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aspheric_cow t1_ja9khrf wrote

Reply to comment by vwb2022 in Magnetic pole reversal by Gopokes91

> most navigational systems use some version of GPS, which aligns through satellites rather than magnetic compass

Actually no, compass and GPS can't substitute for one another. GPS tells you your location, but not your orientation. If you are standing still, GPS won't tell you which direction you are facing (or which way the front of your vehicle is pointing), but a compass can.

If you are moving, GPS can tell you which direction you are moving, but on ships, airplanes and spacecraft, the direction you are moving is not necessarily the direction your vehicle is pointing. So you still need a compass. A gyroscope also works for this, but gyroscopes drift over time, so a magnetic compass is a more accurate long-term reference.

Spacecraft often use star trackers or sun sensors for determining the orientation (attitude), but some do use magnetic sensors. And also, most satellites rely on magnetic torquers to change their attitude. Reaction wheels (aka flywheels or gyroscopes) are also used, but they eventually saturate (moving as fast as they can) and eventually they need to offload the angular momentum to something external. That something is usually a magnetic torquer, which is an electromagnet that basically pushes against the Earth's magnetic field to rotate the spacecraft. Thrusters also work for this purpose, magnetic torquers are far simpler and cheaper, so most satellites in low orbit just has magnetic torquers, not thrusters.

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vwb2022 t1_ja9ljuv wrote

Yes, modern devices use a magnetometer to determine the direction of the North. But with a GPS you know your location relative to the magnetic pole and you can determine your direction of travel using the magnetometer and software to correct the magnetic pole drift. So GPS can tell tell you your direction of travel, albeit indirectly by correcting for your position relative to the drifting magnetic pole.

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Artanthos t1_jaa0xo2 wrote

Airplanes use several different systems.

Yes, they do use gyroscopes, and they do get periodically recalibrated.

Doppler radar is another system. On airport approaches you have TACAN.

All of these systems allow the pilot to make course corrections.

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LoveandRice t1_jaakohs wrote

They do but as an air traffic controller in busy approach airspace, I will say that 70% of our instructions are headings. That would really mess up my job

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Artanthos t1_jaazdsk wrote

All my experience is on the other end.

I was an aviation electronics technician. I worked on the hardware.

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Think_Job6456 t1_jaaeu81 wrote

Is there potential for disaster involving magnets? I’m not sure to what extent they are used, if at all, in modern devices.

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aspheric_cow t1_jaesip2 wrote

No, the Earth's magnetic field is too weak to affect the operation of devices that use magnetic forces. If it disappears or reverses, things will work fine.

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