The Basics of Electronic Compass
This page provides a basic overview of an electronic compass and explains how it has become valuable in various applications such as navigation devices.
Electronic compass is currently used in various scenes.
It is actually in a device which we use in our daily life such as smartphones and tablets.
It is used not only as a simple compass usage but also as a heading-up function* of a map in a navigation application of mobile phones.
We believe you must have had an experience of using it! With this animation, we will give you a simple explanation about what an electronic compass is.
*heading-up function: a function which can enable a map to always show the traveling direction of the user.
This is an example of a car navigation.
Car navigation utilizes GPS to show the travelling direction on the map.
When you turn at an intersection, the map will rotate so that the direction is always consistent to the where the user is heading.
This is realized by acquiring the position of the car at a regular interval using the GPS and by estimating the travelling distance and direction from a particular position.
On the other hand, in a portable device for pedestrian navigation, an electronic compass is used in addtion to the GPS.
What is the reason for this?
As a matter of fact, there is a critical difference between a pedestrian navigation and a car navigation.
Since the human walking speed is considerably slower than a car, GPS is unable to accurately estimate the walking path and hence the moving direction.
Furthermore, the GPS signal often can not reach between large buldings making it diffuclt to accurately estimate the direction.
Even if the GPS can determine the position of the user, the directon of the user can not be estimated by that alone or if the user is stationary.
So in a case where a user wants to know which way to go at a subway exit, this can not be realized by using a GPS alone.
To do this, we need an "Electronic Compass".
Just like a normal compass, an Electronic Compass can detect the geomagnetic field which will allow the device to detect the direction the user is facing even at a stationary state.
The "heading up" of a map is only possible by using an Electronic Compass in Map/Navigation applications on a portable device.
Let's recall what we studied in elementary school physics class.
We learned that the needle always points north because the Earth is like one giant magnet. Earth's geographic North pole, in actuality, exhibits a South magnetic polarity which is why the compass needle with the North polarization points to the north to show the direction.
This South polarization of the earth is called "magnetic North pole", and the magnetic field generated by the Earth's core is called "Geomagnetism".
Magnetic field lines enter the Earth’s surface at different angles depending on where you are.
At the equator the field lines are horizontal to the surface , but at the poles they are at right angles to the surface.
This means that as you get closer to the poles a compass needle will align with the dip of the field lines and thus at the poles will align vertically with the magnet field lines.
This is why a magnetic compass will point downwards when used at the magnetic north.
Earths geographic North pole is not the same as earths Magnetic North pole.
The difference between the North Pole and the Magnetic North Pole is that the former is a geographic pole with a stationary location at 90°North.
This geographic North Pole, also known as true north, is the fixed northernmost point on earth from which all points lie south.
The magnetic pole is not based on true north, but on the magnetosphere of the planet. It lies hundreds of miles (kilometers) from true north, with its exact position constantly shifting which is presumed to be the effect of the mantles and the sun.
The earth's magnetic north pole is currently situated about 11 degress from it's geographic North pole, and is in the vicinity of North Canada.
An Electronic Compass is a device which relies on the the same magnetic fields which makes your normal compass spin.
It uses a hall sensor to detect weak magnetic fields (geomagnetism) and unlike a normal compass, the hall sensor electrically measures the direction and magnitude of the magnetic field in a horizontal plane to calculate the azimuth.
A pedestrian navigation system can not be developed simply by combining GPS and an Electronic Compass.
There are several issues which needs to be considered when implementing an Electronic Compass and to measure the geomagnetic field.
For example, in portable devices, the extraneous magnetic fields are strong and subject to frequent change and distortion.
Furthermore, the levels of component magnetization may change in the strong magnetic fields often encountered around trains, stereo speakers, and other electrical equipment.
To address this issue, AKM offers the DOE (Dynamic Offset Estimation) algorithm which enables automatic adjustment of the compass for extraneous magnetic field changes, and thus eliminates the need for repeated manual adjustment.
The adjustment is automatic, efficient, and highly effective for the maintenance of accurate and reliable direction finding, whether walking along the street, getting off a bus, leaving a subway station, or passing through other environments.