NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Brad Morris
Date: 2013 Aug 2, 21:48 -0400
1) I buy my NA directly from the government publishing office. Others may do so too. Awfully hard to break that chain of custody at the Post Office to my door.
2) Suppose you did have a bogus Nautical Almanac. You would get 'unusual' results, which may cause you to compare your NA with others, leading to discovery.
3) In order for the 'dastardly' plan to work, you would have to cause significant change such that landfall sight would be eliminated. That's a big change, requiring either a single jump in the data (which would be self evident when detected) or an entire offset in the bogus NA (which would be self evident at the start of the race, because the know point of departure would not agree with the first celestial observation.
4) Of course, you say, it could be right at the start of the trip and meander away from the truth incrementally until at the end it was significantly wrong. While feasible, its just not practical for pirating or for military purposes, ala GPS spoofing.
Sadly, I just don't think that's a practical way to spoof celestial.
How about spoofing the time signal? Just provide a stronger radio time check than the real one at the appropriate frequency (to swamp the true signal) and shift the time. That will do it.
Brad
We joked a bit a few days ago about spoofing celestial navigation. But now I would like to propose a (slightly) more feasible scenario...
Let us suppose that some wealthy yachtsmen are prepared to race by sailing vessel from Hawaii to Tahiti using only traditional twentieth century celestial navigation and necessarily also traditional dead reckoning. The teams will race with absolutely no access to GPS and in complete radio silence except in the event of an emergency. They can, of course, see all the traditional signs of the ocean. Let's assume we know the date of departure. Make it tomorrow, August 3, 2013 for a specific. And let's assume that they take their departure (last clear sight of land at a known distance) from the southernmost tip of the Big Island. From there they will sail to Tahiti using only DR and celestial. The race is fair, but you are a diabolical super-villain wannabe --a teenage "hacker"-- with a need to embarass the wealthy captains of the yachts. So by a little trickery, you will arrange to "spoof" the celestial navigation and send them to Easter Island instead of Tahiti.
Both GPS and celestial navigation depend on data from "on high" that is largely out of the navigator's control. Data which the navigator must accept, more or less as a matter of faith. In the case of GPS, that is obvious: it is the signals themselves. For celestial navigation, that data which the navigator must trust as a matter of faith is, of course, the Nautical Almanac (and its equivalents). And that is our target. SPOOF the Nautical Almanac!
Could you do it? How would you modify the data in a counterfeit almanac to send these racing yachts to the wrong corner of the vast Pacific Ocean? How well would this subterfuge work? How might they detect that something is wrong? To be fair to the spirit of the challenge, you can assume that these navigators are not rocket scientists. You can assume that they are skilled and confident and equipped with excellent sextants and chronometers, but they have only a "working knowledge" of nautical astronomy.
I think this trick could be pulled off at a cost of less than five thousand dollars. So why didn't anyone try this in the long history of celestial navigation?
-FER
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