7 ms·

Naval Academy reinstates celestial navigation

80 points by aoldoni 11y ago

usrusr 11y ago
Three hours of training? Either celestial navigation is much easier than i think it is or this is exactly the sort of compromise mothers should warn their children about. I'd rather sail into a GPS outage with a one in ten chance of having a navigator trained 30 hours on board than with a 100% chance of having one trained three. And it gets better when you consider crews larger than one. Sure, we all know that decision making isn't easy, but that should not be an excuse to get away with a compromise like that.
- sfall 11y ago
  the problem persists because like any skill use it or lose it
- SamReidHughes 11y ago
  Celestial navigation is way easier than you think it is. We have accurate clocks now, and you can just take the measurements and feed it into the computer.
  - toyg 11y ago
    The point of this training today, I would expect, is that computers might not always be there.
    - gavazzy 11y ago
      We might have computers, but GPS signals can be spoofed: https://en.wikipedia.org/wiki/Spoofing_attack#GPS_Spoofing https://en.wikipedia.org/wiki/Spoofing_attack#GPS_Spoofing
      - gruez 11y ago
        Is there a reason why the signals aren't digitally signed? I understand that GPS and GLONASS was deployed over 30 years ago, but surely Galileo, with its first satellite launched 4 years ago can have this?
        Nrsolis 11y ago
        Spoofing of GPS signals isn't generally the problem the US military is most concerned about. It's availability. The assumption is that in any significant event, US space assets will be unavailable either momentarily or for some extended period. Chinese Anti-SAT weapons are one indicator that this is a likely avenue of attack for any weaker actor seeking to degrade our capabilities. So, celestial navigation is a crude but workable substitute for GPS but it has the distinct advantage of being ancient and nearly impossible to impede unless you can change the weather or the positions of the heavenly objects.
        kevinchen 11y ago
        Here's a paper that proposes GPS authentication based on signing and statistics about the signals (lots of math): http://radionavlab.ae.utexas.edu/images/stories/files/papers/nma.pdf http://radionavlab.ae.utexas.edu/images/stories/files/papers... Paper from Los Alamos with a receiver-only implementation that would use: - abnormally high signal strength - abnormally regular transmissions - a secondary time source to double-check time (e.g. NTP on a smartphone) - dead-reckoning based on accelerometers/gyroscopes/compass to double-check position http://lewisperdue.com/DieByWire/GPS-Vulnerability-LosAlamos.pdf http://lewisperdue.com/DieByWire/GPS-Vulnerability-LosAlamos...
        maaku 11y ago
        GPS signals are weak. You simply jam them.
    - knodi123 11y ago
      If the people on a modern naval ship don't have access to some kind of basic computer, then they have bigger problems than navigation.
      - showerst 11y ago
        A total blackout has happened to a US Navy Ship in recent memory: https://en.wikipedia.org/wiki/USS_Yorktown_(CG-48)#Smart_ship_testbed https://en.wikipedia.org/wiki/USS_Yorktown_(CG-48)#Smart_shi...
        knodi123 11y ago
        And when that happened, they had a bigger problem than navigation.
    - deleted 11y ago
      [deleted]
    - superuser2 11y ago
      GPS depends on satellites to stay in the right place, intact, and powered, as well as the ability to receive authentic RF signals from those satellites. Celestial navigation requires (the computational equivalent of) a graphing calculator.
privong 11y ago
This topic, though a different article, received a fair bit of discussion a month ago: https://news.ycombinator.com/item?id=10385244 https://news.ycombinator.com/item?id=10385244
engi_nerd 11y ago
Even if you don't encounter an enemy attack that disables GPS (which is not difficult), you (meaning anyone concerned with national security) should still be prepared for navigation by alternate methods when you consider how often equipment malfunctions can cause self-jamming of GPS. It's happened to me on systems that I support.
remarkEon 11y ago
If anyone has read "Ghost Fleet", this seems appropriate. However, I tend to agree with usrusr about the seemingly shallow depth of the course. http://www.amazon.com/Ghost-Fleet-Novel-Next-World/dp/0544142845 http://www.amazon.com/Ghost-Fleet-Novel-Next-World/dp/054414...
drblast 11y ago
I was in the last class to have the old celestial navigation class. It's not a difficult thing to do. You take a measurement with a sextant then consult a fifty pound book full of tables, get the two closest numbers to what you want and interpolate. There are various techniques based on time of day and the stars you can see, but if you're not doing it regularly you're going to have to look up the procedure anyway. And although you might not always be able to rely on GPS, inertial navigation, dead reckoning, and visual navigation using landmarks, celestial navigation has a huge drawback. It's defeated by cloud cover and fog.
- Retric 11y ago
  Not to be overly pedantic, but if you have an accurate timepiece you can get your longitude from averaging sunrise and sunset times. It's not particularly accurate, if you can't see the sun, but could be useful if you where otherwise lost at sea and under total cloud cover for a long period of time.
