10 ms·

Seeing stars again: Naval Academy reinstates celestial navigation

99 points by curtis 11y ago

gchadwick 11y ago
I wonder if they also asked trained officers to do regular practise? The theory behind celestial navigation is fairly trivial (I've almost forgotten it all but give me an alamnac and an hour and I'm confident I'd work it all out). The successful use of a sextant for a decent fix however requires training, practise and regular use to keep your skills sharp.
- gchadwick 11y ago
  > But it's only three hours of celestial navigation — so students won't be skilled with sextants. Looks like they won't even get a sextant out of its box
- Tepix 11y ago
  Moxie Marlinspike's documentary "Hold fast" (2010) [1] inspired me to learn how to use a sextant. Most of the sextants you can get on eBay these days are just for decoration, however. [1] "Hold Fast: Stories of maniac sailors, anarchist castaways, and the voyage of the S/V Pestilence..." https://vimeo.com/15351476 https://vimeo.com/15351476
  - Luc 11y ago
    > Most of the sextants you can get on eBay these days are just for decoration, however. Ugh, these things are a plague. There's a factory in India pumping out most of these. They do a whole bunch of variations, boxes, antiquing, etc. Some sellers on eBay list them as genuine antique instruments, which is straight up deception. The replicas of box sextants (small pocket instruments in the shape of a round box) are especially hard to spot if the seller is dishonest.
- sizzzzlerz 11y ago
  Its also one thing, taking a sight on land but a whole other thing doing it on the ocean when the ship is rockin' and rollin'. That takes practice, too.
yread 11y ago
RYA Yachtmaster course requires celestial navigation and some schools even require candidates to perform the navigation on the qualifying passage (couple hundred nm) without GPS.
- gchadwick 11y ago
  It's the Yachtmaster Ocean, and as far as I know you're allowed to use GPS on your qualifying passage you simply have to take some sights whilst on passage to present to the examiner. I think they also allow for cloudy weather preventing any sights from being taken and allow you to present some from another trip. There's some controversy there too as to whether it should be left in the syllabus. Personally I think it's a nice thing to do, there's something very pleasing about producing a fix especially when you do fun things like producing a running fix from sun and moon sights.
  - Robadob 11y ago
    > I think they also allow for cloudy weather preventing any sights from being taken Is there not a modern equivalent of the medieval 'sun stone'? https://en.wikipedia.org/wiki/Sunstone_(medieval) https://en.wikipedia.org/wiki/Sunstone_(medieval)
    - sethrin 11y ago
      Knowing the direction of the sun to within a few degrees is unlikely to help much. For one thing, you have no other "fix", and for another, an error factor of a few degrees probably represents an error of a few hundred (nautical) miles. You should probably read a bit more about celestial navigation to understand the problem.
xg15 11y ago
I wonder if, with the use of image analysis, it would be possible to create a "robo-sextant" - i.e. a system which scans the sky in certain intervals, locates the waterline, sun or other celestial bodies and performs the necessary calculations. Such a system could be used to e.g. detect GPS manipulation quickly
- dagw 11y ago
  It's an idea that has been around for awhile: http://www.ri.cmu.edu/pub_files/pub2/cozman_fabio_1995_1/cozman_fabio_1995_1.pdf http://www.ri.cmu.edu/pub_files/pub2/cozman_fabio_1995_1/coz... is just one of dozens of papers covering the idea. There even appears to be a patent on the idea: https://www.google.com/patents/US7706917 https://www.google.com/patents/US7706917
  - Ao7bei3s 11y ago
    It has actually been done: the SR-71 Blackbird had one. https://en.wikipedia.org/wiki/Lockheed_SR-71_Blackbird#Astro-Inertial_Navigation_System https://en.wikipedia.org/wiki/Lockheed_SR-71_Blackbird#Astro...
    - mikeash 11y ago
      Amazingly, it worked during the day (on the ground) too!
  - mxfh 11y ago
    The patent mentioned only covers projecting a light pattern to the ceiling of a room for indoor-navigation of household robots.
    - dagw 11y ago
      My mistake. I guess I should know better than to only read the title of a patent.
- mninm 11y ago
