Examples of the reference charts Jay Utah mentioned in the above post.
Of course the data on those charts come from formulas. There is a formula for computing the sun's declination angle from the day of the year [1-365]. But the formula requires you to take the sine of an angle, which again typically would require another table in the 1880s. Sitting in a lifeboat you wouldn't be able to estimate the sine to the precision demanded by the position given in the problem, even if you recalled the formula.
Captain Bligh, for example, was set adrift with a copy of Hamilton's
The Practical Navigator, which contains the necessary formulas and trigonometry tables. His post-mutiny log describes his noon sightings and how he used these to navigate his open boat to safety.
@Vixen's thought experiment omits these necessary elements.
It never fails to amaze that some actual learning can arise from such gibberish. Putting the E in ISF as they say.
Learning about basic navigation might be fun, but it has almost nothing to do with the questions
@Vixen was asked. Asking her to go in baby steps keeps her from dumping a random assortment of facts on the table and forcing her critics to try to make something of it. When she does that, she gets to berate her critics for the straw-man attempts to pull something coherent out of her dog's breakfast, or mock them for their apparent lack of genius to match hers. But here she's using it as an excuse to pretend to be the teacher. She thinks she gets to single out one critic, pretend to teach him, and thereby continue to pretend she's the smartest one in the room.
As I mentioned, she's trying to justify her use of "geopositioned" in a context that doesn't fit the definition. While navigating on Earth's surface is an interesting historical and technical topic (and
does have to do with "geopositioning"), it has nothing to do with photographing surface features from lunar orbit or transmitting television signals back to Earth.
She's just doing her very best to remind us she's a numbers person...
Except the only numbers in
@Vixen's thought experiment are cherry-picked terrestrial coordinates for some point off the coast of Ireland, for which any AI can tell you the nearest land and the direction to sail. She can pose the question and judge someone's answer without having to compute the correct answer herself first, or explain how it would be done. By pretending to be the teacher she's shifting the burden of proof.
To be fair, she's asking a conceptual question. Exact quantities may not be important. But the concepts
are important, and it's the concepts that she got wrong. She describes the navigation solution as having taken only fifteen minutes or so and to have taken place at some arbitrary time of day. She relates that the latitude solution was obtained using "only" a mystery instrument, then subsequently longitude using a timekeeping device, then she asks her chosen "student" to name the mystery device.
That sort of guessing game only works when the problem is otherwise fully specified. Purporting that you can do something with "only" certain equipment—ignoring other essentials—and asking students to guess at what that equipment could be is a fatally flawed question.
You take latitude sightings of the sun at local noon, as Bligh reports. This is the only way you can do it using
only a sextant, which was Vixen's problem statement. Unless the fifteen minutes specified in the problem included local noon, what she's claiming is impossible. There is a technique involving hour angles that you can use any time the sun can be sighted, but you need to know your reference time and longitude first. And as usual, it requires lookups in tables that the people in her problem don't have. In other words, not the given problem.
It's important for a teacher to teach from a position of deep conceptual understanding, not just of frantic Googling and AI prompting. It's also important for a "numbers person" to understand the proper relationships of the concepts represented by the numbers. Ignoring the need for lookup tables or other information not present in the problem does not make it a problem you can ask meaningful conceptional questions about.
I suspect
@Vixen will just forge ahead and gloss over the fact that she got the answer wrong.
). I'm not so sure that people who weren't involved with railroad operations would be aware of the difference between Railroad Time and local time, however. I have seen double clocks that were designed to show both times, though.
