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Altimeter Watches Demystified

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Your shiny new altimeter watch is cool, to be certain, but who knew watches had inch-thick instruction books? I'm there for you. I use a Vector, and the only thing I can't figure out is the stopwatch.

The Suunto Vector. You have to be smarter than your watch.

Inside your altimeter watch is a pressure sensor (a barometer) that measures changes in ambient air pressure to figure out your altitude. When you go up, the air pressure goes down and vice versa, which is why it's so hard to bake muffins in Leadville, Colorado.

But, air pressure is also affected by the weather. Dropping air pressure is typically a precursor to a storm, so we can get a decent weather prediction by seeing what the air pressure has been doing for the last couple hours. So, with two measurements working on the same sensor we've got a little trouble. If we stay at the same altitude and the weather is changing, we can get nice, accurate barometer readings. If, on the other hand, the weather stays steady and we're gaining or losing altitude, we can get a good altimeter reading.

The Nixon Delta (L) and Highgear Axis (R) do a lot of the hard work for you. Calibrate it and forget it.

But what if we're climbing a mountain and the weather is changing (read as: being miserable)? This is where the care and feeding of your altimeter comes in. Whenever you pass a point that you know the altitude of, say a benchmark on a peak, calibrate your altimeter to that altitude. (Benchmarks are typically little bronze discs stuck on rocks. The altitude and a bunch of geeky surveyor information are etched into them.)

The Suunto X9i mates an altimeter watch with a GPS to do everything but hold your map rightside up and expand instruction manuals to new and terrifying size.

Calibrating lets you get the most accurate info out of your watch. Once you calibrate it, the little computer in your watch can say "Oh, I get it. We've only actually climbed 3,000 feet, but the barometer's been dropping. Therefore we are standing at 7,250 feet above sea level and you are about to get soaked." When you start climbing again, wisely keeping your raincoat close at hand, your altimeter will give you an accurate reading on how high you are so you can brag about it later.