https://plus.google.com/112413860260589530492/posts/jVJhPyouWDP https://plus.google.com/112413860260589530492/posts/jVJhPyou... "The primary purpose of the bar

https://plus.google.com/112413860260589530492/posts/jVJhPyouWDP https://plus.google.com/112413860260589530492/posts/jVJhPyou... "The primary purpose of the barometer is (at least, I've been told) to make GPS lockons faster. Locking on to a GPS involves numerically solving a 4-dimensional set of linear equations -- 3 dimensions in space, and time. ... The barometer gives you a reasonable first-cut estimate for altitude."