![Fermat's Library on Twitter: "This 1585 map by Portuguese Luis Teixeira is the first document that confirms our knowledge of Earth's magnetic field as a planetary effect. The lines on the map Fermat's Library on Twitter: "This 1585 map by Portuguese Luis Teixeira is the first document that confirms our knowledge of Earth's magnetic field as a planetary effect. The lines on the map](https://pbs.twimg.com/media/EKoI53FW4AA9IEj.jpg:large)
Fermat's Library on Twitter: "This 1585 map by Portuguese Luis Teixeira is the first document that confirms our knowledge of Earth's magnetic field as a planetary effect. The lines on the map
![electromagnetism - Digital Compass and Magnetic Declination Angle - Electrical Engineering Stack Exchange electromagnetism - Digital Compass and Magnetic Declination Angle - Electrical Engineering Stack Exchange](https://i.stack.imgur.com/WV1BK.jpg)
electromagnetism - Digital Compass and Magnetic Declination Angle - Electrical Engineering Stack Exchange
![18. Maps of magnetic declination of the MGMF nondipole part for years... | Download Scientific Diagram 18. Maps of magnetic declination of the MGMF nondipole part for years... | Download Scientific Diagram](https://www.researchgate.net/profile/Anatoly-Soloviev-2/publication/309231075/figure/download/fig8/AS:540616155435019@1505904343926/Maps-of-magnetic-declination-of-the-MGMF-nondipole-part-for-years-1900-2010-Enlarge.png)