  Trident missiles (a type of ICBM currently being carried aboard US submarines) do just that. Once launched a Trident, using a camera, gets a fix on a single specific star. It then uses the data on that star's position to correct for any errors in its internal guidance system. See: https://en.wikipedia.org/wiki/Trident_(missile) https://en.wikipedia.org/wiki/Trident_(missile)
dctoedt 11y ago
I sort-of learned celestial navigation during Navy ROTC training 40 years ago. I remember the Nautical Almanac being something of a pain to work with. It would have been so nice to have the modern-day mobile-device apps that will take the sextant data and do the table-lookup number crunching.
- tribe 11y ago
  Even with a mobile app, it may still be worth knowing how to navigate the old fashioned way. I would imagine that books / hand calculations are more resistant to power failure than apps and GPS are.
  - chiph 11y ago
    Or in the case of military applications, proof against EMP.
    - Nrsolis 11y ago
      On my boat, we still did firing solutions for torpedoes using a slide ruler. The military is quick to embrace new technology but slow to completely rely on it to the exclusion of other methods. The great fear is that technology will let you down at a critical moment via failure or damage. That's why they teach the old methods alongside the new ones.
      - chiph 11y ago
        Agree. When I was in the USAF, we had micro-processor controlled communication systems, but also still had the 1950's Teletypes as backups. Running a war at 75 baud... One time we bolted some backpack straps to one, painted it camo, and called it our Tactical Teletype. The joke was that it was 350 pounds of steel parts and electric motor...
        knodi123 11y ago
        I wonder if modern fighter pilots still need to learn old NDB and ADF radio beacon navigation? In a modern jet, I assume that if your computer-aided nav systems are non-functional, the plane is probably non-functional as well?
maze-le 11y ago
It is always good to have a backup system, in case the primary system (GPS) fails. Celestial navigation has a proven track-record for centuries. I wonder more why it was dropped in the first place...
- moron4hire 11y ago
  US Military Doctrine is fundamentally tied to the Myth of Progress (https://en.wikipedia.org/wiki/Idea_of_Progress#Myth_of_Progress https://en.wikipedia.org/wiki/Idea_of_Progress#Myth_of_Progr...).
  - crpatino 11y ago
    It is surreal to see this mentioned here. HN mindset is progressive, after all. But to qualify this comment, I'd say that what is specifically tied to the Myth of Progress in US Military Doctrine is the bias against thinking that an opponent relying on low(er) tech can negate/overcome this disadvantage through the use of superior tactics. For reference see: https://en.wikipedia.org/wiki/Millennium_Challenge_2002 https://en.wikipedia.org/wiki/Millennium_Challenge_2002
    - toomuchtodo 11y ago
      This reminded me of the film Down Periscope.
- ckozlowski 11y ago
  If the only concern was that your GPS receiver could fail, then you could rely on your backup system. Either a second receiver, or some other system. (TACAN, INS, etc.) Their concern seems to be, "What if none of the electronic systems can be trusted?" That wasn't as much a concern when the sextant courses were dropped, but they are now, which is why it seems they're reinstating them. Curiously, INS (inertial navigation system), which uses gyroscopes, is often turned to as a backup for when GPS can't be used, or is otherwise unavailable. (Many guided systems now can use INS as a backup if the GPS signal is jammed.) Most ships have this as well. Presumably this would be an adequate fallback. That being said, if my ship were dead in the water with no electrical power, this seems like a no-brainer.
DrJokepu 11y ago
Do commissioned officers actually do any navigation at all? I understood that this is mostly done by enlisted quartermasters (QM) an navigation electronics technicians (ET).
- Nrsolis 11y ago
  You bet they do. Commissioned officers are responsible for the boat and the crew. That doesn't mean that they do all the work, but they are responsible for making sure it's done correctly and getting it done correctly if the crew can't. They are also responsible for training the crew to the highest standards. Source: spent two years at the Naval Academy and one tour on a nuclear submarine during the summer.
