February 14, 2019
How Does Your Phone Know Which Way is North? An Explainer .
Like a lot of people, the only way I get from point A to point B is thanks to the map application on my smartphone. Map applications today primarily use your device’s GPS unit to figure out where you are and where you’re going, but your phone also gets navigational input from its magnetometer and accelerometer. Recently, your smartphone’s magnetometer may have a hard time locating the North Pole.
Our planet has two North Poles, Geographic North and Magnetic North. Geographic North is opposite the South Pole and the northernmost point on the planet. It never changes. Magnetic North is more fickle and fluctuates based on electric currents generated from the earth’s spinning molten iron core.
Predicting how our planet’s magnetic field is going to behave is no small task. Every five years, a team of scientists and geologists at the National Oceanic and Atmospheric Administration (NOAA) maps out how they expect the Earth’s magnetic field to behave. That map is called the World Magnetic Model, or the WMM, and is critical for navigation. A variety of military organizations including NATO and the Department of Defense rely on the WMM, and a piece of technology in your own pocket does too- your smartphone.
The magnetometer in your smartphone measures the Earth’s magnetic field. Then it uses the WMM to align Magnetic North to Geographic North and determines your location in relation to the magnetic field. Want to see the magnetic field for yourself? Open up the compass app on your smartphone.
Without the WMM, you could be standing at Geographic North, but your smartphone would show your location as Magnetic North, which is currently on Ellesmere Island in Northern Canada—600 miles south of Geographic North.
A recent version of the WMM was released in 2015 and would have been considered accurate until 2020, but the planet had other ideas. Magnetic North has been moving at a faster rate than the WMM forecasted, from 9.3 miles per year to 34 miles per year, or two to three miles each month. This shift, in addition to a large magnetic pulse under South America in 2016, led that version of the WMM to be declared out of date in March of 2018. Fortunately, scientists recently released an updated version before the model became too inaccurate.
The further away you are from Magnetic North, the less of an impact any discrepencies in the WMM will have on your magnetometer. So unless you plan on visiting Santa’s Workshop, your map applications will continue to work just fine. And yes, scientists are working to understand why our magnetic field is shifting at a more rapid pace.
It’s incredible when you think about it- this big blue sphere we call home can have a direct impact on the technology in your back pocket.