View Full Version : Thoughts on GPS use?

01-16-2012, 10:31
Im looking at combo the etrex 20 and the Trail-head Series maps for the AT....

I dont intend to use it as constant running only for when ever i want to turn it on and look ahead and such....

one less thing i got to water Proof i guess... and ive been wanting a reason to buy a GPS so imagine this is a good excuse....

i know i dont have to have maps... but id like some thing at least

Do yall think it is a system that could work?,...

01-16-2012, 10:47
There are two usenet groups, at least one of them very active and occupied by intense users, and at least a couple of good websites/forums that talk endlessly about GPS's.

I am not current except as I need to touch base to be satisfied that my old Garmin 60csx is, on balance, still the best for backpacking.

I used an Etrex, two different models, years ago and they were horrible under tree cover. Nothing was bad enough, but they often displaced me randomly dozens of miles. Sensitive to how you held them, how they were pointed, metal in your pack, signs of the Zodiak for all I could tell. Just unacceptable. Maybe they are better today, I don't care, the 60csx is better.

01-16-2012, 11:56
I would never use one in a million years, but if you're into that, then go for it. It sounds do-able.

01-16-2012, 11:56
I just bought an eTrex 20 after much research and am happy with the device. Much improved over my old eTrex Legend model. Reception is way better too.

I got an Amazon class 10 micro sd card and imported the AT gps waypoint data from the ATC website for future hikes.

On my 2009 thru hike I just used a guidebook and got by just fine. If I do over I'll carry a map for Maine and New Hampshire only. You'll find navigating the Whites a pain in the arse due to so many connecting trails. That's why thru hikers have knife marked all the trail signs there with helpful arrow markers. Even then it's confusing.

01-25-2012, 00:56
Completely unnecessary for an AT hike unless you simply want a gadget to play with. It's so well blazed it's tough to get lost.

01-25-2012, 04:36
For a thru-hike no I would rather have a guide book, its just much more detailed. For any other hike, sure its just good fun.

01-25-2012, 07:25
It is a possibility for sure and would work fine if you wanted to carry it. Personally i would bring an iphone or other smartphone , they have gps and you can download the maps(satellite,topo,road,and hybrid available from most gps programs) to the phone for offline use, not to mention its also a phone, camera, video camera, and email/internet access if wanted/needed. I only carry my 'real' gps on multiday off trail trips now. I also carry a 9900mah battery pack that can recharge my iphone about 5 times.

01-25-2012, 21:21
GPS on the AT is just extra weight to lug. But, if traveling wilderness cross-country or a trail like the CDT, it can be a handy item to have. Won't need one on the PCT either.

01-25-2012, 21:29
Yep, agree with previous comments. Don't need a GPS for a thru hike on the AT. Just a guidebook will serve you well.

I use my eTrex 20 for short hikes, weekenders, and for good ol' fun.

01-26-2012, 18:14
My Vote-Guide Book (cut down)

01-27-2012, 00:14
You'll send it home at Neel's Gap if you take it to the start. It's wasted weight.

The trail is well marked and well-worn. In contrast, there is no accurate publicly available GPS track of the trail, so how exactly will it guide your journey? The only time a GPS is useful on the trail is in town. I carried a smartphone with GPS capability that helped me find things in towns my guidebook didn't cover.

01-27-2012, 00:17
...... In contrast, there is no accurate publicly available GPS track of the trail, so how exactly will it guide your journey? .....

Hmmmm, not according to the ATC:


Guy Mott has tracks of the AT as well:


01-27-2012, 00:27
don't want to start a fight, and the computer I'm on no longer has ArcView, but I don't think a 2180 mile line in a 3.5 megabyte file is going to be accurate or high resolution. I've collected more raw data than that on a plot just a few acres in size.

01-27-2012, 00:42
don't want to start a fight, and the computer I'm on no longer has ArcView, but I don't think a 2180 mile line in a 3.5 megabyte file is going to be accurate or high resolution. I've collected more raw data than that on a plot just a few acres in size.

Would you be happy with 312,000 points? http://www.topofusion.com/at-gps.php

01-27-2012, 00:49
Thenixon is right, you will end up sending it home in Neels gap like 95% of the other people, the trail is VERY clear for 99 precent of the trail.

01-27-2012, 00:58
I'm section hiking and have used my gps on all hikes for several reasons. You can load waypoint data which has all of the shelters / trail data, mine has US topo maps, and i geocaches along the trail So I use it to look ahead at trail elevations, distances to shelters, road crossing information, it keeps track of my miles hiked for the day and trip, find geocaches along the trail, it has a compass if needed, I take all of my pictures with it, etc, etc. it's also helped me a couple of times from going off on the wrong trail and having to back track. Though the trail is marked generally well there are places which are not.

