My experience with a mounted / handheld barometric altimeter is that the Venturi Effect causes wild swings. Equally bad (even if you wanted to stop every so often) is normal Pbar variation. I have NEVER seen ambient barometric pressure remain constant enough to believe what I see within 10'. Barometric altimeters are a marvel of sensitivity. The changes between your chest and belt are obvious if you move it back and forth a few times. My Y2Kish model fluctuates + - 2' with each read. Maybe there are better algorithms on newer models.
If I have a course where eligibility for records is at question because of the drop (rare but it does happen), I will go between the START and FINISH several times getting an average 10 reads 10 seconds apart at each place. When the difference stops changing, then (and only then) do I have confidence in what a prohibitively expensive (both time and money) surveyor would say. A lot of monkey business? Yes, so thank goodness it is rare.
Hold a barometer out a car window at 40 MPH once. This works best on snowy days
Oscar
