NavList:

Robert Eno, you wrote:
"The fact that you even came up with this notion makes me wonder if you are a diabolical super-villain in the making."

In the making?? :)

You wrote:
"I have to agree with Brad. I buy my NA from the US Gov't publishing office and it is therefore hard to break that chain of custody."

As I mentioned to Brad, I think the easiest way to handle this would be to send out a package containing the "improved" almanac with instructions for marking the real one unfit for navigation (that process of "defiling" the supposedly erroneous almanac would give the mark a positive feeling towards the fake almanac).

You added:
"That being said, I think spoofing the NA would have to be subtle but you would also need your own publishing and printing equipment to reproduce an NA that would be physically identical to the real thing."

I agree that this is the expensive step. Twenty years ago this would have been nearly impossible except perhaps for some other government's printing offices. But today I think you could order a hundred copies that would be materially indistinguishable from the real thing for a few thousand dollars. Expensive, but not prohibitive.

You suggested:
"How would I do it? Just off the top of my head, I would reverse the declination of all of the celestial bodies and for good measure, add or subtract about 2 - 3 degrees to/from each. If I wanted to go the whole way, I would also alter the GHA by several degrees."

Wait, reverse the declination? You mean north for south?? I think that might raise some alarms! As Antoine also noted, shifting the GHA (by an increasing amount as the voyage progresses) is clearly feasible. And almost completely undetectable. It's equivalent, of course, to offsetting the GMT displayed by all timepieces onboard.

You wrote:
"As Brad has correctly pointed out, these changes would have to be done incrementally; in such a way that the ephemeris data for the start of the trip is correct and subsequent data would be degraded as the days wear on."

Yes, that's why I threw in the bit about knowing the approximate date of departure. Clearly the first celestial fix, perhaps even taken while within sight of Hawaii, must be nearly correct. This, by the way, is quite similar to the description of the GPS spoofing process that's been in the press. They take over the signals and start out by showing the target's spoofed position to be exactly where they are. Then the solution is gradually drifted away. We could do the same in celestial spoofing.

Thinking like a diabolical genius now, you wrote:
"Now you have to have a team of black-suited Ninjas to get into each and every yacht to switch out the NAs. And to do that, I would set up a large celebratory banquet for the racers in order to get them all away from their yachts so that my Ninja team can do their dirty deed."

Of course! We're all good yachting pals. We need a party, with a lot of alcohol. And with enough wine flowing, you wouldn't even need those ninjas --the same people paid to pour the wine might be paid to swap the almanacs (if we have not used my mailing trick, as above).

Continuing in diabolical mode, you wrote:
"You mentioned that our perspective sailors only have a working knowledge of nautical astronomy so I would -- as the maniacal villain -- hope that they would not detect the subtle changes and presto: they are sailing towards oblivion."

I agree, of course. So the next question, if you want to continue with this game, is to ask just how far we could send them off course before the clues would become obvious.

"A very interesting concept Frank, or should I refer to you as "Snidely Whiplash"? Bwaahaahaa!"

Shhh! The NSA is listening. :)

-FER

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