moosetafa 11y ago
Now, if the Navy wanted their sailors to be truly hardcore navigators and be totally immune from cyber hacking, they'd have them use an abacus for calculations rather than a calculator or computer.
- outworlder 11y ago
  If an enemy has managed to fry or otherwise interfere with the electronics of calculators, you expect that the balls of mostly water will have other, more serious, issues.
- tonyarkles 11y ago
  Slide rule... we're not cavemen!
csense 11y ago
Isn't the GPS signal fairly low-power, and thus, trivial for an enemy to jam? Or would they have to get their jammer close enough to be in range of the ship's guns (and presumably its loud radio broadcasts would give away its position)?
- VLM 11y ago
  There's no reason a battery powered jammer won't fit in a bouy or "mine" or drone. If you're already declared an area a "no fly zone" or "no float zone" then jamming civilians is not going to be a serious concern. We're coming to the end of a golden era where RF electronic reasons used to mean significant jamming was somewhat unrealistic at an analog electronics level. In the "next big war" jamming is going to be cheap and ubiquitous on the battlefield (or for that matter, in terror attacks or whatever). There is an interesting economic warfare aspect where a jammer drone is inherently always going to be cheaper than the antiaircraft missile or antiaircraft drone that shoots it down due to certain precision flying and targeting requirements. A jammer has to keep the right side up and not hit anything, and anti-jammer has a much more complicated task of finding, reaching, and destroying a jammer. So it being cheaper to jam than to unjam means only the wealthiest aggressors with good logistics support will be able to decide when GPS will be usable on a battlefield. Also unjaming has certain risks... sure go ahead shoot down that jammer drone, the site that launches a missile or even a drone will get plastered about one minute later by what amounts to counterbattery artillery fire. Now you have GPS data but no anti-aircraft cover... hmm, probably not a good trade. This is before meta level games are played where you want to lure someone into an ambush by jamming the heck out of everything but one heavily armed and prepared "empty" mountain pass. In the future I think you can pretty much count on GPS not being available or at least not being reliable on the battlefield, and when the enemy does let you use GPS they're probably messing with you. The concept of drones being cheaper than what it takes to shoot them down has a meta problem first discussed in anti-star-wars technology in the 80s where MIRV ICBMs had decoys... You can expect X drones of which only Y contain expensive jammer hardware, making the cost ratio of anti-jammer drones even worse compared to jammer and decoy drones.
  - DannoHung 11y ago
VLM 11y ago
One interesting side effect of learning celestial nav is you can't avoid learning some astronomy and keeping up to date on the night sky. Another side effect is its a filter on people who can't handle math or can't handle complicated written procedures. Its unclear how important that is, but it is clear its a very good filter if you value those skills for other reasons. With respect to situational awareness, its very easy to own a GPS while confusing that attribute of ownership with understanding where you are, but its very hard to mentally do celestial nav without understanding where you are, what are the present sea and weather conditions. Also there is a difference between merely owning a (possibly GPS accurate) clock or chronometer and understanding what time it is. "I own things that could provide accurate 4 dimensional situation, were I to actually understand the outputs" is a lot different from "I can perform extensive labor and calculations with the result of being deeply aware of my 4 dimensional situation"
- dfc 11y ago
  > its a filter on people who can't handle math or can't handle complicated written procedures. Do you think that the USNA admissions process and or the Academy's graduation requirements do not provide an equivalent filter?
  - VLM 11y ago
    Conversely if the upstream filters are working, then its not going to hurt anything to implement, is it? I agree its a much more useful discriminator for civilians than naval officers or professional sailors.
