A public
service announcement.
Your smartphone has a barometer/altimeter in it.
Your smartphone has a
fluxgate compass in it. It can be used to determine a
compass heading, and as a metal detector.
Your smartphone has an accelerometer in it that allows it to serve as a level, to measure heel angle, and to serve as a pocket transit.
There are various apps that combine and
record these in ways that are useful. I use Dioptra (a pocket transit with camera), "Compass Galaxy," and "Sky Map."
I would be interested in what you all have found app wise. I would especially like to find a recording barometer application that I like.