minx Posted January 10, 2003 Share Posted January 10, 2003 I'm sure this has been rehashed many times but lets talk about navigation boys and girls! GPS or no GPS? If yes which one do you have? I'm inherently cheap and have balked at dropping the coin for GPS. I'm looking forward to a couple of extended trips this year the topic has come up: is it wort the money. I've always relied on my brain and my trusty compass. (one of the few valuable things that i learned in girl scouts) However i have to admit to straying off course this summer in the Rockies. We've got one ski trip planned and some time off for extended backpacking this summer. Quote Link to comment Share on other sites More sharing options...
iain Posted January 10, 2003 Share Posted January 10, 2003 Often I do not carry a GPS when climbing due to the significant weight penalty. However if it is a lower angle snow thing and the weather is touch and go I consider it. I use an older model, the Garmin 12xl. It has a superior built-in antenna to the newer eTrex things. I had a session with the Garmin rep about this and he said to make the eTrex light and small enough, a significant amount of shielding had to be removed. The 12xl is fairly heavy, but has been a proven workhorse over the years and isn't dumbed-down with silly graphics. Â There's something nice about leaving it behind and having confidence with map and compass too. Quote Link to comment Share on other sites More sharing options...
jbclimber Posted January 10, 2003 Share Posted January 10, 2003 Well, when considering a GPS, consider this. You usually need at least a partially clear sky to lock onto satellite signals. Based upon my limited experience with my GPS, when I am hiking through the woods on a trail, the GPS is fairly useless. However, when I am above the treeline or have a partially open sky, with the GPS I can usually lock onto at least 4 satellites, which is the minimum required for an accurate position fix. So if you will be spending most of your extended trips in the woods, I don't see what the advantage of a GPS is for navigation. On the other hand, if you anticipate that you will have some opens skies, then a GPS is a great supplement to your map and compass, provided that you know how to use it and what its limitations are. Â I have the Garmin Rino 120 combination GPS/Radio, and love it. The GPS is accurate and I can upload topo maps and detailed city street maps to it. The radio feature is also good for short distance communication (less than 1 mile), like when using rock climbing belay off/on signals. Â Cheers! Quote Link to comment Share on other sites More sharing options...
sketchfest Posted January 10, 2003 Share Posted January 10, 2003 I seem to remember a TR written by Terminal Gravity, where he used his GPS on a solo climb on Rainier, during a blizzard and his account is that it worked just fine. Maybe somemodels don't have the whole clear sky issue as others? Quote Link to comment Share on other sites More sharing options...
jbclimber Posted January 10, 2003 Share Posted January 10, 2003 Well, what I mean is a sky that is clear of obstructions, not a blue sky. Trees, ridges, mountains, etc... block the signal for a GPS. Clouds, rain, and snow shouldn't block a GPS receiver from receiving signals. Quote Link to comment Share on other sites More sharing options...
sketchfest Posted January 10, 2003 Share Posted January 10, 2003 Aaahhh, that make sense. Quote Link to comment Share on other sites More sharing options...
snoboy Posted January 11, 2003 Share Posted January 11, 2003 However, when I am above the treeline or have a partially open sky, with the GPS I can usually lock onto at least 4 satellites, which is the minimum required for an accurate position fix. Â I think you only need three to get a 2D fix, and four if you want an altitude fix. GPS altitude sucks anyway, so get an altimeter, or get one with a built in alti. Â I've got a Garmin E-Trex Summit which I like a lot. I find it great for somethings, but often find that just looking at the map and some dead reckoning gets me where I want to be. Â Invaluable for deciding if you are at the "trailhead" though. Especially when driving old logging roads with no signage. Good for calling in rescue if ever that is needed. Â I also find it saves time when you are wondering if you are where you think you are. You can just whip it out and find out for sure. I've had some troubles with getting a fix, but usually can get one, even in full forest cover. Up against a hill gives me more problems. Quote Link to comment Share on other sites More sharing options...