joshuaheard 11y ago
I'm surprised they gave it up. It is still best practice in yachting to have at least one crew member on an ocean crossing be able to do celestial navigation. You can't count on electricity, and thus GPS, so you have to return to the basics as a backup.
- Perdition 11y ago
  On a modern naval vessel if you lose all the electronics the ship is going to be drifting anyway. Still it seems smart to keep the skill around as the GPS system can be locally jammed and in WWIII could be completely knocked out.
  - zappo2938 11y ago
    Maybe not. Marine diesel engines can run without the computers attached using mechanical throttles. There has been instances where the yacht's wheelhouse is flooded with water and all the navigation computers and electronic controls are lost. The captain and mate stationed in the engine room coordinate by controlling the manual throttles on each engine. Move one throttle more to turn.
    - scrumper 11y ago
      Depends on the ship of course, but this wouldn't have worked on at least one of the naval vessels I've visited. Common on newer ships are electric drives, where diesel or gas turbine engines are connected to generators instead of prop shafts.
SCAQTony 11y ago
I am presuming an even darker scenario. GPS signals would not be jammed by the enemy but rather satellites would be obliterated wholesale as a result of a limited nuclear exchange. Thus sailing the old fashion way: Sextant, watch, and maps are the only way home.
- deleted 11y ago
  [deleted]
- txru 11y ago
  EMP/Infrastructure destruction wholesale is a pretty safe bet for any first strike.
- JulianMorrison 11y ago
  Or Kessler Syndrome. Deliberate or otherwise.
  - deleted 11y ago
    [deleted]
  - simonh 11y ago
    Kessler Syndrome is mainly a Low Earth orbit issue. GPS sats are at 20,000 km altitude so aren't particularly vulnerable to it. They're probably far enough away to not be vulnerable to EMP either, unless someone were to lob a nuke out pretty far.
hackuser 11y ago
My impression, based on very limited knowledge, has been that inertial navigation was the backup to or even replacement for GPS. Does anyone know more about it?
dpeck 11y ago
For anyone interested, I taught myself the basics of celestial navigation a few years back after being interested in it for years. Something just feels right and maybe a bit primal about knowing where you are relative to the heavens. I used the book http://smile.amazon.com/Celestial-Navigation-GPS-John-Karl/dp/0939837757 http://smile.amazon.com/Celestial-Navigation-GPS-John-Karl/d... and really enjoyed it. Fun to do with kids too. Edit: And the http://smile.amazon.com/Davis-Mark-3-Marine-Sextant/dp/B0014476FI/ref=sr_1_1?ie=UTF8&qid=1444844189&sr=8-1&keywords=davis+mark+3+sextant http://smile.amazon.com/Davis-Mark-3-Marine-Sextant/dp/B0014... makes a fine sextant to start with.
- wyclif 11y ago
  I'd be interested in more book suggestions.
  - 5555624 11y ago
    "Dutton's Navigation & Piloting, 13th Edition" http://www.amazon.com/Duttons-Navigation-Piloting-Elbert-Maloney/dp/B000TN97X4/ref=sr_1_3?s=books&ie=UTF8&qid=1444849795&sr=1-3&keywords=dutton%27s+navigation+and+piloting http://www.amazon.com/Duttons-Navigation-Piloting-Elbert-Mal... Although the most recent edition is the 15th (2003), I learned with the 13th, so I know its useful. The 13th was also pre-GPS and spent only 30 or so pages on Loran, so it's mostly celestial and coastal, in addition to piloting.
  - Luc 11y ago
    John Karl's book is very good. My favourite is 'Self-contained Celestial Navigation with HO 208' by John Letcher. It's out of print but used copies show up on abebooks for a reasonable price at times. It's often recommended. I also like 'The Sextant Handbook' by Bruce Bauer. Also out of print. A very nice modern coffee-table book about the history of celestial navigation is 'Finding Longitude' by Richard Dunn e.a. : http://www.amazon.com/dp/B00HPMW95A http://www.amazon.com/dp/B00HPMW95A Finally, you could subscribe to NavList at fer3.com. There's enough in the archives to fill several books and the people there really know their stuff (well, not me so much, but others do!).
  - 11y ago
w8rbt 11y ago
This is also why non-network based communication backups are important. HF radios, NVIS and Morse Code are very efficient and effective when network packets are not flowing.

