Altimeters

montezumawell · Post by **montezumawell** » Mar 12 2002 7:01 am

'What's the elevation here?' is a relatively common questions heard on the trail and on the highway, too.

There only a few ways to answer such questions: a) Map, b) Altimeter, c) GPS, d) Dial-A-Psychic, e)read the sign at the trailhead or along the highway.

Although we own and use a decent middle-of-the-model GPS, the darn thing takes forever to lock into its satellites and finally compute an elevation. We always wonder about its accuracy. Maps are great if you happen to be hiking in an area covered by a decent map (and have the map in hand). But what about altimeters?

We don't know anything about them except that they are basically barometers and supposedly must be calibrated. We know some of the HAZ members carry altimeters and are quite alti-literate. We sure would appreciate some discussion on their relative merits.

The topic has added relevance to us because on 3/11/02 we bought on Ebay a NIB Casio Men's Forester Altimeter-Barometer watch (for $39). (Note added 3/27: Rec'd the watch 3/23. Learned to use it 3/25. It stays in sync with the NWS Weather Radio barometric pressure quite well. We calibrated it at the NPS brasscap at Montezumawell and it's relatively easy to adjust elevation for changes in arometric pressure. So far, so good! More user notes soon.)

We are certain there are other, more accurate altimeters than this watch but we didn't want to be packing an altimeter in and out of our pack every time we wanted to know our elevation gain/loss. We are looking forward to your pearls of wisdom on this topic and say THANKS! for your time.

Happy Trails!

John and Susun in Rimrock

evenstarx3 · Post by **evenstarx3** » Mar 12 2002 7:22 am

I don't carry an altimeter while hiking, but just bought one for the motorhome and found that it doesn't take much change in barometric pressure to throw it off. Without moving it's shown as much as a 200 foot change in a matter of hours. Is this normal for altimeters? I know they work off barometric pressure, but I didn't think it'd be that sensitive.

joebartels · Post by **joebartels** » Mar 12 2002 9:00 am

Personally I haven't noticed that many huge changes in pressure in Arizona. I have the ninety dollar sun alt. Usually set it as I'm passing by those 4000 elevation markers on the highway on route to the hike. Or just set it at a know elevation mark of a saddle on a topo. I would NEVER count on GPS for elevation. I don't believe the hand held units respond quickly enough to be true. In all honesty... other than 'it's neat' I don't find elevation really useful. I pretty much study the topos until I go blind these days before heading out on a hike. Then again if I was in CA or CO I'd probably use it more.

Sid & ck1 have a thread on the watches. May be on the old board though.

Fritzski · Post by **Fritzski** » Mar 12 2002 3:34 pm

In my business the barometric pressure used for setting your altimeter is crucial and we therefore basically get up to the minute readings. The pressure can and does swing widely here in Arizona as it does in all places, but due to the high pressure systems that dominate the area and the lack of storms, it tends to do so less often.

I agree with Joe in that I'm not sure what difference a couple hundred feet would really make to a hiker anyway. As he says, the only sensible way for a hiker to calibrate one is to set it to a known elevation. Like him, I don't pay that much attention to elevation. Most mapping software provides a 'profile' view of the route which shows prominent peaks and valleys which I sometimes find helpful.

I do disagree though on the accuracy of a GPS. My hand held unit tracks up to twelve satellites simultaneously and the triangulation available from that many points can be very accurate.

Your unit should take a few minutes to lock on when starting at a new location, but after that it should only take less than a minute. If it takes much longer than that I'd take it back. Other than that, if you don't mind burning a couple batteries, just leave the unit on and let it continuously track.

montezumawell · Post by **montezumawell** » Mar 12 2002 6:20 pm

Thanks for the posts so far. Some points of clarification. We don't have mapping software and don't plan to get it. The altimeter won't be used much in AZ but will probably get a lot use during our upcoming 6 months in the Utah moutains this spring, summer, and fall. Our GPS sucks batteries like kids gobbling cotton candy at a carnival. Since we do hike a lot and are on a sort of fixed income, AA battery cost IS an issue. Hence the Casio with the 3-year battery life. Joe's use of roadside elevation markers is a good tip. I know we will be seeking out known survey benchmarks as well. Any other calibration tips? (Note added 3/27: The Casio adjusts in 20 foot increments. In effect, the altimeter is simply an 'adjunct' barometer. The barometer is more important to view (overall) than the altimeter. If the barometric pressure is changing rapidly, the altimeter's reading are going to be haywire for sure! The nice thing about the Casio is the barometric pressure trend graph. This graph displays at least the last 18 hours of change in a crude sort of x-y bar chart. Crude but effective. Watching this chart has really helped us make sense of the altimeter. More later as we figure it out.)
J&S in RR

BoyNhisDog · Post by **BoyNhisDog** » Mar 12 2002 6:48 pm

We have used GPS for navagation in our airplane for years but have never relied upon it for an altimeter. With a ground station it is very accurate but with satalites alone it is not. I can't tell you how far off it is but we have to have accuracy. The same goes with setting our Altimeter. We get an update every hour. It is possible to be 400' off easy. I have seen it happen. Usually it is much less though.

