Is there a way to measure the force of magnetic north (as on a compass)?

Question

I know that a simple compass will point to magnetic north. Is there a way to measure that particular force, to determine its actual strength?

(I am assuming it is not a constant strength globally.)

Answer 1

A simple compass, in the absence of artificial fields, will indeed point to magnetic north.

One can measure the intensity of the Earth's magneitc field by, off the top-of-my-head, putting a suitable indicator (a compass would be fine) in the middle of a solenoid coil. Then, by driving the solenoid from a DC power supply, find the current that makes a magnetic field that exactly cancels that of the Earth. The compass will then wander randomly - a little math, some basic measurements of the solenoid (radius, number of turns), and you'll have the field intensity of the earth.