9 ms·

Kinda funny that the aviation industry cannot implement the more accurate inertial navigation systems (INS) right now because: "The biggest single problem in

Kinda funny that the aviation industry cannot implement the more accurate inertial navigation systems (INS) right now because: "The biggest single problem in trying to implement this change worldwide would be inertia" XD

dogma1138 5y ago
Outside of military uses when GNSS can be jammed INS is pointless when GNSS is available. INS that is accurate is very expensive to build and maintain. INS that isn’t reliant on external inputs including from a magnetic compass for calibration is even more so.
- cm2187 5y ago
  The SR71 was using stars to navigate!
  - ampdepolymerase 5y ago
    You need clear view of the sky and big lenses (you can always use more compact metamaterial lenses and infrared imaging for cloudy days but they are as expensive if not more than INS). Star charts also drift over the years and you will have the same problem as magnetic true north where the database needs to be updated regularly. Fine for airliners, not so great for skyhawks.
    - cm2187 5y ago
      Yeah I guess that wouldn’t work during takeoff and landing. But for the most common airliners (a320 to a380 and boeing equivalent): are there clouds above their cruising altitude? By day I presume you could use the sun.
      - p_l 5y ago
        Some early jetliners had special cupola for star navigation, but it soon fell out of use because NDB, VOR, DME and other radio systems were easier and better.
    - JKCalhoun 5y ago
      I'm imagining a navigation system by trying to pattern-match the earth terrain with a downward-facing camera from the plane. A suitably large database of satellite photos covering various conditions, day, night might work for all cases but cloudy (when the plane is above/in the clouds).
      - fbanon 5y ago
        Already exists: https://en.wikipedia.org/wiki/TERCOM https://en.wikipedia.org/wiki/TERCOM Since the 1950s!
        JKCalhoun 5y ago
        Oh yeah, contour-matching. I remember this being touted with regard to U.S. cruise missiles in the 80's, 90's. Guess radar + countour is more reliable than camera + imagery. (I'll crawl back to the 1800's now.)
        deleted 5y ago
        [deleted]
      - maxden 5y ago
        They've used that landing on Mars as well, Terrain Relative Navigation.
    - adolph 5y ago
      An automatic celestial navigation system for navigating both night and day by observation of K-band or H-band infrared light from multiple stars. https://patents.google.com/patent/US7349803B2/en https://patents.google.com/patent/US7349803B2/en In this celestial map, the bodies of the solar system are placed so exactly that those versed in astronomy could calculate the precession (progressively earlier occurrence) of the Pole Star for approximately the next 14,000 years. Conversely, future generations could look upon this monument and determine, if no other means were available, the exact date on which Hoover Dam was dedicated. https://www.usbr.gov/lc/hooverdam/history/essays/artwork.html https://www.usbr.gov/lc/hooverdam/history/essays/artwork.htm...
  - HPsquared 5y ago
    That worked in the SR71's case because, flying high as it did, the sky above is black and you can see stars during the day.
  - PaulHoule 5y ago
    They were teaching cadets at the Air Force Academy celestial navigation in the 1980s. This guy https://en.wikipedia.org/wiki/Guy_Murchie https://en.wikipedia.org/wiki/Guy_Murchie taught celestial navigation to navigators flying across the Atlantic in WWII.
  - adolph 5y ago
    Exactly what I was thinking about: https://www.thedrive.com/the-war-zone/17207/sr-71s-r2-d2-could-be-the-key-to-winning-future-fights-in-gps-denied-environments https://www.thedrive.com/the-war-zone/17207/sr-71s-r2-d2-cou... https://www.thedrive.com/the-war-zone/41287/r2-d2-spotted-on-scaled-composites-ares-test-jet https://www.thedrive.com/the-war-zone/41287/r2-d2-spotted-on...
- roenxi 5y ago
  If something unforeseen happens an the GNSS systems go down for whatever reason we might be set up for a terrifying few months of disruption. Coronavirus was bad enough, and most of the disruptions were voluntary to some extent.
  - p_l 5y ago