jbclimber Posted January 11, 2003 Share Posted January 11, 2003 Yes, you can get a 2D fix with 3 satellites, however, it is not accurate. I have noticed that a 2D fix can be hundreds of feet off, so it is not very useful in my opinion. Quote Link to comment Share on other sites More sharing options...
snoboy Posted January 11, 2003 Share Posted January 11, 2003 I think that depends more on the signal quality than on the fact that there are only 3 sats involved. Of course it seems reasonable that times when you can only get 3 sats to lock on, then there probably isn't going to be good signal quality either... Â "Hundreds of feet off..." Â Let's assume 200 feet (I've never seen a accuracy reading over 100 feet off on mine) -> Â The UTM grid that we often use with GPS is based on a 1000 m square, and most of us use an abbreviated grid reference that gets us to the nearest 100m. 200 feet = 60m = less than the resolution of our "ruler"! Â If we were trying to hit a target we had been to before, and waypointed in "real time" then this innacuracy might be an issue. If we are just trying to see where on the map we are, then it's not an issue for me. Quote Link to comment Share on other sites More sharing options...
catbirdseat Posted January 11, 2003 Share Posted January 11, 2003 I have a Garmin 12 and it works well enough. I learned a hard lesson with it at Asgaard Pass. We arrived there on our way to Prussik Peak in June. It started snowing and we soon lost the line of cairns we were following. It was windy and snowing hard. Visibility was quite poor. I had not put any waypoints into the unit in advance of the trip, and my map was just a Green Trails. For one thing, GT does not have UTM markings on it. Lat-Long is practically useless. The scale is so small that small plotting errors can put you way off. My map was getting soaked as I was trying to plot our location. It sucked. Oh, we got close enough to where we wanted to camp, but we didn't know exactly where we were until morning. I learned to do my homework before taking my GPS out and to stick with USGS maps. Quote Link to comment Share on other sites More sharing options...
jbclimber Posted January 11, 2003 Share Posted January 11, 2003 Hey Snoboy: Â FYI, according to the book GPS Land Navigation, a 2D fix can be easily off by a distance of over a mile! Â And the book GPS Made Easy says that with a 2D fix, the accuracy ranges from 492-5,000 ft. Â If I get a 2D fix, I am going to ignore the postion that the GPS thinks that I am in or wait for a 3D fix. Â Â Quote Link to comment Share on other sites More sharing options...
snoboy Posted January 11, 2003 Share Posted January 11, 2003 OK... I think you may be right, and I think I know why I was thrown off the trail. Â Done a little reading, particularly this article . Â Remember, I have an eTrex Summit, which has a built in, barometric, altimeter and I always set my altitude at the start of the day if I actually think I will be using the GPS. So, the altimeter is acting as the fourth satellite in a way, and eliminating the error to a large extent. What I thought were 2D fixes were actually 3D, even though they only have three satellites. Â The article even suggests that you could get a better fix with a known altitude and three satellites, than with an unknown altitude, and four satellites. Â So perhaps the moral is to get a GPS with an altimeter... Quote Link to comment Share on other sites More sharing options...
minx Posted January 11, 2003 Author Share Posted January 11, 2003 So i think what i'm getting from this is that a GPS is a nice addition but not a mandatory item? I'm pretty handy w/my compass and a good map. GT maps suck for anything off the beaten path. Quote Link to comment Share on other sites More sharing options...
jordop Posted January 12, 2003 Share Posted January 12, 2003 GPS on icefield traverses in BC=essential (got my ass off of Columbia) GPS on most weekend tours=marginal utility as valleys on Coast are narrow enough to always have a terrain sixth sense and below treeline aint worth sqwat GPS for mountaineering=forget it Quote Link to comment Share on other sites More sharing options...
jbclimber Posted January 12, 2003 Share Posted January 12, 2003 So i think what i'm getting from this is that a GPS is a nice addition but not a mandatory item? Â Â I agree totally with this. A GPS is nice when doing cross-country trips above treeline, especially when the weather turns bad. But at least for trips in the WA Cascades and Olympics, it is not mandatory. Quote Link to comment Share on other sites More sharing options...
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