Naval Academy reinstates celestial navigation(navytimes.com) |
Naval Academy reinstates celestial navigation(navytimes.com) |
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.
Only on Earth we used it as one of the navigation systems to get astronauts on the moon.
The Academy doesn't train the "sailors", though, just an elite corps of officers, and you don't need to have everyone on board making his own book, just have a few specially trained people (on land, presumably) who could if they needed to. They Academy makes sure many such people exist.
You'd harden the system against EMP which is probably a standard requirement of military electronics anyway (I'd hope...)
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.
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-7...
http://www.amazon.com/Ghost-Fleet-Novel-Next-World/dp/054414...
You'd think the proof reader would at least catch an issue in the very first sentence.
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.
Celestial navigation requires (the computational equivalent of) a graphing calculator.
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.
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...