99 points by curtis 11y ago

I wonder if they also asked trained officers to do regular practise? The theory behind celestial navigation is fairly trivial (I've almost forgotten it all but give me an alamnac and an hour and I'm confident I'd work it all out). The successful use of a sextant for a decent fix however requires training, practise and regular use to keep your skills sharp.

gchadwick 11y ago
> But it's only three hours of celestial navigation — so students won't be skilled with sextants. Looks like they won't even get a sextant out of its box
Tepix 11y ago
Moxie Marlinspike's documentary "Hold fast" (2010) [1] inspired me to learn how to use a sextant. Most of the sextants you can get on eBay these days are just for decoration, however. [1] "Hold Fast: Stories of maniac sailors, anarchist castaways, and the voyage of the S/V Pestilence..." https://vimeo.com/15351476 https://vimeo.com/15351476
- Luc 11y ago
  > Most of the sextants you can get on eBay these days are just for decoration, however. Ugh, these things are a plague. There's a factory in India pumping out most of these. They do a whole bunch of variations, boxes, antiquing, etc. Some sellers on eBay list them as genuine antique instruments, which is straight up deception. The replicas of box sextants (small pocket instruments in the shape of a round box) are especially hard to spot if the seller is dishonest.
sizzzzlerz 11y ago
Its also one thing, taking a sight on land but a whole other thing doing it on the ocean when the ship is rockin' and rollin'. That takes practice, too.

yread 11y ago

RYA Yachtmaster course requires celestial navigation and some schools even require candidates to perform the navigation on the qualifying passage (couple hundred nm) without GPS.

gchadwick 11y ago
It's the Yachtmaster Ocean, and as far as I know you're allowed to use GPS on your qualifying passage you simply have to take some sights whilst on passage to present to the examiner. I think they also allow for cloudy weather preventing any sights from being taken and allow you to present some from another trip. There's some controversy there too as to whether it should be left in the syllabus. Personally I think it's a nice thing to do, there's something very pleasing about producing a fix especially when you do fun things like producing a running fix from sun and moon sights.
- Robadob 11y ago
  > I think they also allow for cloudy weather preventing any sights from being taken Is there not a modern equivalent of the medieval 'sun stone'? https://en.wikipedia.org/wiki/Sunstone_(medieval) https://en.wikipedia.org/wiki/Sunstone_(medieval)
  - sethrin 11y ago
    Knowing the direction of the sun to within a few degrees is unlikely to help much. For one thing, you have no other "fix", and for another, an error factor of a few degrees probably represents an error of a few hundred (nautical) miles. You should probably read a bit more about celestial navigation to understand the problem.

xg15 11y ago

I wonder if, with the use of image analysis, it would be possible to create a "robo-sextant" - i.e. a system which scans the sky in certain intervals, locates the waterline, sun or other celestial bodies and performs the necessary calculations. Such a system could be used to e.g. detect GPS manipulation quickly

dagw 11y ago
It's an idea that has been around for awhile: http://www.ri.cmu.edu/pub_files/pub2/cozman_fabio_1995_1/cozman_fabio_1995_1.pdf http://www.ri.cmu.edu/pub_files/pub2/cozman_fabio_1995_1/coz... is just one of dozens of papers covering the idea. There even appears to be a patent on the idea: https://www.google.com/patents/US7706917 https://www.google.com/patents/US7706917
- Ao7bei3s 11y ago
  It has actually been done: the SR-71 Blackbird had one. https://en.wikipedia.org/wiki/Lockheed_SR-71_Blackbird#Astro-Inertial_Navigation_System https://en.wikipedia.org/wiki/Lockheed_SR-71_Blackbird#Astro...
  - mikeash 11y ago
    Amazingly, it worked during the day (on the ground) too!
- mxfh 11y ago
  The patent mentioned only covers projecting a light pattern to the ceiling of a room for indoor-navigation of household robots.
  - dagw 11y ago
    My mistake. I guess I should know better than to only read the title of a patent.
mninm 11y ago
Trident missiles (a type of ICBM currently being carried aboard US submarines) do just that. Once launched a Trident, using a camera, gets a fix on a single specific star. It then uses the data on that star's position to correct for any errors in its internal guidance system. See: https://en.wikipedia.org/wiki/Trident_(missile) https://en.wikipedia.org/wiki/Trident_(missile)

