How does an electric compass work?

General Questions
#1

I came across a small pocket digital readout compass the other day. It appeared to be completely electronic, with no moving parts.

How is this thing measuring the magnetic field, and determining its polarity?

#2

The subject you want to look up is “Hall Effect”:

http://www.britannica.com/bcom/eb/article/3/0,5716,39723+1,00.html

Now, what I want to know is why the little handheld hiker’s gps unit I have can’t incorporate a digital compass as well.

#3

vb’s parser thinks the commas are terminators:

try this