01-27-2012, 01:58
Would you be happy with 312,000 points? http://www.topofusion.com/at-gps.php

You're going to take close to five million steps. You're not ready for the rest of the math.\

01-27-2012, 02:17
Would you be happy with 312,000 points? <a href="http://www.topofusion.com/at-gps.php" target="_blank">http://www.topofusion.com/at-gps.php</a><br><br>You're going to take close to five million steps. For each point how many positions fed in to it? and did differential GPS and the global corrections feed in? What is the error at each of those 300k positions?

And does it matter? Because who is bringing a standalone GPS, which can use said positions, on their hike?

01-27-2012, 02:21
If you keep that up, Slide Rule will be your new trail name.

01-27-2012, 02:24
Oh wait, I remember this one time a year ago, I was in a mountainous area in southern NY - a bit of mountains the AT bypasses incidentally - with a GPS that boasted sub-foot accuracy on its handhel unit alone. There were places - at least 25% of the places I tried to get a fix - that even with an extra 8-ft tall backpack-mounted antenna, a system meant to boost reception and accuracy, we couldn't get a GPS fix. GPS is useless in the woods if there are mountains in the way.

01-27-2012, 02:25
I like slide rule better than the name I went by during my thru hike.

01-27-2012, 02:27
So what's your take on white blaze placement? How accurate are they really?

01-27-2012, 02:33
The blazes are on the trail. As you know, sections of the trail change every year. GPS-based shapefiles don't, they're established in the year they were taken. But even for the year that they do, I'd be surprised if they approached 50 feet in average accuracy. They'd regularly send people off the cliff, if cliffs are there.

01-27-2012, 07:42
Thenixon, i'm not saying that i don't believe you, but even the military doesn't use 8ft extension antennas for their gps systems. You may be exagerating a bit, by like oh 6ft? But you are correct, gps signal can be less than desirable in some areas due to the terrain features. However, about a good 90% of the time if I just wait 5-10 minutes without moving my gps or my smartphone for that matter will get a fix. Yes, GPS can have an accuracy error of up to 150ft, but more often than not its below 30ft, if not below 5ft. Its more about a clear view of the sky, and no so much about the terrain features arround you, but if your in a deep valley etc it will make a difference.

With a quick google search i can't find a single backpack mounted antenna thats longer than 2.5ft.

01-27-2012, 11:26
Since I put on GPS classes as part of my day job, and work with some of the biggest GPS geeks to ever carry a recreational grade GPS receiver I'll add in a little. Note: while I coordinate and attend, I don't always pay real good attention, but I'll do my best here.

The track you upload to your GPS is only as accurate as the receiver that collected it. Then, when determining where you are, the accuracy of where you're standing in relationship to where you're GPS says the trail is located is again, only as good as your receiver, antenna, and conditions locally.

Things that affect accuracy of your GPS that can’t be differentially corrected:
– Receiver noise and electromagnetic fields (like powerlines)
– Multi-path (reflecting off a car, buildings, lakes)
– Sky obstructions (like tree canopy!!! or mountains)
– User mistakes (like not holding your receiver in the proper angle to make use of the specific antenna)

So, for recreational grade GPS, and with everything being optimal, and being on Max Patch for instance, you can get accuracies plus or minus just a few feet. Under tree canopy, in a canyon, you can expect this to drop to +/- 50-75 feet or more. Still, if someone recorded the corridor within about 50 feet, and then you record your current location within about 50 feet...you should be able to see the trail if your GPS says you're right on it.

Using WAAS turned on, in good satellite configuration, and adding differential correction (both separate discussions), you can attain much higher accuracies...but tree canopy is still a huge influence.

One BIG warning: I read mention of just turning on your GPS when you need it. When you move your GPS, even just a mile or so, and then turn it on...it still thinks it's back where you last had it on. It can take a GPS receiver as long as 10 minutes to "collect an atlas" which basically means it figures out where it is now. It has to acquire tha satellites and do some ciphering and guzintas. Interpreting any outputs or locations prior to this happening will give you meaningless results.

01-27-2012, 11:36
The only time I've used my GPS while hiking was either while hiking after the sun went down or during the winter when the blazes or trails become a tad bit confusing in the snow. Literally saved my life in pin pointing a cabin while XC skiing in deep snow. Luckily I had made a waypoint earlier in the fall and was able to call upon that while the temperatures dropped into the evening (what started out as a planned 1 1/2 hour ski became 3 or 4 hours because of a heavy snow storm). With the lack of snow here in the Northeast (at least this weekend) I am planning on leaving it home while we hike instead of XC ski this weekend. Plus I will most likely have my telephone with me and not that far from civilization in Western Mass. My old eTrex Venture uses too much battery power anyway for a long trip.

01-27-2012, 11:50
Whatever the accuracy of a GPS is today it's much much better than what it was when SA was being applied, this per my father and older brother. Back then I was told only boats and planes really benefited from the use of a GPS.

04-09-2012, 00:41
Remember, you're not lost (when you have a gps). Never. Before your hike try to learn how to take the position the gps is giving you (via UTM of your current position) and transfer that to your map.