5 ms·

Magnetic-anomaly based navigation (MagNav) is a real thing that can solve this problem, and has been shown to work with the accuracy of a few hundred meters. Pe

Magnetic-anomaly based navigation (MagNav) is a real thing that can solve this problem, and has been shown to work with the accuracy of a few hundred meters. Perhaps the government and defense contractors should look into this technology more. With a few more years of funded R&D and FAA-certification, I think its pretty likely that we'll see some of these systems on planes soon. The military is already flying with it during their exercises. disclosure - I do work on a team developing MagNav, but much of the seminal research has come out of the Air Force Institution of Technology. They performed it on an F16, paper results shown here https://ieeexplore.ieee.org/document/9506809 https://ieeexplore.ieee.org/document/9506809

mmooss 2y ago
> Air Force Institution of Technology I've never heard of that - what is it? What's it like to work with them (if you did)?
- shannonclaude 2y ago
  It's the Air Force's higher ed institution. They offer masters and PhDs. They have their own labs doing R&D.
vlovich123 2y ago
It’s not uncommon to fuse magnetometer with other sensors. We did that for indoor navigation at Apple. In fact, we had prototypes that used only magnetometer and it worked fairly well for what it was but the low update rate and poor resolution meant that it worked to like 10-30 meters which wasn’t usable for indoor by itself. Of course, for indoor there was a lot more “texture” indoors for the commercial magnetometer of the time to pick up whereas outdoor it gets trickier. Is that similar to how MagNav works just with higher quality more sensitive magnetometers?
- shannonclaude 2y ago
  So the role that magnetometers play in sensor fusion w/ IMU data is for yaw/heading/magnetic north estimation. In short, it aids your orientation (RPY estimate). However, with MagNav, they play a large role in supplying information that allows you to decrease your drift rate. https://www.sagemotion.com/blog/how-does-imu-sensor-fusion-work https://www.sagemotion.com/blog/how-does-imu-sensor-fusion-w...
  - vlovich123 2y ago
    Yes, we were doing all of that at Apple over ten years ago. I was specifically pointing out that just like WiFi has “texture” that lets you machine learn a position, so does the mag field, letting you determine an absolute position estimate purely from the magnetometer. I was wondering if the sensors and algorithms have advanced on that front.
mrandish 2y ago
I find these sorts of alternatives to what I'll call 'adversarially contested technologies' super interesting. Jamming drone control and video links is another similar instance where alternatives like MagNav could prove useful by allowing autonomous fallback operation in the case of signal loss. I assume viable solutions will probably require a fusion of approaches like MagNav, optical terrain following, laser altimeter, etc
- shannonclaude 2y ago
  We're working on making MagNav a one stop shop backup for GPS. I think to cover ALL cases however, you'll need other technologies. TERCOM, visual, and celestial all have their niche use cases. But for most cases, MagNav should do the job. Happy to answer more
  - deleted 2y ago
    [deleted]
  - mrandish 2y ago
    Well, since you were kind enough to offer... 1. Roughly how long does it take for MagNav to get a "lock". For example, GPS takes 10 or 15 seconds (at least consumer stuff I have access to). Also, with GPS the accuracy improves if you're moving. I assume it may be similar with MagNav but it would be an interesting advantage if MagNav got a lock super fast vs GPS and/or it was basically at 100% resolution without needing to move (and I understand MagNav's "100%" res is much lower than GPS). 2. What's your drive-by guesstimate on probable future evolution of MagNav tech on the 'Four Horsemen' of mobile tech (size, weight, power, cost)? For example, which of the four are more like "No reason it can't improve a lot if given sufficient time, funding and development with no new science required" and are more "Well, physics/materials are currently an unsolved, seemingly fundamental barrier to improving beyond X threshold." In a perfect world... (the one we don't live in), MagNav would be on a five year productization track that'll put it inside an Micro SD card footprint with negligible power budget at 25 cents/ea by the million and be common in small Costco drones as a fallback if GPS fails. Also, nicely appropriate username :-)
stefan_ 2y ago
If you had to break it down to the essential parts, how much would it weigh? Do you rely on having measured the area you are flying in previously?
- shannonclaude 2y ago
  Currently 20-40 pounds right now, but we're working to reduce the SWaP. MagNav does rely on having accurate magnetic anomaly maps, which the government and certain private companies have access to.
  - skywal_l 2y ago
    Are those anomalies change over time? Do you have to continuously update those devices with the latest maps?
    - shannonclaude 2y ago
      They change over geological timescales—so not anytime soon. We're talking millions of years, w/ movement of tectonic plates and such. So for right now, once an area is mapped, its mapped for good. HOWEVER. Maps may need to be redrawn if the quality of them sucks.