  - nocarrier 11y ago
    Do you mean latitude? I remember the days being longer in the summer when I lived at higher latitudes, but I'm having trouble seeing how you could calculate longitude by looking at sunrise/sunset.
    - stan_rogers 11y ago
      Sunrise and sunset together will give you local noon (or local midnight). Local noon plus an accurate timepiece set to a known location will give you a time offset. Knowing your time offset is equivalent to knowing your longitude (which was the whole purpose behind the Harrison chronographs). You won't know it to a tremendous accuracy, since you can't get the exact moment of sunrise or sunset, just a vague idea, your position is likely to change between sunrise and sunset, and dead reckoning on a featureless sea under a featureless sky can only be so accurate. But it's knowing the difference between local time and a reference time that gets you longitude.
    - 11y ago
ams6110 11y ago
Why not instead a "modern" digital sextant consisting of a digital camera and software. Still enables navigation by the stars (or sun) as a backup to GPS without having to spend thousands of man-hours training cadets to do it manually. And while not as accurate as GPS certainly, it would most likely be better than or at least equal to the best human navigators. You'd harden the system against EMP which is probably a standard requirement of military electronics anyway (I'd hope...)
nateberkopec 11y ago
There's a reason certain ICBMs, like Trinity, still use celestial navigation. GPS can be disabled - but the stars aren't going anywhere.
douche 11y ago
Interesting. I've been reading the Aubrey-Maturin series by Patrick O'Brian, and besides looking up what in the world spotted-dog, calipash, staysails, the various and sundry varieties of vessels, or a Magellan jacket are, there's a fair amount of old-time celestial navigation throughout - the constantly documented daily ritual aboard ship is punctuated by the daily observation of noon, and comments on the nutation(?) of the planets... It's pretty amazing how well people were able to fix their positions with such primitive instruments. I can pick out the Big Dipper at night, and figure out if I'm going east or west by the sun during the day, but that's pretty much the extent of it. I've never been out in the open sea, where I imagine you can actually see the stars well - the day-glo murk from the omnipresent streetlights blots out most of them if you are anywhere near civilization.
mark_l_watson 11y ago
Very cool. Back in the 1970s I owned a sextant that I kept on my sailboat but I don't remember how to use one anymore. GPS is great but old skills like celestial navigation and old fashioned dead reckoning get forgotten.
dabernathy89 11y ago
> The same techniques guided ancient Polynesians in the open Pacific and led Sir Ernest Shackleton to remote Antarctica, then oriented astronauts when the Apollo 12 was disabled by lightning, the techniques of celestial navigation. You'd think the proof reader would at least catch an issue in the very first sentence.
- deleted 11y ago
  [deleted]
bawana 11y ago
We will be seeing more of this kind of stuff as the world gets more complicated. Obviously, there are not enough people who know how to troubleshoot computer networks, debug poorly written legacy code and simply maintain the complex realtime systems that are used to automate buildings, boats and planes. I can imagine pilots will continue to be required on planes for this reason even though planes largely can fly themselves. Same thing with reading topo maps - a skill that all infantry will continue to need even though they have gps. In a sense, this is insurance needed to protect us from "the ghosts of Luddites'.
timonoko 11y ago
I must be the last person ever who survived thanx to sextant in 1990: I had $50 plastic sextant "Ebco". I made a program in my pocket computer (Atari Portfolio) which automatically showed your position on a map (A line perpendicular to the sun, ie with several measurements you could get a total fix). Realized however that sextant is useless if there is no horizon visible in direction of the sun. I needed "artificial horizon" but it was $1000. Too expensive. Then I saw the movie about Nansen crossing the Greenland. All he had was a bottle of mercury. He simply measured the angle between the sun and its reflection. I felt soo stupid. Then I started paddling from Vancouver city to the west in 1990. I did not understand them tides. I did not know you can get pretabulated tables. I was paddling against tides most of the time. Somewhere between Kelsey Bay and Telegraph Cove there was 2 weeks period of fog and rain. I totally lost it. I was running out of food. I decided to turn back to Kelsey. But then the setting sun peaked out and I was able get my longitude. I was 3 kilometers from Telegraph cove. Paddling back would have been a suicide. About 80 km between those places. But I was doing it against tides averaging less than 10 km per day. BTW. George Vancouver was also stuck for weeks at the same stretch of Johnstone Strait. The devilish tide current appeared to be totally random and followed none of the god-given rules and laws. https://www.flickr.com/photos/timonoko/9513772987/in/album-72157634483451516/ https://www.flickr.com/photos/timonoko/9513772987/in/album-7...

