Altimeters
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spelt with a t
(spelt) - F

Locale: SW/C PA
Altimeters on 09/27/2012 12:01:50 MDT Print View

I'm curious how many people use altimeters regularly in navigation, particularly in lower, wooded mountains like the Appalachians, where long distance visibility often isn't good, but the total elevation difference might only be a few thousand feet.

Joseph R
(Dianoda) - MLife

Locale: Chicago, IL
Re: Altimeters on 09/27/2012 12:30:28 MDT Print View

Sometimes I bring a Highgear Axio ABC watch and attach it the chest strap on my pack to augment my awareness of altitude, and use it as an always-on source of relatively accurate altitude information. I find it works best when recalibrated frequently, which I do in the field using my phone's built-in GPS (I use a backcountry navigation app to load offline topo maps to the phone for each trip). Depending on signal, GPS is typically accurate to within a 100ft for altitude, and I generally compare the calibration of the altimeter to the GPS result each time I check my position.

Edited by Dianoda on 09/27/2012 12:31:34 MDT.

spelt with a t
(spelt) - F

Locale: SW/C PA
Re: Re: Altimeters on 09/27/2012 12:53:01 MDT Print View

Hm. Well, I don't use a GPS, and I don't wear a watch, so I imagine it'd be best to get a standalone altimeter (if I do). Calibration is something I have wondered about. It's my observation that the cheaper altimeter watches are never praised for their accuracy, which leads me to believe any cheap digital unit isn't going to be very good and I should be looking at analog models. But I have no experience with them, either.

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: Re: Re: Altimeters on 09/27/2012 13:00:36 MDT Print View

For altimeters based on air pressure, you have to calibrate it at the start of your hike, because the air pressure varies with time, but over the course of one hike it stays pretty much the same, unless a storm system blows in right when you're hiking.

So, you have to know the altitude of your start point, or some point on the way. Or you can re-calibrate if you get to a place with known elevation.

Kevin Babione
(KBabione) - MLife

Locale: Pennsylvania
Watch Altimeter on 09/27/2012 13:15:47 MDT Print View

As posted above, the big thing to keep in mind with a pressure altimeter is the assumption that the weather hasn't changed.

I have a Nike watch with built-in compass, thermometer, and altimeter and one of the cool features is called "Ski Stopwatch" (or something like that). Basically what you do is to let it know the altitude of the end of the ski run (by pushing a button) and then you start the Ski Stopwatch at the top of your run. When you reach the base altitude it automatically stops the stopwatch.

It works because on a given day on the mountain there's probably not going to be a significant change in the surrounding barometric pressure.

When I'm hiking in the mountains of PA (okay, hills to those of you out West) I'm usually able to eyeball where I am on a topo map by estimating how far I've climbed since the last "bottom" and/or how far I am from the top.

mik matra
(mikmik) - M

Locale: Allways on the move
Re: Altimeters on 09/27/2012 13:55:39 MDT Print View

We almost always go on walks to areas where a trail is grade 5. Here in Oz grade 5 means that the trail 'might not' be plain to see. I can vouch for this as most of the time (over 90%) there is no trail as such. It almost seems like the easiest way according to gradients and geological obstacles. So in aid of this we always take a topographical map and a GPS. We try to do our best without the GPS, reading the land and deciding on best way to tackle an obstacle and such. To be honest using/relying on the GPS is almost never about our altitude but rather our positioning. If we are aiming at getting to the top of a mountain peak or somewhere with a definite altitude reading it is good to check on the GPS to see how much further we have to 'climb' vertically to gauge your effort compare to how much daylight we have left.

Just don't buy a cheap altimeter. One of my mates bought a $20 special off Ebay. As soon as it was in my hands I could tell the cheapness of the thing. We climbed for an hour and it still read the same altitude. I know it could be a difference in air pressure but we were on a sharp incline and I am having trouble accepting that the atmospheric pressure would have been changing that fast to keep the same altitude reading as 15om elevation difference from before.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Altimeters on 09/27/2012 15:40:19 MDT Print View

All the time in the mountains. In fact, we often get our position just from the altimeter and the map. We are on 'that' spur, and at 1,500 m. Easy.

Yes, you have to track pressure changes each day, but that's not hard.

Cheers

Dave Heiss
(DaveHeiss) - M

Locale: Pacific Northwest
Axio altimeter on 09/27/2012 16:24:45 MDT Print View

I like using an altimeter to gauge my progress on climbs up to or down from passes, etc ("hey, I've only got 400' to go!") and like Roger said they come in handy when used in combination with a topo map to quickly see where you are. I've been using the Axio Mini. It wasn't expensive, seems accurate, it's a nice small size, and I usually hang it on a shoulder strap and keep it on the display mode that shows altitude, time, and temperature.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Altimeters on 09/28/2012 02:24:45 MDT Print View

GPS may or may not be really good for altitude determination. For one thing, you are using a civilian GPS receiver, and it is not as good as a military version. If you have very good satellite geometry and very good view of the sky, then the very best vertical accuracy that you can expect is 1.5 times the horizontal accuracy. Many GPS receivers will tell you the estimated horizontal accuracy. However, if you do not have good satellite geometry and if your view of the sky is sketchy, the vertical accuracy might be several times worse than the best expected. Some GPS receivers have an internal integrated barometric altimeter, so you can use the barometer to calibrate the GPS altitude or vice-versa.

--B.G.--