How compass apps can tell direction..??
If you were to go back in history and meet with the explorers and
navigators of yesteryear, they would probably be wielding — at least one
— magnetic compass. Whip out your compass app on your smartphone, and
they’d probably be flabbergasted — well, with that and your time
machine. But how has the compass worked to help everyone from ancient
Chinese seafarers to today’s Boy Scouts of America? And how exactly does
that timeworn technology work in your iPhone?
First, we’ll go over the magnetic compass. This trustworthy piece of
equipment has been around since 200 BCE, according to William Lowrie, a
professor emeritus at ETH Zurich. Navigators started using this compass
regularly on land and sea closer to 1000 CE, in present-day China. The
standard magnetic compass of the 20th century is made up of a magnetized
needle in its heart with a face showing cardinal directions — north,
south, east, and west. The needle is mounted on a surface with low
friction so that it can easily turn; if held flat, one end of the needle
will point toward magnetic north and one to magnetic south.
The compass is able to determine north and south due to the magnet’s
interaction with the Earth’s magnetic field. The cause of the magnetic
field is not completely known, but geologists have made hypotheses
regarding the phenomenon by analyzing the layers of the Earth. The Earth
is made up of an outer crust, followed by the upper mantle, the inner
mantle, the outer core, and then finally the inner core at the very
center. The inner core is made up mostly of molten iron, but the very
center of the inner core is under so much pressure that the iron becomes
solid, according to howstuffworks.com. It is believed that the rotation
of the Earth and the immense heat from the core cause the iron to move
in a rotational pattern. This rotational pattern may be the source of
the magnetic field that we see on Earth. The field produced is very
weak, however, which is why the needle on the compass needs to be very
lightweight and on a surface with minimal friction.
As expected with any technology created over two millenniums ago, the
compass has its issues. First, it has to be completely level to work —
making it rather difficult to use on something like an airplane. Also, a
magnetic compass can take a long time to correct itself. Another
confusing thing is that the magnetic north pole is actually the
geographical south pole (and vice-versa).
So if the traditional needle compass works because of a small magnet,
how do the compass apps in phones work? As it turns out, the
smartphones do have a small magnetometer, which can measure the Earth’s
magnetic field. This information is combined with an accelerator inside
the phone. The accelerator gets information regarding the phone’s
position in space. It is able to pinpoint the phone’s position from
solid-state sensors within the phone that can measure their tilt and
movement. The information provided by these devices means that the
compass app can display cardinal directions no matter which orientation
the phone is in, according to the algorithmic software development
company Sensor Platforms.
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