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Re: how accurate is the barometer and the thermometer?

First you must start with a known altitude, or a starting reference point. From there, you can measure the change in altitude relative to that point, accepting that you're also factoring in changes due to weather conditions. The latter part is very important and affects all pressure-based altitude calculations equally, including the Suunto (they do offer more features such as enhanced reporting resolution and conveniences such as altitude lock, but do not have more inherent accuracy in the sensor).
This is probably the most important part to keep in mind - it's really not a question of accuracy of the sensors - my Protreks and my Suunto show the same absolute pressure. But the implementation is very different. I got great results while on vacation just a few days ago by using the logging feature of my PAW-500. I started the recording session when leaving my home - 1st calibrating the altimeter of course. Then stopped the session when reaching my destination - all I then did was to recalibrate to the last recorded altitude stored in memory when travelling back - reaching home again the height was correct within a range of +/-5m. My Suunto X-Lander can't do any better (of course it doesn't have alti-lock either). Still I wish they at least would implement MSLP - then I can live just fine without the alti-lock (just takes a little more effort in calibrating). I have to say however that the altimeter in the X-Lander updates faster than the one in the PAW-500 - tried it once while travelling by car (I was not the driver :-d) and having one on the left and one on the right wrist.

cheers, Sedi :)
 

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Re: how accurate is the barometer and the thermometer?

They also have sealevel compensation - which basically just is a calculation of what the air pressure would be at sealevel, despite one being up in, say, the mountains. The major advantage of this, is they can be easier to calibate - provided one have the actual local sealevel pressure from another source.
You can also calibrate it using a know altitude and it will then calculate the current sea-level pressure based on absolute pressure and temperature. So you need only either one of those values to calibrate it exactly.

cheers, Sedi :)
 
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