarterbacks and criticize (which is why I do it so often, because it's just so easy <img src="/images/graemlins/grin.gif" alt="" />) but I do have a lot more respect for him after hearing the story from his point of view. He admitted the the mistakes he made, didn't try and point the blame somewhere else, and he learned from them. I'm glad the ending turned out the way it did.

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