The directional feature of Earth's geomagnetic field has been contributing to the technological development and prosperity of humankind since the invention of the magnetic compass navigation centuries ago. Today, for instance, magnetoresistance sensors are commonly used in nanosatellites and unmanned aerial vehicles for high accuracy geomagnetic…

We describe a simple experiment demonstrating the variation in magnitude of a magnetic field with distance. The method described requires only an ordinary magnetic compass and a permanent magnet. The proposed graphical analysis illustrates a unique method for deducing a general rule of magnetostatics. (Contains 1 table and 6 figures.)