80 points by aoldoni 11y ago

Three hours of training? Either celestial navigation is much easier than i think it is or this is exactly the sort of compromise mothers should warn their children about. I'd rather sail into a GPS outage with a one in ten chance of having a navigator trained 30 hours on board than with a 100% chance of having one trained three. And it gets better when you consider crews larger than one. Sure, we all know that decision making isn't easy, but that should not be an excuse to get away with a compromise like that.

sfall 11y ago
the problem persists because like any skill use it or lose it
SamReidHughes 11y ago
Celestial navigation is way easier than you think it is. We have accurate clocks now, and you can just take the measurements and feed it into the computer.
- toyg 11y ago
  The point of this training today, I would expect, is that computers might not always be there.
  - gavazzy 11y ago
    We might have computers, but GPS signals can be spoofed: https://en.wikipedia.org/wiki/Spoofing_attack#GPS_Spoofing https://en.wikipedia.org/wiki/Spoofing_attack#GPS_Spoofing
    - gruez 11y ago
      Is there a reason why the signals aren't digitally signed? I understand that GPS and GLONASS was deployed over 30 years ago, but surely Galileo, with its first satellite launched 4 years ago can have this?
      - Nrsolis 11y ago
        Spoofing of GPS signals isn't generally the problem the US military is most concerned about. It's availability. The assumption is that in any significant event, US space assets will be unavailable either momentarily or for some extended period. Chinese Anti-SAT weapons are one indicator that this is a likely avenue of attack for any weaker actor seeking to degrade our capabilities. So, celestial navigation is a crude but workable substitute for GPS but it has the distinct advantage of being ancient and nearly impossible to impede unless you can change the weather or the positions of the heavenly objects.
      - kevinchen 11y ago
        Here's a paper that proposes GPS authentication based on signing and statistics about the signals (lots of math): http://radionavlab.ae.utexas.edu/images/stories/files/papers/nma.pdf http://radionavlab.ae.utexas.edu/images/stories/files/papers... Paper from Los Alamos with a receiver-only implementation that would use: - abnormally high signal strength - abnormally regular transmissions - a secondary time source to double-check time (e.g. NTP on a smartphone) - dead-reckoning based on accelerometers/gyroscopes/compass to double-check position http://lewisperdue.com/DieByWire/GPS-Vulnerability-LosAlamos.pdf http://lewisperdue.com/DieByWire/GPS-Vulnerability-LosAlamos...
      - maaku 11y ago
        GPS signals are weak. You simply jam them.
  - knodi123 11y ago
    If the people on a modern naval ship don't have access to some kind of basic computer, then they have bigger problems than navigation.
    - showerst 11y ago
      A total blackout has happened to a US Navy Ship in recent memory: https://en.wikipedia.org/wiki/USS_Yorktown_(CG-48)#Smart_ship_testbed https://en.wikipedia.org/wiki/USS_Yorktown_(CG-48)#Smart_shi...
      - knodi123 11y ago
        And when that happened, they had a bigger problem than navigation.
  - deleted 11y ago
    [deleted]
  - superuser2 11y ago
    GPS depends on satellites to stay in the right place, intact, and powered, as well as the ability to receive authentic RF signals from those satellites. Celestial navigation requires (the computational equivalent of) a graphing calculator.

privong 11y ago

This topic, though a different article, received a fair bit of discussion a month ago: https://news.ycombinator.com/item?id=10385244 https://news.ycombinator.com/item?id=10385244

engi_nerd 11y ago

Even if you don't encounter an enemy attack that disables GPS (which is not difficult), you (meaning anyone concerned with national security) should still be prepared for navigation by alternate methods when you consider how often equipment malfunctions can cause self-jamming of GPS. It's happened to me on systems that I support.

remarkEon 11y ago

If anyone has read "Ghost Fleet", this seems appropriate. However, I tend to agree with usrusr about the seemingly shallow depth of the course. http://www.amazon.com/Ghost-Fleet-Novel-Next-World/dp/0544142845 http://www.amazon.com/Ghost-Fleet-Novel-Next-World/dp/054414...

drblast 11y ago

I was in the last class to have the old celestial navigation class. It's not a difficult thing to do. You take a measurement with a sextant then consult a fifty pound book full of tables, get the two closest numbers to what you want and interpolate. There are various techniques based on time of day and the stars you can see, but if you're not doing it regularly you're going to have to look up the procedure anyway. And although you might not always be able to rely on GPS, inertial navigation, dead reckoning, and visual navigation using landmarks, celestial navigation has a huge drawback. It's defeated by cloud cover and fog.

