Posted in: Android, Mobile phones

Google explains the presence of a barometer in the Galaxy Nexus, hopes you’d stop asking now

The presence of a barometer inside the Galaxy Nexus raised some eyebrows, even though the Motorola Xoom has had that feature for a while now. People seemed to be having a hard time wrapping their head around the idea of having a barometer in a phone.

So to put this matter to rest and for the people to stop talking about it so much, Google’s Dan Morril posted on his Google+ account the answer to why the Galaxy Nexus has a barometer.

The answer is simple. The barometer helps the GPS to get a quicker lock on. Here’s Dan Morril explaining it in detail.

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. (Yes, you get accurate time for free if you lock on to GPS.) Because of the way GPS works, this can take a few minutes.

This goes much faster if you already have an estimate of your location. This is why “aGPS” (assisted GPS) services are so popular: by starting with a rough city-level coordinate fix through something like cell-tower network location, you can reduce the amount of math you have to do to lock on. This is where the barometer comes in.

The 3 dimensions in space are latitude, longitude… and altitude. The barometer gives you a reasonable first-cut estimate for altitude. This gives you a bit of a leg up on one of the dimensions — especially combined with “2D” aGPS — which can help speed up lock-on in general.

Now of course, the barometer can also be used for things like, well, determining atmospheric pressure (although I’m not sure it’s really weather grade.) But the main reason it’s in your phone is to help with GPS.

Thanks, Dan. Now we can all sleep peacefully at night, knowing what that barometer really does.



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