dctoedt 11y ago

I sort-of learned celestial navigation during Navy ROTC training 40 years ago. I remember the Nautical Almanac being something of a pain to work with. It would have been so nice to have the modern-day mobile-device apps that will take the sextant data and do the table-lookup number crunching.

tribe 11y ago
Even with a mobile app, it may still be worth knowing how to navigate the old fashioned way. I would imagine that books / hand calculations are more resistant to power failure than apps and GPS are.
- chiph 11y ago
  Or in the case of military applications, proof against EMP.
  - Nrsolis 11y ago
    On my boat, we still did firing solutions for torpedoes using a slide ruler. The military is quick to embrace new technology but slow to completely rely on it to the exclusion of other methods. The great fear is that technology will let you down at a critical moment via failure or damage. That's why they teach the old methods alongside the new ones.
    - chiph 11y ago
      Agree. When I was in the USAF, we had micro-processor controlled communication systems, but also still had the 1950's Teletypes as backups. Running a war at 75 baud... One time we bolted some backpack straps to one, painted it camo, and called it our Tactical Teletype. The joke was that it was 350 pounds of steel parts and electric motor...
      - knodi123 11y ago
        I wonder if modern fighter pilots still need to learn old NDB and ADF radio beacon navigation? In a modern jet, I assume that if your computer-aided nav systems are non-functional, the plane is probably non-functional as well?

maze-le 11y ago

It is always good to have a backup system, in case the primary system (GPS) fails. Celestial navigation has a proven track-record for centuries. I wonder more why it was dropped in the first place...

moron4hire 11y ago
US Military Doctrine is fundamentally tied to the Myth of Progress (https://en.wikipedia.org/wiki/Idea_of_Progress#Myth_of_Progress https://en.wikipedia.org/wiki/Idea_of_Progress#Myth_of_Progr...).
- crpatino 11y ago
  It is surreal to see this mentioned here. HN mindset is progressive, after all. But to qualify this comment, I'd say that what is specifically tied to the Myth of Progress in US Military Doctrine is the bias against thinking that an opponent relying on low(er) tech can negate/overcome this disadvantage through the use of superior tactics. For reference see: https://en.wikipedia.org/wiki/Millennium_Challenge_2002 https://en.wikipedia.org/wiki/Millennium_Challenge_2002
  - toomuchtodo 11y ago
    This reminded me of the film Down Periscope.
ckozlowski 11y ago
If the only concern was that your GPS receiver could fail, then you could rely on your backup system. Either a second receiver, or some other system. (TACAN, INS, etc.) Their concern seems to be, "What if none of the electronic systems can be trusted?" That wasn't as much a concern when the sextant courses were dropped, but they are now, which is why it seems they're reinstating them. Curiously, INS (inertial navigation system), which uses gyroscopes, is often turned to as a backup for when GPS can't be used, or is otherwise unavailable. (Many guided systems now can use INS as a backup if the GPS signal is jammed.) Most ships have this as well. Presumably this would be an adequate fallback. That being said, if my ship were dead in the water with no electrical power, this seems like a no-brainer.

DrJokepu 11y ago

Do commissioned officers actually do any navigation at all? I understood that this is mostly done by enlisted quartermasters (QM) an navigation electronics technicians (ET).

