Variable vertical?

[Mumster]

My altimeter is giving me slightly variable vertical foot readings for the same trails on different days.

Today one run was 700 feet, yesterday 720. A few days ago it was 680. It doesn't vary from run-to-run during the same day, so I don't think it's just jump in the watch. I'm wondering if, when I reset settings, something changes. Does anyone know if variable barometer values or altitude when resetting can impact measurements? (It was recently recalibrated.)

[<enzo>]

I think that most altimeters will calculate vertical height based on mean atmospheric pressure at sea level. If the barometric pressure changes even just a little it will throw the reading off. Haven't got a clue how to fix that!

[M@]

I don't think you can count on much more than 50ft accuracy, which is within the measurements you quote. 50ft is pretty good for a little thing in a watch anyhow. Check the manual or whatever for the accuracy.

M@

[M@]

Holy Crap Mumster! You're almost half way to your goal and it's still 2003!

M@

[Mumster]

M@ :ma: :

Thanks for noticing. :D
I cheated by taking some time off of work to :skifemcool: . I'm only 40% of the way there -&gt; figured the goal would be impossible if I wasn't over a third of the way by the New Year :margarita: .
Three days of :atwork: , then I'm back out :skiplow: .

[Rainman]

Depending on what type of altimeter you have you may be require you to reset it frequently. Many altimeters can be affected by both barometric pressure and temperature. They do make some that take into account for these variables and adjust but all the ones I’ve seen cost over 200$. I have an analog altimeter that I picked up at REI this summer and I reset it to know altitudes as frequently as possible. Usually before I start out and when I summit mountains or reach a peak that I know the altitude of. At first I was annoyed by this but after a while it helped me to predict when it was going to rain .. or at least know the possibility of rain. One thing I noticed while backpacking is that is would change between 20 and 100 feet overnight.

[Mumster]

So, when do you get the most accurate estimate of the real vertical drop? Do high or low barometer readings account for the inaccuracy? Or change? Should I look for a rainy day, sun, or changing conditions?