    We still have VOR network and other legacy systems. Some are no longer integrated into parts of the avionics but you can still plan routes and use them to fly. Plus Primary Surveillance Radar will see you anyway.
    - bronco21016 5y ago
      I wonder how long it will take to get the VOR network serviceable. Many of them are no longer maintained.
      - p_l 5y ago
        some dropped off maintenance, but not all. NDB is pretty much dead outside of few rare spots, though, and not everywhere had DME even at best time. But nav points used with GPS still often are based on VOR locations.
  - scoopertrooper 5y ago
    If all the various GNSS constellations went down simultaneously we'd definitely be in the shit. Not just because we lost GNSS, but we'd also probably be fighting a war or Kessler syndrome would be in effect. Either way, losing GNSS would be just one of many problems!
- ghaff 5y ago
  And even top-grade military INS does external checkpoints where possible (although it's probably pretty accurate in any case).
  - mr_overalls 5y ago
    Not saying you're wrong, but. . . who actually knows what actual top-grade INS is doing these days? Those kinds of capabilities would probably be Top Secret or SCI.
- rjsw 5y ago
  Operation Black Buck [1] was done using INS [2] as GNSS was not yet available. [1] https://en.wikipedia.org/wiki/Operation_Black_Buck https://en.wikipedia.org/wiki/Operation_Black_Buck [2] https://en.wikipedia.org/wiki/Delco_Carousel https://en.wikipedia.org/wiki/Delco_Carousel
p_l 5y ago
INS that doesn't drift pretty much immediately is expensive and needs periodic fixups, and the moment GPS became available it pretty much dropped off anyones purchase plans (as it can't be used as backup for GPS unlike VOR/DME)
- lazide 5y ago
  I think they may have been joking since INS - is inertial navigation.
- uuidgen 5y ago
  While INS is not simple, it's also not that difficult to implement. As even the cheapest drones that can hover show new MEMS sensors are accurate enough to work with a proper filtering. I did some prototype INS system as my master's thesis 10 years ago, the code was quick and dirty and even then the accuracy was like 30 meters after an hour of walking around with the device.
  - p_l 5y ago
    Thing is, it has to work over atlantic/pacific/cross north pole routes, etc. We're talking multiple hours and long distance, possibly with a lot of turbulence (even for GA, which actually gets less steady flight so...). And then it needs to provide guarantees about said navigation, guarantees that those drones do not need.
  - FabHK 5y ago
    That is surprising, you must have had an extremely accurate accelerometer and gyro, or employed tricks [1]. There are two problems with determining position from acceleration measurements: 1. You're integrating twice (acceleration to obtain velocity, then velocity to obtain position). So if you have any noise or error, you're integrating that, and integrate that again. Hello, parabola. 2. Gravity. It's strong. So you have to subtract it (as it induces an apparent acceleration upwards). If the difference between actual down and where your model thinks is down is just a fraction of a degree, you'll be totally off within minutes. See eg here: https://www.youtube.com/watch?v=C7JQ7Rpwn2k&t=1401s https://www.youtube.com/watch?v=C7JQ7Rpwn2k&t=1401s Or here: https://www.cl.cam.ac.uk//techreports/UCAM-CL-TR-696.pdf https://www.cl.cam.ac.uk//techreports/UCAM-CL-TR-696.pdf > As a concrete example consider a tilt error of just 0.05 [degrees]. This error will cause a component of the acceleration due to gravity with magnitude 0.0086 m/s2 to be projected onto the horizontal axes. This residual bias causes an error in the horizontal position which grows quadratically to 7.7 m after only 30 seconds [and thus to 770 m after 5 minutes, unless I'm mistaken, and 110 km after an hour] Or here: https://liqul.github.io/blog/assets/rotation.pdf https://liqul.github.io/blog/assets/rotation.pdf (search for "Accuracy of Velocity and Position Estimates"). [1] such as assuming that your foot has velocity zero while on the ground, which does not hold when you're in an elevator, for example, and which you can't use in a drone without some serious sensor fusion.

