5 ms·

> And, crucially for military applications (and unlike GPS-based systems), it is unjammable by the enemy. Is it entirely infeasible for an adversary to disrupt

> And, crucially for military applications (and unlike GPS-based systems), it is unjammable by the enemy. Is it entirely infeasible for an adversary to disrupt the local magnetic field enough to interfere with the readings?

amerine 6y ago
Based purely in my layman understanding of magnetism, you’d need quite a disturbance and that same energy would likely not make the rest of any electronics happy.
- throwaway0a5e 6y ago
  Also give away your position.
- whatshisface 6y ago
  A static magnetic field would not influence nearby electronics.
Whirl 6y ago
They could using a small EMP weapon. These happen to have short range and are explosively pumped, so at that point it’s easier to just disrupt the magnetometer by initiating rapid explosive disassembly.
contravariant 6y ago
Field strength pretty quickly drops of over distance, and even the most powerful magnets don't go much beyond 100T (and even that's a stretch). Assuming you could somehow achieve 100T 1m away from the magnet (which is charitable, usually the high teslas are only achieved at the exact centre) then just a kilometre away it will have dropped to 1 microtesla, well below the 25~65 microtesla of the Earths gravitational field. So you'd need those kinds of magnets on a kilometre spaced grid, which doesn't seem realistic. And that's with some rather charitable assumptions about building a strong magnet, to be honest I expect you'd have difficulty turning a few compasses in the same building, let alone miles away.
- chockablock 6y ago
  The AFRL press release linked in another comment says that this technique relies on measurement of the crustal magnetic field, which is in the 10s of nanoteslas range.
kurthr 6y ago
It depends on how far away they are. Magnetic (dipole) fields fall as the cube of distance. Since the earth's pole has a dipole moment (8.0 * 1022 Am^2) and is detectable ~30uT at the earth's radius, thousands of km from the core. Even a 1T field at a radius of 1m would be billion times smaller ~1nT a km away or 1/30k of the earth's field. A giant 6T MRI would be comparable to earth's field at 27m.

amerine 6y ago

Based purely in my layman understanding of magnetism, you’d need quite a disturbance and that same energy would likely not make the rest of any electronics happy.

throwaway0a5e 6y ago
Also give away your position.
whatshisface 6y ago
A static magnetic field would not influence nearby electronics.

Whirl 6y ago

They could using a small EMP weapon. These happen to have short range and are explosively pumped, so at that point it’s easier to just disrupt the magnetometer by initiating rapid explosive disassembly.

contravariant 6y ago

Field strength pretty quickly drops of over distance, and even the most powerful magnets don't go much beyond 100T (and even that's a stretch). Assuming you could somehow achieve 100T 1m away from the magnet (which is charitable, usually the high teslas are only achieved at the exact centre) then just a kilometre away it will have dropped to 1 microtesla, well below the 25~65 microtesla of the Earths gravitational field. So you'd need those kinds of magnets on a kilometre spaced grid, which doesn't seem realistic. And that's with some rather charitable assumptions about building a strong magnet, to be honest I expect you'd have difficulty turning a few compasses in the same building, let alone miles away.

chockablock 6y ago
The AFRL press release linked in another comment says that this technique relies on measurement of the crustal magnetic field, which is in the 10s of nanoteslas range.

kurthr 6y ago

It depends on how far away they are. Magnetic (dipole) fields fall as the cube of distance. Since the earth's pole has a dipole moment (8.0 * 1022 Am^2) and is detectable ~30uT at the earth's radius, thousands of km from the core. Even a 1T field at a radius of 1m would be billion times smaller ~1nT a km away or 1/30k of the earth's field. A giant 6T MRI would be comparable to earth's field at 27m.