[pct-l] altimeters

[mark v]

Altimeters aren't that smart.  They don't differentiate, because they solely base elevation on pressure change.  That doesn't mean they're as useless as some think, and definitely if you keep an open mind and do some math in the first few weeks on the trail, you can yourself make up for how smart your altimeter isn't.  

E.g.  All altimeters,  when ascending in high pressure weather (clear skies), will slightly underestimate your ascent.  Just how much depends on your particular altimeter and ascent rate.  I figured within a few days that mine was consistenly about 5% lacking.  If i ascended 1000 ft., it would tell me i had only ascended 950 ft.  The one i had previously had a bigger difference.  If the weather CHANGED from low pressure to high pressure, the difference approached 15% even.  And if rain moved in, of course the %s were the opposite.  

This all reminds me of a story of another hiker bitterly convinced i was wrong about where we were in the southern sierra, because his altimeter told him he was at xxxx', when really we were at xxxx'+5%.