First, I am a pilot and use both the
X-Lander and
Observer for flying since they are fantastic backups for a potential altimeteror VSI (vertical speed indicator) loss -- whicih I have experienced twice. Both of these watches are unbelievably accurate altimeters and vertical speed indicators. Now, to answer your question -- Set the watdch to either a known elevation or set it to Sea Level Pressure. If you get your barometer setting from an airport (via AWOS, ATIS or ASOS) then that report is the current barometer setting in Seal Level Pressure (it is reported in inches of Hg) -- something like altimeter 30.55 or whatever. If the airport is near you and you are not in a grossly higher or lower elvation, use that report of altimeter setting (you can get these from the internet as well from the NOAA site for your area), then this is the current Sea Level Pressure for your area. The altimeter is automatically calibrated and will give you an accurater altitude reading. A pilot is always resetting the altimeter as we fly -- we are suposed to reset to the closest reporting station every 50 nautical miles. Thus, we are resetting the Sea Level Pressure to the reading of the area we are flying over so that the altimeter will read correctly. Therefore, I do the same thing with my watch -- reset to the closest (georgraphically) altimeter setting (which again is reported as Sea Level Pressure -- not absolute pressure). Conversely, you could go to a known altitude and if you set it in the watch it will automatically set the corresponding Sea Level Pressure that the watch displays.