Cakewalk · Post by **Cakewalk** » Mar 13 2002 8:22 pm

When I hiked Quartz Peak with AZHiker99 last fall He had a casio watch with altimeter built in. If I remember correctly, It would show an elevation change every 100 feet.

He said He got it at the casio store in Arizona Mills mall for less than $100.

ck_1 · Post by **ck_1** » Mar 14 2002 1:09 am

Syd and I discussed this before the webswitchthing....

I wear a Suunto Advisor wristtop computer....big watch, cool gadgets. It has a barometer/altimeter/heartrate monitor/digital compass/temperature/time/date///////

I have found it to be dead on accurate. I monitor it occasionally at home and notice that the alti will fluctuate within 100 feet. The different fronts do effect its accuracy. Anytime you travel more than about 100 miles, you need to check that it is accurate...I do as Joe does by using roadside markers or, the trailhead elevation if given in my info for the trails.

The advisor allows me to set the rate at which it will 'read' the altitude. The option comes in handy when switching from hiking to mountain biking, as with the increased speed, you're going to want the watch to register alti at a faster rate than hiking...I can provide more detail if needed.

I'm still learning how to use mine...I generally hike with a topo, and have found a small sense of accomplishment when I can successfully locate myself on the trail based upon the contour and the alti.

montezumawell · Post by **montezumawell** » Apr 14 2002 7:25 pm

Well, we finally had a chance to really put our new Casio Forester altimeter through a pretty decent series of field trials. We did five day hikes up at the South Rim betwen April 8-13. Where else could you find so many well known and documented elevations? Not only that but the NPS partnered with the NWS to put a weather radio repeater up there so you can get hourly barometric pressure readings, too.

Put simply, we were absolutely amazed at the Casio's pinpoint accuracy.
Even as several weak weather systems moved through and changed the barometric pressure, the altimeter hung tough and rendered really accurate readings. Since you hike down and then back up, you have a chance to verify its readings at the beginning, middle and end of each hike. Awesome accuracy! We literally stumbled on a USGS brass cap benchmark while walking the Rim Trail and, sure enough, the altimeter matched the 'chiseled in brass' elevation put there decades ago.

We last looked at the altimeter Saturday about lunchtime out at Lipan Point after day hiking a portion of the Tanner Trail. It matched the TH signboard elevation and we didn't give it another thought. We drove out past Desert View and on to Cameron toward Flagstaff. As most of you know, there's a highway elevation marker of 7,276 feet when you top out of that long climb up from Deadman's Wash toward the Peaks. We happened to casually glance at the altimeter then and it registered 7,280. We both about fainted!

Sure, enough, after all those ups and downs from Lipan to Rimrock, the altimeter showed our correct home elevation when we arrived back at the house. For a $39 object, this is pretty impressive.

We're not into promoting any particular business but if you want to know where we bought this Casio on Ebay, you can send us a PM and we will pass along the seller's Ebay ID. He sells them on a fairly regular basis.

Well, that pretty well closes our input on this topic. We sure appreciate all of your thoughts and comments and we are very gratified that you all have helped us understand what to expect out of one of these, as well as how to use it, too. THANKS!

ck_1 · Post by **ck_1** » Apr 15 2002 2:48 pm

Thanks for letting us know what happend with both this and the pedometers....

Donald · Post by **Donald** » Apr 16 2002 10:41 am

Even as several weak weather systems moved through and changed the barometric pressure, the altimeter hung tough and rendered really accurate readings.

I understand how a GPS might be able to tell the altitude independant of the barometric pressure, but how does the Casio do it?

In Ron Hood's Solo video he used a Talk-About Motorola type radio which measured the altitude, but it was certainly affected by the barometric pressure. In fact, one of the uses he made of this has not been explicitly mentioned here. If one takes an altitude reading and it dramatically changes without you moving much, then it might be indicative of an approaching storm, for which one might need to prepare.

I came back to add that I have seen a SAK with one built in, but I am not sure I would want to trust having one continue to work in a knife. Perhaps they seal it really well.

In, Through the Brazilian Wilderness by Theodore Roosevelt, ©1914, the President made use of an altimeter/barometer. As I dimly recall it was helpful in negotiating the rapids, in telling how fast the altitude changed, and when they would have descended, to get a rough idea as to location.

Thanks for the info. on how the Casio performed.

Altimeters

Altimeters

Keep those notes coming!

Casio Forester really works well