In my mind, the PLB. You can learn map & compass navigation skills if you don't have experience. Its plenty possible to navigate without a GPS. The most important thing is to know where you are and don't try and navigate in an area above your skill range.

However if you become injured and unable to move, knowing where you are doesn't help much (GPS won't do you any good with a broken leg). Having something that can tell others where you are would be much better. Plus on the off chance you get lost, and your life is in peril, it can help there too.

Not to mention if all your navigation requires a GPS, what happens if it runs out of batteries, or otherwise breaks.

What does "tired and dehydrated" mean exactly? Dehydrated could be anywhere from slight discomfort to close to death.

As a general observation, lots and lots of people fail to drink ENOUGH when outdoors, even if water is abundant. Cleaning water takes time and resources, no matter what method you're using.

It's not only about having the right gear - you have to know how to use it. In this case the gear can be as simple as a pot, and the knowledge part is simply being aware that you should use that pot a lot more than your reflexes and feeling of thirst and general discomfort tells you.

The GPS is an EXCELLENT tool for showing not only where you are, but where you should go - and where you have been. The last part is also important because your track should tell you that you're heading in the wrong direction.

Being able to check that the datum of your map and GPS match is a very basic, essential GPS skill that you should know before heading into the brush. Same with declination.

That being said, I have to disagree that user errors on declination or datum would have been a likely cause of more confusion. The difference between the relevant datums in that area (nad27? nad24? versus the wgs-84) would have been how much exactly? My guesstimate is less than 1 km, perhaps someone with knowledge about the most likely maps over that area (BruceZed?) would like to chime in. Say the difference is half a kilometer. This is plenty for the GPS coordinates to put you, say on the east river bank when you're absolutely to the west of it. Which will cause confusion and perhaps make you distrust the GPS. However, the map display on your GPS (if you have one - most units sold today do!) will show your positon without any datum shifts, and with your TRUE heading (prior to any declination errors).

IMO, the GPS should not be discarded as a VERY valuable navigation tool based on a few stories about user errors. Some people will make mistakes and be led astray in a peculiar set of circumstances. Many, many thousands more have been saved from NOT having a 3 day survival episode. You never hear anything about them.


The biggest problem with a GPS is a combination of these factors
- it is so easy and intuitive to use that it undermines the motivation to learn and train basic navigation skills (map and compass)
- the batteries will die (bring spares!)
- a solid knock or a tiny drop of whater in the wrong place is all it takes to kill even the most robust GPS

Navigation with a good old fashioned paper maps and compass is an essential wilderness survival skill, no matter how fancy your GPS is. Unless, of course, you actually enjoy being lost and totally helpless when the unit dies.

There rescuers said they were dehydrated so some part of their water purification system was not working. [/quote]

Somewhere it should be pointed out that when thirsty and dehydrated, it is important to drink water and stay hydrated, even if the water is polluted.

Two things: There is a good chance the water is fine to drink without treatment, especially in pristine or fairly pristine mountain environments when there are no obvious contaminating sources in the watershed (the higher you are the better).

Second - even if the water is polluted, it is far better to stave off the immediate effects of dehyrdation, which can all too soon render you DRT. If you incur a case of diabolical flunkabetis, you will at least be back in town where the situation can be treated.

Wandering around the mountains of Arizona in the 50s, I and my companions drank freely from untreated water sources on many occasions. Cases of water borne illness - exactly none. That was a time when very few were backpacking or climbing, so we may have been fortunate.

I would be more cautious today, but if there were no other way, I would drink up, stay hydrated, and deal with the consequences later.

Lastly, "dehydrated" is a very imprecise term, as has been pointed out. Most of us probably hike most of the time in what is actually a mildly dehydrated state.

Here is a short Youtube video (not my video) of the rough, general area the hikers were probably in. The closest I have been to that area is on the other side of the mountain on the right in the video at about 34 seconds

GPS will tell you with very good accuracy where you are on the WGS-84 Geode, but lets assume some worse case errors which can occur for a common GPS unit with an inbuilt electronic compass and a paper map (NAD27)

Lets assume that the NAD27 datum hasn't been selected on the GPS reciever and instead is set to the default WGS-84 datum is at its maximum - this will be around 200m.

Lets assume that that WAAS is turned off (default) and the GPS etc has a somewhat limited sky view poor HDOP etc and the GPS error is 40m

Lets assume that the Magnetic declination is quite high at 16 degrees and the Magnetic declination has not been accounted for in the GPS, and it remains zero, i.e. the GPS has been set to True North.

Lets assume that you want to get to a way point on the NAD 27 map and you are using the electronic GPS compass, which has a +-2 degree error and the waypoint you need to navigate to is on a grid bearing of 0 degrees 1000m i.e. 1Km directly north on the NAD27 grid.

