The problem with GPS is the illusion that it is generally regarded as being infallable by the user. Just as there are the ineviatable errors associated with maps (the map is only as good as the original accuracy of the survey together with the fact the map features can move e.g. rivers may change their course or dry up, cliff edges may receed over time, introduction of new roads and the plantation of new wooded areas with older wooded areas being cut or burnt etc) and compass errors (magnetic declination and local geomagnetism), the GPS also has associated errors with it. Some can be quite considerable if the GPS is not setup correctly.

Additional problems occour when aligning the computed GPS position in the WGS84 Lat/Lon coordinate system to the map wether it is a paper or electronic one. The electronic map may have even more errors associated with it because they may have been generated from the paper version. The paper to electronic conversion will again introduce some form of error i.e. the scanning and conversion from a bitmap image to a vector image. This may involve some considerable computer graphical editoring, which may again involve some form of human error.

General GPS errors can be helped along by ensuring the GPS almanac and Ephemeris details are upto date by leaving the GPS to download this information especially if the GPS has been turned of for a few weeks or months.

WAAS and EGNOS being turned on can help considerably with the GPS accuracy providing differential GPS to help eliminate mostly atmospheric and multipath broadcast signal errors. This will tend to improve GPS accuracy from around 10-20 metres (CEP) to 1-5 metres (CEP).

Ensure that the correct mapping datum and position format match the paper map which is in use. The conversion from GPS WGS84 to the local map such as UTM MGRS or OSGB grid involves some complex calculation as can seen from the following link
http://www.ordnancesurvey.co.uk/oswebsite/gps/docs/convertingcoordinatesEN.pdf

More modern higher sensitivity GPS models help with aquiring low power lock on to the satellite signals in wooded areas etc. Not all GPS's are created equal.

Ensure that the lasted firmwire for the GPS is also up to date. Some errors that might have introduced errors especially with coordinate transformations may well have been reported and consequently fixed.

If after ensuring that the GPS (with the latest firmware) has a good signal with a fresh almanac and Ephemeris and that WAAS or EGNOS is turned on and that the correct position format and datum are selected for the map you are using and you still find that the GPS is apparently giving the incorrect location then chances are the map itself will be wrong.

Generally I have not had a problem with my very basic Garmin eTrex when used in conjuction with the UK Ordnance Survey maps in providing a very accurate position. GPS accuracy in relation to the Ordnance Survey maps is a claimed 2 metres by Ordnance Survey.

I wouldn't trust the Garmin to point me in the right direction though. But that's what a compass is for.

What I do find interesting though is the idea that a GPS is somehow easier to use and therefore can be introduced to the navigator starting out before introducing map and compass work. Surely it must be the other way around.

I went head to head with Doug on this a while back.

I will say one thing in defense, perhaps, of my Brunton 8096 compass, it has GPS confidence circles. Meaning that when you transfer a point to a map from your GPS or just WAG (Wild Ass Guess)your destination, there is a stencil on the base plate for a 100 yard circle to put around it.

My greatest use for GPS is finding residences and common places of interest while driving. Have no idea where an address is in the greater metro area? Type it into my little nuvi and I now have a guided route to get there. For finding myself in the big woods, or on top of the mountain, maybe not so much. Up at elk camp I much prefer orienteering my way around, first by studying a map of the area real good before I ever get there, then by identifying landmarks I can hopefully use from any location nearby, then by planning my hiking so I have a good idea where I am headed and what will be around me.

This is the most intelligent response I've heard so far. A GPS is what it is, it's a tool with limitations. The main function of the GPS is to tell you where you are, not where to go.

This situation could have easily have happened with our without the GPS. If the families had gotten lost while using map and compass, almost everyone here would be admonishing them for NOT having the GPS, a la James Kim. With the GPS, they're being criticized for having too much dependence on it. It seems you can't win either way, there is always going to be the monday morning quarterbacks who will tell you it's wrong.

Who can say for sure that a map would have been any more accurate than their GPS was? I've been to plenty of places that looked fine on a map, only to find out the route is a dead end. At least the GPS maps should be updated more frequently than paper maps, but that still doesn't mean they're 100% accurate. Sure the GPS doesn't work in the forest, canyons, or snowstorm, but a map and compass don't work any better in those conditions either.

No matter what equipment you use, there's alwasy the possibility of getting lost.

I think I would disagree with you there. In a forest, you may not be able to do a resection, but you can calculate a bearing on your map and then walk your bearing. In a canyon, there are a lot of tricks canyoneers use. You can count the number of side canyons, checking them off on your map as you pass. You can shoot a bearing up each side canyon and check the bearing against the map. You can check off the twists and turns of the main canyon as you pass through them, marking them on your map. Again, you would verify that you're in the twist or turn that you think you are in by shooting bearings. Even in a snow storm, you can still calculate and walk a bearing.

Now, don't get me wrong, I'm not disagreeing with you overall. BobS's analogy with matches vs. a lighter is a good one. I'm merely pointing out that there are a few tricks left in the ol' map and compass bag even in the situations you point out above. Of limited utility under some conditions (whiteout), but tricks nonetheless.

You're correct, but I was thinking more along the lines locating your position vs navigating. If you have no idea where you are, taking a bearing would be of limited use. With a GPS you need a clear unobstructed view of the satellites to pinpoint your position, but a map and compass also needs clear view of your surroundings to do the same. Each one has their pluses and minuses. And you can get lost with either one.

If you've got the discipline to count landmarks or canyons, then you wouldn't even need a compass to tell you where you are. Of course, if you could do that, you wouldn't need a GPS signal either. hmm...

That's what woman are for, to tell us where to go!

Ahemm... by GOOD TROUBLE I meant that it was useful in my hobby as it just gave me just another good reason to get outside and have fun. Getting outdoors is "GOOD". The GPSr itself works wonderfully. Apparently the emphasis and <very big grin> wasn't interpreted correctly.

BTW, technically, I should have GPSr or GPS receiver instead of just using the acronym of GPS.

While out and about in the great wilds, I can usually get some pretty good accuracy even under heavy tree/brush cover. I have located caches to within 1 metre of the given co-ordinates on the GPSr in the bush although that was more luck and coincidence than accuracy. I have also used it in the mountains of Kananaskis valley south of Banff and had no problems with the high cliff ridges blocking too much signal. My 60CSx is one of the better models that doesn't suffer nearly as much as the Etrex line as it uses a helix antenna and a high sensitive receiver chip.

The newer Colorado/Oregon/Etrex H series GPSr are also very capable receivers under cover. My receiver will often pick up 8-10 channels in my home and almost always 10 or better channels outdoors. IN testing at my office tower in the middle of the bldg, I usually only get 2/3 channels because of the blockage with the structure.

Another factor is the ability to use the WAAS or ground based stations to increase the accuracy by a factor of 2-3x. In mountain cover you probably won't get WAAS reception but where I am on the prairies the nearest WAAS station is Winnipeg which was turned on last summer. The best accuracy I've noted on the receiver is 1.8 metres which is extremely good.

As far as maps go, I use both the 1:50k Canadian Topo and the North American City Navigator maps and switch to whichever makes the most sense to use. When I mentioned in my original article that I had problems with road locations - yes that has happened but it is always because of what tools the company used to generate the maps in the first place. Not every map will be bang on all the time, especially in areas of high urban development so they issue yearly updates.

When out camping, I probably don't use the GPSr as much as I will do when geocaching because I am not interested or require the higher accuracy but it is fun to create a track and then load it up in the computer or Google Earth and find out where I have been. The added sensors for altitude and compass readouts are bonus and satisfy my curiosity more than me using them correctly.

Anything else you curious about?