dogma1138 5y ago

Outside of military uses when GNSS can be jammed INS is pointless when GNSS is available. INS that is accurate is very expensive to build and maintain. INS that isn’t reliant on external inputs including from a magnetic compass for calibration is even more so.

cm2187 5y ago
The SR71 was using stars to navigate!
- ampdepolymerase 5y ago
  You need clear view of the sky and big lenses (you can always use more compact metamaterial lenses and infrared imaging for cloudy days but they are as expensive if not more than INS). Star charts also drift over the years and you will have the same problem as magnetic true north where the database needs to be updated regularly. Fine for airliners, not so great for skyhawks.
  - cm2187 5y ago
    Yeah I guess that wouldn’t work during takeoff and landing. But for the most common airliners (a320 to a380 and boeing equivalent): are there clouds above their cruising altitude? By day I presume you could use the sun.
    - p_l 5y ago
      Some early jetliners had special cupola for star navigation, but it soon fell out of use because NDB, VOR, DME and other radio systems were easier and better.
  - JKCalhoun 5y ago
    I'm imagining a navigation system by trying to pattern-match the earth terrain with a downward-facing camera from the plane. A suitably large database of satellite photos covering various conditions, day, night might work for all cases but cloudy (when the plane is above/in the clouds).
    - fbanon 5y ago
      Already exists: https://en.wikipedia.org/wiki/TERCOM https://en.wikipedia.org/wiki/TERCOM Since the 1950s!
      - JKCalhoun 5y ago
        Oh yeah, contour-matching. I remember this being touted with regard to U.S. cruise missiles in the 80's, 90's. Guess radar + countour is more reliable than camera + imagery. (I'll crawl back to the 1800's now.)
      - deleted 5y ago
        [deleted]
    - maxden 5y ago
      They've used that landing on Mars as well, Terrain Relative Navigation.
  - adolph 5y ago
    An automatic celestial navigation system for navigating both night and day by observation of K-band or H-band infrared light from multiple stars. https://patents.google.com/patent/US7349803B2/en https://patents.google.com/patent/US7349803B2/en In this celestial map, the bodies of the solar system are placed so exactly that those versed in astronomy could calculate the precession (progressively earlier occurrence) of the Pole Star for approximately the next 14,000 years. Conversely, future generations could look upon this monument and determine, if no other means were available, the exact date on which Hoover Dam was dedicated. https://www.usbr.gov/lc/hooverdam/history/essays/artwork.html https://www.usbr.gov/lc/hooverdam/history/essays/artwork.htm...
- HPsquared 5y ago
  That worked in the SR71's case because, flying high as it did, the sky above is black and you can see stars during the day.
- PaulHoule 5y ago
  They were teaching cadets at the Air Force Academy celestial navigation in the 1980s. This guy https://en.wikipedia.org/wiki/Guy_Murchie https://en.wikipedia.org/wiki/Guy_Murchie taught celestial navigation to navigators flying across the Atlantic in WWII.
- adolph 5y ago
  Exactly what I was thinking about: https://www.thedrive.com/the-war-zone/17207/sr-71s-r2-d2-could-be-the-key-to-winning-future-fights-in-gps-denied-environments https://www.thedrive.com/the-war-zone/17207/sr-71s-r2-d2-cou... https://www.thedrive.com/the-war-zone/41287/r2-d2-spotted-on-scaled-composites-ares-test-jet https://www.thedrive.com/the-war-zone/41287/r2-d2-spotted-on...
roenxi 5y ago
If something unforeseen happens an the GNSS systems go down for whatever reason we might be set up for a terrifying few months of disruption. Coronavirus was bad enough, and most of the disruptions were voluntary to some extent.
- p_l 5y ago
  We still have VOR network and other legacy systems. Some are no longer integrated into parts of the avionics but you can still plan routes and use them to fly. Plus Primary Surveillance Radar will see you anyway.
  - bronco21016 5y ago
    I wonder how long it will take to get the VOR network serviceable. Many of them are no longer maintained.
    - p_l 5y ago
      some dropped off maintenance, but not all. NDB is pretty much dead outside of few rare spots, though, and not everywhere had DME even at best time. But nav points used with GPS still often are based on VOR locations.
- scoopertrooper 5y ago
  If all the various GNSS constellations went down simultaneously we'd definitely be in the shit. Not just because we lost GNSS, but we'd also probably be fighting a war or Kessler syndrome would be in effect. Either way, losing GNSS would be just one of many problems!
ghaff 5y ago
And even top-grade military INS does external checkpoints where possible (although it's probably pretty accurate in any case).
- mr_overalls 5y ago
  Not saying you're wrong, but. . . who actually knows what actual top-grade INS is doing these days? Those kinds of capabilities would probably be Top Secret or SCI.
rjsw 5y ago
Operation Black Buck [1] was done using INS [2] as GNSS was not yet available. [1] https://en.wikipedia.org/wiki/Operation_Black_Buck https://en.wikipedia.org/wiki/Operation_Black_Buck [2] https://en.wikipedia.org/wiki/Delco_Carousel https://en.wikipedia.org/wiki/Delco_Carousel

