This post is intended to address quite a few questions on this forum. I use the
Observer and
X-lander for backup instruments (altimeter, vertical speed indicator and compass0 despite having a
GPS unit. If my electrical systems goes, so does my
GPS. See also my reply below to "
Observer Virgin": The altimeter can only be as precise as the current Sea Level Pressure you set in the watch. You can get these settings from your local airport. BUT, these settings often change over short periods of time depending upon the movement of high and low pressure systems. For flying, we want to be sure we have input even small changes in barometer (altimeter) settings. For everyday use, setting it once a day will likely suffice except when the weather is changing rapidly (fast moving lows or highs). You cannot determine the alititude of a commercial aircraft since teh cabin is pressurized (to about a Sea Level pressure of 5000 ft.) It is useful to me since I am flying a non-pressurized aircraft. I have found my
Suuntos to be unbelievably accurate for both alltitude and vertical speed indications as well as magnetic bearing. They are fantastic whatches! My son who is also a pilot is also amazed at their accuracy -- but you need to know how to use them correctly for setting Sea Level Pressure. When bush flying we don't have access to an altimeter setting, but we can ascertain altitude. So, we set altitude(of ouor landing location) in the watch and Sea Level Pressure is automatiically determined and set by the watch. Thus, the watch altimeter will be accurate as a result.