Retric 11y ago
Not to be overly pedantic, but if you have an accurate timepiece you can get your longitude from averaging sunrise and sunset times. It's not particularly accurate, if you can't see the sun, but could be useful if you where otherwise lost at sea and under total cloud cover for a long period of time.
- nocarrier 11y ago
  Do you mean latitude? I remember the days being longer in the summer when I lived at higher latitudes, but I'm having trouble seeing how you could calculate longitude by looking at sunrise/sunset.
  - stan_rogers 11y ago
    Sunrise and sunset together will give you local noon (or local midnight). Local noon plus an accurate timepiece set to a known location will give you a time offset. Knowing your time offset is equivalent to knowing your longitude (which was the whole purpose behind the Harrison chronographs). You won't know it to a tremendous accuracy, since you can't get the exact moment of sunrise or sunset, just a vague idea, your position is likely to change between sunrise and sunset, and dead reckoning on a featureless sea under a featureless sky can only be so accurate. But it's knowing the difference between local time and a reference time that gets you longitude.
  - 11y ago

ams6110 11y ago

Why not instead a "modern" digital sextant consisting of a digital camera and software. Still enables navigation by the stars (or sun) as a backup to GPS without having to spend thousands of man-hours training cadets to do it manually. And while not as accurate as GPS certainly, it would most likely be better than or at least equal to the best human navigators. You'd harden the system against EMP which is probably a standard requirement of military electronics anyway (I'd hope...)

nateberkopec 11y ago

There's a reason certain ICBMs, like Trinity, still use celestial navigation. GPS can be disabled - but the stars aren't going anywhere.

douche 11y ago

Interesting. I've been reading the Aubrey-Maturin series by Patrick O'Brian, and besides looking up what in the world spotted-dog, calipash, staysails, the various and sundry varieties of vessels, or a Magellan jacket are, there's a fair amount of old-time celestial navigation throughout - the constantly documented daily ritual aboard ship is punctuated by the daily observation of noon, and comments on the nutation(?) of the planets... It's pretty amazing how well people were able to fix their positions with such primitive instruments. I can pick out the Big Dipper at night, and figure out if I'm going east or west by the sun during the day, but that's pretty much the extent of it. I've never been out in the open sea, where I imagine you can actually see the stars well - the day-glo murk from the omnipresent streetlights blots out most of them if you are anywhere near civilization.

mark_l_watson 11y ago

Very cool. Back in the 1970s I owned a sextant that I kept on my sailboat but I don't remember how to use one anymore. GPS is great but old skills like celestial navigation and old fashioned dead reckoning get forgotten.

dabernathy89 11y ago

> The same techniques guided ancient Polynesians in the open Pacific and led Sir Ernest Shackleton to remote Antarctica, then oriented astronauts when the Apollo 12 was disabled by lightning, the techniques of celestial navigation. You'd think the proof reader would at least catch an issue in the very first sentence.

deleted 11y ago
[deleted]

bawana 11y ago

We will be seeing more of this kind of stuff as the world gets more complicated. Obviously, there are not enough people who know how to troubleshoot computer networks, debug poorly written legacy code and simply maintain the complex realtime systems that are used to automate buildings, boats and planes. I can imagine pilots will continue to be required on planes for this reason even though planes largely can fly themselves. Same thing with reading topo maps - a skill that all infantry will continue to need even though they have gps. In a sense, this is insurance needed to protect us from "the ghosts of Luddites'.

timonoko 11y ago

I must be the last person ever who survived thanx to sextant in 1990: I had $50 plastic sextant "Ebco". I made a program in my pocket computer (Atari Portfolio) which automatically showed your position on a map (A line perpendicular to the sun, ie with several measurements you could get a total fix). Realized however that sextant is useless if there is no horizon visible in direction of the sun. I needed "artificial horizon" but it was $1000. Too expensive. Then I saw the movie about Nansen crossing the Greenland. All he had was a bottle of mercury. He simply measured the angle between the sun and its reflection. I felt soo stupid. Then I started paddling from Vancouver city to the west in 1990. I did not understand them tides. I did not know you can get pretabulated tables. I was paddling against tides most of the time. Somewhere between Kelsey Bay and Telegraph Cove there was 2 weeks period of fog and rain. I totally lost it. I was running out of food. I decided to turn back to Kelsey. But then the setting sun peaked out and I was able get my longitude. I was 3 kilometers from Telegraph cove. Paddling back would have been a suicide. About 80 km between those places. But I was doing it against tides averaging less than 10 km per day. BTW. George Vancouver was also stuck for weeks at the same stretch of Johnstone Strait. The devilish tide current appeared to be totally random and followed none of the god-given rules and laws. https://www.flickr.com/photos/timonoko/9513772987/in/album-72157634483451516/ https://www.flickr.com/photos/timonoko/9513772987/in/album-7...