was wondering how often one should recalibrate the altimeter. It seems it stays fairly accurate for the day, but if a change in barometric pressure comes in, the altimeter reading starts to become more inaccurate. Whats the deal?

Once a day seems to be enough unless the weather is really changing rapidly. Just set it to a known altitude while wearing it, so its temperature has adjusted to your wrist.

Cheers,

Don't forget that your altimeter is really a barometer.

I calibrate my Suunto at the beginning of each day's march. If I'm not starting at a known altitude I just wait until I reach a lake, pass, peak or any point that will give me my altitude.

Sometimes I calibrate it from the elevation on my GPS but that's not as accurate.

I took a WS4 into the woods 2 weeks ago. This was a trip starting at about 1100' hitting 5 4000+ summits and back down.

1. calibrate at car first day - walk in. Seemed to keep altitude correct
2. calibrate using topo at campsite morning. 1300'
By the time I got up to a known altitude (4200') the watch was only off 8', recalibrate. 6 hours later hit the 3rd summit and the watch was off 60'. Did not recalibrate. There was a major weather change that night, so a storm front was definitely moving in.

So, unfortunately, the watch does need re-calibrated often. I used to have an Avocet when they came out with a barometer/altimeter watch back in the early 90's which needed calibrated just as often. I was hoping things improved a bit since then.