August 19, 2011. Bill Szydlowski
credit: JametiksAnalog and digital compass watches are quite easy to tell apart. They do look different from one another.
An analog compass will have the typical needle and letters for the direction in a circular frame. On the other hand, a digital compass will mostly be just numbers from 0 to 360 degrees.
Aside from their appearance, they work in a different way. People who need a highly accurate compass are really better off with an analog one because digital compass readings can be off by 11 degrees.
Magnetic fields and distortions
The Earth’s magnetic field is what makes an analog compass work. Actually, any compass will rely on the Earth’s magnetic field in order to work. However, digital compasses make use of electronic sensors rather than a floating needle.
The sensors that digital compasses have are subject to other forms of magnetic distortions. There are actually two types of magnetic distortions. These are referred to as hard iron and soft iron effects.
Hard iron distortions occur because of permanent magnets. It can also be caused by magnetized metals like iron or steel. This can already cause inaccurate readings.
On the other hand, soft iron distortions are caused by the interaction of the Earth’s magnetic field and the magnetically soft material around the compass. In order to make the compass more accurate steer clear of such magnetic or metallic objects.
Why are compasses calibrated?
In order to get more accurate readings, the magnetic distortions in the area must be taken into consideration. An offset is usually subtracted from the initial compass reading. This can only be done per area. Different places may have other forms of magnetic distortion. Thus, calibrating the compass again is needed.
Anyone can still use a compass without any calibration for repeatability. This can work if accuracy is not such a big issue. Barometer watches with digital compasses may also need to be calibrated. The user manual can inform the watch owner how to go about it.
Published August 19, 2011. Bill Szydlowski