Nrsolis 11y ago
You bet they do. Commissioned officers are responsible for the boat and the crew. That doesn't mean that they do all the work, but they are responsible for making sure it's done correctly and getting it done correctly if the crew can't. They are also responsible for training the crew to the highest standards. Source: spent two years at the Naval Academy and one tour on a nuclear submarine during the summer.

moosetafa 11y ago

Now, if the Navy wanted their sailors to be truly hardcore navigators and be totally immune from cyber hacking, they'd have them use an abacus for calculations rather than a calculator or computer.

outworlder 11y ago
If an enemy has managed to fry or otherwise interfere with the electronics of calculators, you expect that the balls of mostly water will have other, more serious, issues.
tonyarkles 11y ago
Slide rule... we're not cavemen!

csense 11y ago

Isn't the GPS signal fairly low-power, and thus, trivial for an enemy to jam? Or would they have to get their jammer close enough to be in range of the ship's guns (and presumably its loud radio broadcasts would give away its position)?

VLM 11y ago
There's no reason a battery powered jammer won't fit in a bouy or "mine" or drone. If you're already declared an area a "no fly zone" or "no float zone" then jamming civilians is not going to be a serious concern. We're coming to the end of a golden era where RF electronic reasons used to mean significant jamming was somewhat unrealistic at an analog electronics level. In the "next big war" jamming is going to be cheap and ubiquitous on the battlefield (or for that matter, in terror attacks or whatever). There is an interesting economic warfare aspect where a jammer drone is inherently always going to be cheaper than the antiaircraft missile or antiaircraft drone that shoots it down due to certain precision flying and targeting requirements. A jammer has to keep the right side up and not hit anything, and anti-jammer has a much more complicated task of finding, reaching, and destroying a jammer. So it being cheaper to jam than to unjam means only the wealthiest aggressors with good logistics support will be able to decide when GPS will be usable on a battlefield. Also unjaming has certain risks... sure go ahead shoot down that jammer drone, the site that launches a missile or even a drone will get plastered about one minute later by what amounts to counterbattery artillery fire. Now you have GPS data but no anti-aircraft cover... hmm, probably not a good trade. This is before meta level games are played where you want to lure someone into an ambush by jamming the heck out of everything but one heavily armed and prepared "empty" mountain pass. In the future I think you can pretty much count on GPS not being available or at least not being reliable on the battlefield, and when the enemy does let you use GPS they're probably messing with you. The concept of drones being cheaper than what it takes to shoot them down has a meta problem first discussed in anti-star-wars technology in the 80s where MIRV ICBMs had decoys... You can expect X drones of which only Y contain expensive jammer hardware, making the cost ratio of anti-jammer drones even worse compared to jammer and decoy drones.
- DannoHung 11y ago

VLM 11y ago

One interesting side effect of learning celestial nav is you can't avoid learning some astronomy and keeping up to date on the night sky. Another side effect is its a filter on people who can't handle math or can't handle complicated written procedures. Its unclear how important that is, but it is clear its a very good filter if you value those skills for other reasons. With respect to situational awareness, its very easy to own a GPS while confusing that attribute of ownership with understanding where you are, but its very hard to mentally do celestial nav without understanding where you are, what are the present sea and weather conditions. Also there is a difference between merely owning a (possibly GPS accurate) clock or chronometer and understanding what time it is. "I own things that could provide accurate 4 dimensional situation, were I to actually understand the outputs" is a lot different from "I can perform extensive labor and calculations with the result of being deeply aware of my 4 dimensional situation"

dfc 11y ago
> its a filter on people who can't handle math or can't handle complicated written procedures. Do you think that the USNA admissions process and or the Academy's graduation requirements do not provide an equivalent filter?
- VLM 11y ago
  Conversely if the upstream filters are working, then its not going to hurt anything to implement, is it? I agree its a much more useful discriminator for civilians than naval officers or professional sailors.

joshuaheard 11y ago

I'm surprised they gave it up. It is still best practice in yachting to have at least one crew member on an ocean crossing be able to do celestial navigation. You can't count on electricity, and thus GPS, so you have to return to the basics as a backup.

