Return of the Altimeters?
Back when GG was young and scrambling up and down mountains willy-nilly, one of the gadgets he craved was an altimeter. No more trying to triangulate on peaks to figure out how close to the top of switchbacks. Or trying to locate yourself on a nondescript mountainside when in need of putting a pencil line on a map to show where a contact was.
Funny thing was, once you had one of these joys in your pocket (and GG tried both analog and digital versions), you discovered that there is a lot more that affects barometric pressure than just altitude. Sure there are weather systems, but it turns out that small pressure changes associated with winds or thunderstorms or such not would limit the accuracy. When GPS came in, the elevation errors were comparable to barometers but the horizontal errors were small enough that you could get your elevation from the position on a decent topographic map (e.g., the TopoMaps app on an iPhone works really well in this regard).
So GG was a bit puzzled to see the rumors that Apple is putting a barometer into iPhone 6s (and apparently there are Android phones with such a sensor). Really? The most likely suggestion from the comment stream is that this would be used to determine how high you were within a building, where GPS doesn’t work (other suggestions, such as group-sourced barometric pressure maps and elevation information for hiking, seem better done in many other ways). It will be interesting to see how well that pans out or if Apple has some other clever trick for such a sensor.
This all reminds GG of the special place barometers held in geology for a very long time. The initial surveys of much of the west relied on barometers to get elevations; in general, you had one barometer somewhere fixed and another on the traverse to control for weather. But when you really needed accurate elevations, barometers had limits that were hard to get past. A very hefty part of the second annual report of the U.S. Geological Survey is dedicated to the lengthy set of experiments run with barometers by G. K. Gilbert, presumably in large part to improve his measurements of the elevation of the terraces left by Lake Bonneville.
And, of course, there is the ongoing search for a successful paleobarometer. We would love to know how high some places were at different times in the past, but the only true paleobarometer proposed uses the variation in size of bubbles in basalt flows; the technique has some issues and conflicts with some other more indirect measurements.