This book aims then to describe in a comprehensible way efforts made over centuries of measuring and understanding the magnetic declination. The book also highlights some important characteristics of the Earth’s magnetic field thanks to the declination measurements. Some applications and societal implications are also underlined.

Anyone living in the 21st century knows the best way to navigate is by using a smartphone App.  Decades and centuries ago, in order to find the same way a magnificent instrument was used: the compass.  Despite many being aware of the compass,...