If one needs location, then the magnetic field can be measured directly. It is already considered as a potential alternative for GPS, https://www.electronicdesi

If one needs location, then the magnetic field can be measured directly. It is already considered as a potential alternative for GPS, https://www.electronicdesign.com/markets/automation/article/21145842/electronic-design-magnetic-field-navigation-as-an-alternative-gps https://www.electronicdesign.com/markets/automation/article/... The main problem is that locally measured Earth magnetic field varies on a daily basis and is strongly influenced by solar storms. A better alternative is to use variations in Earth gravity to improve inertial navigation. That vastly more stable.