p_l 5y ago

INS that doesn't drift pretty much immediately is expensive and needs periodic fixups, and the moment GPS became available it pretty much dropped off anyones purchase plans (as it can't be used as backup for GPS unlike VOR/DME)

lazide 5y ago
I think they may have been joking since INS - is inertial navigation.
uuidgen 5y ago
While INS is not simple, it's also not that difficult to implement. As even the cheapest drones that can hover show new MEMS sensors are accurate enough to work with a proper filtering. I did some prototype INS system as my master's thesis 10 years ago, the code was quick and dirty and even then the accuracy was like 30 meters after an hour of walking around with the device.
- p_l 5y ago
  Thing is, it has to work over atlantic/pacific/cross north pole routes, etc. We're talking multiple hours and long distance, possibly with a lot of turbulence (even for GA, which actually gets less steady flight so...). And then it needs to provide guarantees about said navigation, guarantees that those drones do not need.
- FabHK 5y ago
  That is surprising, you must have had an extremely accurate accelerometer and gyro, or employed tricks [1]. There are two problems with determining position from acceleration measurements: 1. You're integrating twice (acceleration to obtain velocity, then velocity to obtain position). So if you have any noise or error, you're integrating that, and integrate that again. Hello, parabola. 2. Gravity. It's strong. So you have to subtract it (as it induces an apparent acceleration upwards). If the difference between actual down and where your model thinks is down is just a fraction of a degree, you'll be totally off within minutes. See eg here: https://www.youtube.com/watch?v=C7JQ7Rpwn2k&t=1401s https://www.youtube.com/watch?v=C7JQ7Rpwn2k&t=1401s Or here: https://www.cl.cam.ac.uk//techreports/UCAM-CL-TR-696.pdf https://www.cl.cam.ac.uk//techreports/UCAM-CL-TR-696.pdf > As a concrete example consider a tilt error of just 0.05 [degrees]. This error will cause a component of the acceleration due to gravity with magnitude 0.0086 m/s2 to be projected onto the horizontal axes. This residual bias causes an error in the horizontal position which grows quadratically to 7.7 m after only 30 seconds [and thus to 770 m after 5 minutes, unless I'm mistaken, and 110 km after an hour] Or here: https://liqul.github.io/blog/assets/rotation.pdf https://liqul.github.io/blog/assets/rotation.pdf (search for "Accuracy of Velocity and Position Estimates"). [1] such as assuming that your foot has velocity zero while on the ground, which does not hold when you're in an elevator, for example, and which you can't use in a drone without some serious sensor fusion.