Need help with Altimeter Settings

[sakkit]

I just got a Suunto Vector and am trying to get the correct altitude. I have a topo map of my area and my home setting is 135ft. I did a hike this a.m. to the top of a hill with a fire look-out tower on it. The topo map has this at 486ft. My final number at the top was over 1000ft. I followed the insturctions for the watch. So I was wondering if the settings need to be at zero before I start my hike. Is there another way of setting the watch? This is my first time with a toy of this kind. Thanks.
sakkit :confused:

[rickb]

What does you watch read now?

Weather changes can affect the reading-- after all your watch is nothing more than a barometer.

In my experience (with a Casio) its best to calibrate the watch to a known altitude the same day you are going to use it. That's usually frequent enough, but there are times where you would need to recalibrate a few times durring the day.

It should be quite accurate if not a lot of time has passed since you set it to a known altitude.

Rick B

[sakkit]

[QUOTE=rickboudrie]What does you watch read now?

The reading is 40ft.

sakkit

[rickb]

And whats it read now?

The number isn't so important. Point is, the reading will change even if you are sitting still. A change of 100 feet over a day or two (or even a few hundred feet) simply means that your watch is working (barometric presure is not a constant).

That said, if you KNOW that the bottom of the hill was around 200 feet and you KNOW that your watch read around 200 feet at the bottom of the hill and you KNOW that the top of the hill really was around 500 feet (a change of only 300 feet) and you KNOW that your watch read 1000 feet when you got to the top, something seems very amiss-- unless a freak weather pattern came through (like a hurricane?). Over the course of a few hours, changes in the weather should only affect your watch a little bit.

Here is what I am thinking: Either you read altitudes on your map in feet wrong (who hasn't at some time or other), or when you started your climb you watch was not recently callibrated to a known constant in feet.

Rick

[Youngblood]

Sakkit,

To restate what Rick is telling you: your altimeter is not really measuring altitude. It is measuring atmospheric pressure and trying to determine the altitude from this measurement. That is what a barometer does-- measures atmospheric pressure. Atmospheric pressure changes because of changing weather and/or changing altitude. That is why your altimeter needs to be calibrated often, so that it is indicating changes in altitude more than it is indicating changes in weather. Rick, did I get it right?

Youngblood

[Datto]

In case you didn't know already, your watch altimeter only works in non-contained environments. Altimeter readings indoors or even inside your car won't be accurate. You'd need to be outdoors for at least 15 minutes and maybe as much as an hour before the altimeter readings on your watch altimeter would be accurate.

Also note, when you look at the weather websites to see the barometric pressure for your locality, the listed barometric pressure won't be the same as the one your watch is reading. The reason is your watch is reading exact barometric pressure versus what weather stations read as 'adjusted' barometric pressure.

In case you didn't know, the temps your watch reads won't be accurate if you're wearing the watch. You have to take off your watch for at least 15 minutes and maybe up to an hour before your temp readings will be accurate. The reason for this is your body temperature while you're wearing the watch influences the temp readings on the watch.

Datto

[The Old Fhart]

Sakkit,
Good advice here. The altimeter built into digital watches are quite accurate as long as they are set at known “benchmarks.” It sound like you have done this but didn’t get the readings expected. Here is my guess on the reason.

I have the Topo USA CD set for the entire U.S. and checked the altitude at Shelburne Falls, MA. The altitude where Water Street goes under RT-112 is exactly 400 feet elevation and that seems to be the lowest spot in town. The “135” figure you used appears to be meters, not feet. Your house is 437 feet elevation. By setting the altimeter at 135 you set it 302 feet too low. The top of the hill you read as 486 is actually 1535 feet. Subtract your 302 foot starting point error from that gives 1233 feet which is probably about what you read on your altimeter.

Check the legend box on the bottom of the map and see if the units are actually meters instead of feet. If they are and you multiply the map elevation readings by 3.28 you will get the elevation readings in feet. You could also change the units displayed on your altimeter to meters just to check but it would be easier to get a map scaled in feet. Hope this helps.

[sakkit]

Sakkit,
Good advice here. The altimeter built into digital watches are quite accurate as long as they are set at known “benchmarks.” It sound like you have done this but didn’t get the readings expected. Here is my guess on the reason.

I have the Topo USA CD set for the entire U.S. and checked the altitude at Shelburne Falls, MA. The altitude where Water Street goes under RT-112 is exactly 400 feet elevation and that seems to be the lowest spot in town. The “135” figure you used appears to be meters, not feet. Your house is 437 feet elevation. By setting the altimeter at 135 you set it 302 feet too low. The top of the hill you read as 486 is actually 1535 feet. Subtract your 302 foot starting point error from that gives 1233 feet which is probably about what you read on your altimeter.

Check the legend box on the bottom of the map and see if the units are actually meters instead of feet. If they are and you multiply the map elevation readings by 3.28 you will get the elevation readings in feet. You could also change the units displayed on your altimeter to meters just to check but it would be easier to get a map scaled in feet. Hope this helps.


Thanks for the info. The numbers on the map I was using are in metric. I don't use the watch on my wrist. I clip it to my pack. This is why I love WB. The people are so helpful. Happy Hiking :)
sakkit

[grrickar]

I hate to ressurect an old thread, but do you altimeter watch gurus have any idea about the accuracy of the Nike altimeter watches?

They supposedly have a 'patented zero drift technology' to eliminate drift due to atmospheric changes. I was wondering if that is true, or just marketing hype.

There appear to be several players in the altimeter watch business: Suunto (I read they are unnecessarily complicated to use, and expensive), Nike (if their accuracy claims are true, then I guess they would be the one to buy), High Gear (a buddy of mine had the Altitech II and it worked great, but did need recalibrated once a day), and Casio.

I'm leaning towards a High Gear Summit, but might consider a Nike ACG Lance if it is more accurate.

If there is a USGS marker nearby then it would be easy to calibrate any of them, but what do you do when there is not? (I guess if you have a topo map and you are at the peak of feature or in the bottom of a gap you could adjust based on the topo map value)

[The Scribe]

I bought one from Campmor this summer and it works as all the previous posts have described. Barometric pressure. I have learned that if I calibrate it to the trailhead, it works pretty cool. It was under $30 I believe or close to it.

pcm