If all these errors combine in the worst case we have 200 + 40 + (sin (2 + 16) x 1000) = approx 550 metres away from the waypoint. The situation can get even worse if the Mag declination is entered incorrectly on the GPS i.e. 16 degrees East is entered on the GPS as 16 degrees West.

Now if you happen to now come across a another trail (which may well be the incorrect one) and you let it do the navigating for you then you could quite easily end up being turned around.

But GPS should allow you though to fix this problem quite readily by telling you where you are again once more with another fix, the difficulty once again is if the GPS has not been setup properly (as the GPS user doesn't know how to), is getting the GPS to tell you which direction to go to get back on track.

But once the same mistake is made again and you head off in the wrong direction once more then the navigational panic will probably start.

Even with GPS systems with electronic maps (most GPS electronic maps are inadequate i.e lacking contour height detail information compared to the paper formats), skill is also required to think in 3 dimensions when working with nothing really anything more than contour map lines you find at the higher altitudes.

I hesitate to get too picky, particularly if I wasn't there -- and who knows about the accuracy of press accounts.

Still, to be so completely turned around does seem like a lack of basic outdoor skills. You can't take along a compass as an amulet or lucky charm; you have to know how to use it. In this case, even a consideration of "which general direction should the sun lie in if we want to go east?" might have been really helpful. You have to keep an eye on the big picture in navigation.

HJ

Am_Fear_Liath_Mor,

Thanks for illustrating the various sources of errors in GPS navigation.

I have one little caveat: The GPS simply isn't used the way you describe. The electronic compass is just a useless battery hog. The best, easiest and most intuitive way to use a GPS is to use waypoints and see how your position is displaced on the GPS screen in relaton to those waypoints.

Tell your GPS "I want to go to that waypoint (or place your marker on the map)" and you have lots of fancy graphics showing you if you are dead on or need to veer left or right. No need to ever use the compass, neither electronic nor conventional (but you need the conventional as a backup).

So the most relevant inaccuracy is the difference between the different datums (nad27 versus wgs-84). In your example you've used 200 meters. In my neck of the woods, the difference can be as much as 400 meters between ED50 (European datum, 1950, still used on many nautical maps and some really old topo maps) and WGS-84. And - that difference is only relevant when you do translate coordinates from your paper map to your GPS, or vice versa. The GPS map display will show your correct position, no matter what datum the GPS is set to. (And yes, even the best GPS map display is totally inferior to a good topo map, which gives you both the fine details and a large overview without a need to zoom in or out).


200 or 400 meters may be close to insignificant or really make you doubt both the GPS and your mapping skills - it depends of what kind of features that is between your real and your fake position. It could send you down the wrong trail, into the wrong water shed (valley) or put you on the wrong side of a river or a road. But a glimpse on the gps map display would set you right.

There is also an inaccuracy when dealing with the coordinate grid of a topo map. On a 1:50.000 map with a one kilometer UTM grid you are really good if you can do that with 100 meter accuracy (plus/minus 50 meters, or one millimeter on that scale). A user inaccuracy of 400 meters when tired, under stress and so on is entirely plausible.

If the party is too clueless to set up the GPS right, then they're quite likely to be clueless regarding terrain association and general landnav awareness. I have had people as diverse and supposedly knowledgable as pilots and SAR techs not be able to explain to me what the difference is between NAD27 and WGS84 datums. I've asked said personnel "what datum do you use with your GPS system?" and the answer was "decimal degrees". Further prodding did not yield anything close to the correct answer.

You can dream up all kinds of accumulated errors to be made with the GPS. But if that's the case, the people are also not going to be able to get all Lewis & Clark with they're big bad selves and be geniuses with map, compass, and terrain association.

The GPS is a fantastic tool in the hands of a capable user. Don't blame the horse for the rider's failure.

Even without having a full picture of the facts, it's still clear that they made some very basic errors and didn't seem to be very outdoor savvy. They were fortunate to run across a cabin. Reading the article it sounds like they had access to water but couldn't treat it. I agree 100% with the previous posters- drink the water and deal with the consequences later. In that area the water was probably fine, and of course it's easier to treat illnesses caused by water borne pathogens than it is to treat death from dehydration.

There's a risk of being a "Monday morning quarterback" but cases like this do offer instruction to us. We should examine cases like these to glean insights that can teach us something. It's easy to get turned around. The worst thing they did once they realized they were lost is to keep moving. It's human nature but the worst thing you can do. I'm not sure why they didn't build a signal fire once they reached the cabin; did they not have any means to build one or did it not occur to the them?