mmooss 2y ago

> Air Force Institution of Technology I've never heard of that - what is it? What's it like to work with them (if you did)?

shannonclaude 2y ago
It's the Air Force's higher ed institution. They offer masters and PhDs. They have their own labs doing R&D.

vlovich123 2y ago

It’s not uncommon to fuse magnetometer with other sensors. We did that for indoor navigation at Apple. In fact, we had prototypes that used only magnetometer and it worked fairly well for what it was but the low update rate and poor resolution meant that it worked to like 10-30 meters which wasn’t usable for indoor by itself. Of course, for indoor there was a lot more “texture” indoors for the commercial magnetometer of the time to pick up whereas outdoor it gets trickier. Is that similar to how MagNav works just with higher quality more sensitive magnetometers?

shannonclaude 2y ago
So the role that magnetometers play in sensor fusion w/ IMU data is for yaw/heading/magnetic north estimation. In short, it aids your orientation (RPY estimate). However, with MagNav, they play a large role in supplying information that allows you to decrease your drift rate. https://www.sagemotion.com/blog/how-does-imu-sensor-fusion-work https://www.sagemotion.com/blog/how-does-imu-sensor-fusion-w...
- vlovich123 2y ago
  Yes, we were doing all of that at Apple over ten years ago. I was specifically pointing out that just like WiFi has “texture” that lets you machine learn a position, so does the mag field, letting you determine an absolute position estimate purely from the magnetometer. I was wondering if the sensors and algorithms have advanced on that front.

mrandish 2y ago

I find these sorts of alternatives to what I'll call 'adversarially contested technologies' super interesting. Jamming drone control and video links is another similar instance where alternatives like MagNav could prove useful by allowing autonomous fallback operation in the case of signal loss. I assume viable solutions will probably require a fusion of approaches like MagNav, optical terrain following, laser altimeter, etc

shannonclaude 2y ago
We're working on making MagNav a one stop shop backup for GPS. I think to cover ALL cases however, you'll need other technologies. TERCOM, visual, and celestial all have their niche use cases. But for most cases, MagNav should do the job. Happy to answer more
- deleted 2y ago
  [deleted]
- mrandish 2y ago
  Well, since you were kind enough to offer... 1. Roughly how long does it take for MagNav to get a "lock". For example, GPS takes 10 or 15 seconds (at least consumer stuff I have access to). Also, with GPS the accuracy improves if you're moving. I assume it may be similar with MagNav but it would be an interesting advantage if MagNav got a lock super fast vs GPS and/or it was basically at 100% resolution without needing to move (and I understand MagNav's "100%" res is much lower than GPS). 2. What's your drive-by guesstimate on probable future evolution of MagNav tech on the 'Four Horsemen' of mobile tech (size, weight, power, cost)? For example, which of the four are more like "No reason it can't improve a lot if given sufficient time, funding and development with no new science required" and are more "Well, physics/materials are currently an unsolved, seemingly fundamental barrier to improving beyond X threshold." In a perfect world... (the one we don't live in), MagNav would be on a five year productization track that'll put it inside an Micro SD card footprint with negligible power budget at 25 cents/ea by the million and be common in small Costco drones as a fallback if GPS fails. Also, nicely appropriate username :-)

stefan_ 2y ago

If you had to break it down to the essential parts, how much would it weigh? Do you rely on having measured the area you are flying in previously?

shannonclaude 2y ago
Currently 20-40 pounds right now, but we're working to reduce the SWaP. MagNav does rely on having accurate magnetic anomaly maps, which the government and certain private companies have access to.
- skywal_l 2y ago
  Are those anomalies change over time? Do you have to continuously update those devices with the latest maps?
  - shannonclaude 2y ago
    They change over geological timescales—so not anytime soon. We're talking millions of years, w/ movement of tectonic plates and such. So for right now, once an area is mapped, its mapped for good. HOWEVER. Maps may need to be redrawn if the quality of them sucks.