Perdition 11y ago
On a modern naval vessel if you lose all the electronics the ship is going to be drifting anyway. Still it seems smart to keep the skill around as the GPS system can be locally jammed and in WWIII could be completely knocked out.
- zappo2938 11y ago
  Maybe not. Marine diesel engines can run without the computers attached using mechanical throttles. There has been instances where the yacht's wheelhouse is flooded with water and all the navigation computers and electronic controls are lost. The captain and mate stationed in the engine room coordinate by controlling the manual throttles on each engine. Move one throttle more to turn.
  - scrumper 11y ago
    Depends on the ship of course, but this wouldn't have worked on at least one of the naval vessels I've visited. Common on newer ships are electric drives, where diesel or gas turbine engines are connected to generators instead of prop shafts.

SCAQTony 11y ago

I am presuming an even darker scenario. GPS signals would not be jammed by the enemy but rather satellites would be obliterated wholesale as a result of a limited nuclear exchange. Thus sailing the old fashion way: Sextant, watch, and maps are the only way home.

deleted 11y ago
[deleted]
txru 11y ago
EMP/Infrastructure destruction wholesale is a pretty safe bet for any first strike.
JulianMorrison 11y ago
Or Kessler Syndrome. Deliberate or otherwise.
- deleted 11y ago
  [deleted]
- simonh 11y ago
  Kessler Syndrome is mainly a Low Earth orbit issue. GPS sats are at 20,000 km altitude so aren't particularly vulnerable to it. They're probably far enough away to not be vulnerable to EMP either, unless someone were to lob a nuke out pretty far.

hackuser 11y ago

My impression, based on very limited knowledge, has been that inertial navigation was the backup to or even replacement for GPS. Does anyone know more about it?

dpeck 11y ago

For anyone interested, I taught myself the basics of celestial navigation a few years back after being interested in it for years. Something just feels right and maybe a bit primal about knowing where you are relative to the heavens. I used the book http://smile.amazon.com/Celestial-Navigation-GPS-John-Karl/dp/0939837757 http://smile.amazon.com/Celestial-Navigation-GPS-John-Karl/d... and really enjoyed it. Fun to do with kids too. Edit: And the http://smile.amazon.com/Davis-Mark-3-Marine-Sextant/dp/B0014476FI/ref=sr_1_1?ie=UTF8&qid=1444844189&sr=8-1&keywords=davis+mark+3+sextant http://smile.amazon.com/Davis-Mark-3-Marine-Sextant/dp/B0014... makes a fine sextant to start with.

wyclif 11y ago
I'd be interested in more book suggestions.
- 5555624 11y ago
  "Dutton's Navigation & Piloting, 13th Edition" http://www.amazon.com/Duttons-Navigation-Piloting-Elbert-Maloney/dp/B000TN97X4/ref=sr_1_3?s=books&ie=UTF8&qid=1444849795&sr=1-3&keywords=dutton%27s+navigation+and+piloting http://www.amazon.com/Duttons-Navigation-Piloting-Elbert-Mal... Although the most recent edition is the 15th (2003), I learned with the 13th, so I know its useful. The 13th was also pre-GPS and spent only 30 or so pages on Loran, so it's mostly celestial and coastal, in addition to piloting.
- Luc 11y ago
  John Karl's book is very good. My favourite is 'Self-contained Celestial Navigation with HO 208' by John Letcher. It's out of print but used copies show up on abebooks for a reasonable price at times. It's often recommended. I also like 'The Sextant Handbook' by Bruce Bauer. Also out of print. A very nice modern coffee-table book about the history of celestial navigation is 'Finding Longitude' by Richard Dunn e.a. : http://www.amazon.com/dp/B00HPMW95A http://www.amazon.com/dp/B00HPMW95A Finally, you could subscribe to NavList at fer3.com. There's enough in the archives to fill several books and the people there really know their stuff (well, not me so much, but others do!).
- 11y ago

w8rbt 11y ago

This is also why non-network based communication backups are important. HF radios, NVIS and Morse Code are very efficient and effective when network packets are not flowing.