Magsail – Earth magnetism

The Magsail program aims to equip sailboats with magnetometers to measure the magnetic field on sea.

Earth has a strong magnetic field produced by the liquid outer core, essential for life on this planet.  Indeed, it plays the role of a shield that protects the Earth against high-energy particles from the sun. The presence of a terrestrial magnetic field is indicated by different phenomena which can be observed on Earth : the compass needle pointing the north, polar auroras (borealis or australis), or even the migration of some particular species of bird or fish !

Context and challenges

The strength of the magnetic field and its direction (position of the geomagnetic poles) change over time. Some specific rocks essentially volcanic, which means formed by rapid cooling of magma on the surface (for exemple this is the case for basalts which are found in the oceanic crust), have the ability to record the magnetic field when they are formed. Indeed, when ferromagnetic minerals solidify they shift towards the magnetic north, and the rock will acquire a magnetization equals to the intensity of the terrestrial magnetic field at the time of its formation. The study of this “fossilized” magnetic field has shown that geomagnetic poles have been reversed  periodically over time. We find these polarity transitions as magnetic anomalies, particularly on the oceanic crust, which have allowed to demonstrate the plate tectonics theory !

These data will be used by researchers involved in the program, and will be made available on a international data base.



  • Date the ocean floor thanks to the magnetic isochronal anomalies
  • Get information about the oceanic crustal structure (seamounts, basins, ridges, fracture zones, …)
  • Get information about the nature of the crust composition (oceanic and continental)
  • Generate a magnetic worldwide data base, as the current map is still incomplete in the maritime area.
  • Constrain better the global models of magnetic terrestrial field (IGRF, …)

This information is essential to constrain better the cinematic reconstruction models of the movements of tectonic plates, and the evolution of the continents since the fragmentation of the supercontinent, the Pangaea, more than 200 millions years ago.


  • Enable citizens to improve their understanding the functioning of the Earth and its dynamics.
  • Enable citizens to reconnect with sciences and with current research programs, by participating in the acquisition data.

Measuring kit

The idea is to develop a kit composed by a magnetic sensor which records the intensity of the magnetic field according to 3 components, and to couple it to an electronic gyroscope. By this way, the sensor can be orientated in the space to determine the direction of the magnetic field and it enables to interpret better the observed anomalies (structural, shapes,…). The kit will be also equipped with a GPS to get the time and the position of each measurement. The data will be stored on a SD card.

How it works ?

The first step will focus on fix the kit in a strategic point to limit the magnetical influence of the boat (magnetization of the hull, metal objects, electronic,…)

It will also be necessary to calibrate the sensor to correct the influence of the boat trajectory on the magnetic measurements. To do this, the boat will achieve a “8” trajectory to move the sensors in all directions, which allow to correct the measurements by making the standard insensitive to the boat direction.

Then, the sensor will be ready to operate, with a simple switch to turn it on and occasionally a quick check on the green light which indicate a good operating, and let’s go for adventure!

The data will be acquired continuously and automatically during the navigation.

Finally, data will be recovered in the 6 months/ 1 year after the acquisition, at the end of the travel for exemple.

Programm status

Programme in creation.
Development of a prototype coming soon.

Scientific partners

Programme built with the IPGP laboratory (France), and others in the course of partnership.

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