Why does my phone have a barometer?

Starting around 2015, device manufacturers started to put barometers in phones, tablets, smart watches, and wearable fitness devices. 

These tiny, relatively inexpensive sensors measure atmospheric pressure.  Most of them are no bigger than the tip of your pinkie.  This is one of the reasons phones have vents in the bottom – to let air in so the barometer can get a reading.

What does a phone barometer do?

You may be asking, “why were barometers added to phones in the first place?”  The answer is simple:  vertical location.  Whenever you (and your device) experience a change in elevation, the barometer measures the resulting pressure difference.  That pressure difference augments the GPS data about your horizontal (x/y) location to produce a more accurate picture of where you are at any given time.

There are other potential use cases for phone barometers, including crowd-sourced weather forecasts and regular old barometer apps, but the primary reason for including this new feature was to improve the quality of geolocation data.

How does a phone barometer work?

Here’s the challenge:  on their own, barometers don’t produce enough data to accurately calculate vertical location.  That’s because changes in pressure can happen for multiple reasons.  You could be moving up in an elevator, or a storm could be rolling in.  The barometer will detect both, but can’t distinguish between the two.

To use phone barometers for their intended purpose, it’s necessary to get rid of all the background “noise” produced by the weather, leaving only the pressure readings that result from changes in elevation.  To do that, you need to compare the data coming from phone barometers against a network of local barometric pressure readings. 

Reducing noise, adding context

This is where NextNav comes in.  NextNav is deploying a nationwide network of hyperlocal weather stations powered by specialized pressure sensors.  These sensors process data from a barometer in phones by sending back data about local weather conditions, allowing the phone to “tune out” changes in pressure that aren’t related to elevation.

NextNav also puts the pressure data produced by phone barometers in context.  A simple pressure reading will tell you how high up you are against a mathematical model of the earth’s surface, but more information is required to say how high above sea level you are, or what floor of a building you might be in. 

That’s why NextNav pairs barometric pressure information with GPS location data and other surveys to produce a Height Above Terrain measurement.  This turns the Pascal readings from your device into data that can be used by delivery services, first responders, and many other applications.

NextNav’s Pinnacle service for vertical location also accounts for changes in different barometer brands.  We’ve done all the back-end work of smoothing out the subtle differences in pressure readings that make the barometers in each model of phone unique.  We’re constantly honing our algorithms to account for the unique qualities of various sensors, to the point that we’re actually starting a program to certify phone barometers against our rigorous assessment process.

Using vertical location data

With NextNav’s highly accurate vertical positioning data, first responders find people in need faster, saving lives.  Delivery services send pizzas and packages to the right place in multi-story buildings.  Rideshare passengers are picked up on the arrivals level, not the departures level on the floor above them. 

As more location apps are built with vertical location, more devices will likely incorporate barometers to produce more accurate geolocation data.  Many industrial and commercial IoT devices already contain barometers, and autonomous systems like driverless cars and drones will likely use them in the future for more accurate navigation.  Here at NextNav, we’re helping to expand this geolocation ecosystem with the help of these small (but powerful!) sensors.

Learn more about Pinnacle, NextNav’s vertical location service.