The name is perfect. "Etak" refers to a system of navigation used by Micronesian and Polynesian seafarers to navigate from island to island in the vast Pacific Ocean. Much like this device, it operates by "augmented dead reckoning" (as it says in TFA).
The etak system of navigation involves navigating by stars and ocean swells to get the heading, but a key issue when navigating by dead reckoning over long distances is that if you're a fraction of a degree off you may miss your destination and never know it, so it's also vitally important to know how far you've gone. This is hard when there are no landmarks. The navigators estimated their distance by using intermediary islands off to the side, which they viewed as coming towards them (from their point of view, the navigator stays motionless on the open ocean while the world moves towards them) and past them. These reference islands were called etaks.
However, confusingly, the etaks were generally not visible, being beyond the horizon, and sometimes did not even exist. The navigators would have named etaks that they pictured being just over the horizon, whether they were there or not, and would track their procession past their boat. When the set number of etaks had passed, they would know they were in the vicinity of the destination island. If they were not at the right time of day for birds to be out, they would then hang out in the area waiting to spot the birds leaving or returning at dawn or dusk.
So the system involves dead reckoning plus a system of turning the navigators' own well-developed intuition of how far they had travelled into a formalized system of generally-invisible islands that they used as a mental model to externalize this intuition.
(My knowledge of this is from Cognition in the wild, Hutchins, E., 1995.)
Edit: D'oh, I should have finished TFA. This is described at the end, although more roughly.
That sounds fascinating, but it's not really clear to me how imagining islands beyond the horizon can help with dead reckoning. Maybe there are changes in observable phenomena, such as ocean currents, that are associated with these unseen islands? It does sound like a very complex system based on the beginning of this article; I'm wondering if anyone here has read the books mentioned in it: https://www.jstor.org/stable/20705519
Yeah, this surprised me as well. I get how reading ocean swells, sea life, birds, ocean color (indicating depth and/or plant life below) could give a general sense of position. And I can see how stars, prevailing currents and maybe even estimates based on the relative movement of clouds (adjusted for ambient wind direction and weather conditions) could give a general sense of distance traveled. But on a completely cloudless day (or fully overcast night) gauging distance traveled seems like it could be catastrophically imprecise often enough to make for short navigation careers.
I'm not sure how the concept of tracking virtual islands over the horizon really helps. The only thing I can think of is maybe the idea of it encourages the navigator to stay focused on estimating the passage of proxy points on the far horizon based on whatever composite of wind, current and swell signs they are intuiting from. While still quite variable, I assume gauging distance estimates on the far horizon is better than the alternative of trying to estimate distance traveled from the immediate surroundings of the craft (which are only useful for estimating velocity).
You can practice navagating against physical islands over the horizon, and when you're good at that, you've mostly gotten good at dead reckoning against a real reference point; of course, with corrections from the islands influence. Having a community shared archipelego of virtual islands lets you focus your dead reckoning skills on a point while offering a vocabulary of distance and reducing travel times between waypoints.
Go 1000 miles in this direction seems a lot harder for me to follow over many days than go X miles to A, then Y miles to B, then Z miles to C. Even if A and B aren't real. If I treat them as very small islands that will be over the horizon, no big deal that they don't influence the environment, they're small; but I can't really use them to course correct, my reckoning needs to be good.
I've found a bit more information about the topic in a publicly available research article [1]:
"A depth of only 25 fathoms is quite enough to give some surface indications: coloration, wave phenomena, perhaps fauna. Is this the explanation of the ghost island? Some lost traveller, perhaps en route from Yap to Guam, seeing and remembering these phenomena, later reifying them as an inhabited land? Or is it possible that a real island once existed here, as the Carolinians say? [...] Any Carolinian navigator worthy of the name can give a whole set of radiating courses under all the navigation stars from every island of the Carolines, not just from Kaafiror. [... N]avigators do learn them, together with the courses from real islands, and they make no distinction among them. It is perhaps not altogether in the realm of fantasy to speculate that the curriculum of the schools of navigation was established in a time when Kaafifor was more than a discolored patch of water."
[1] https://micronesica.org/sites/default/files/the_ghost_island...
The explanation could be a combination of experience, details, survivor bias and true scottman.
That is with experience you can select something on the ocean far away that you can track (kelp, etc), with experience and focus to accurately track it and take into account its own movement. Then the method is obviously only promoted by those who successfully survived using it, as the potential nay-sayers who used it and failed are no longer there to give a counter-point. Finally, those who did not use it successfully are probably characterized as "not good navigators", in circular logic.
You know how if you turn the light on for a second you can then move through a dark room without touching anything?
The boundary between "imagining" and "visualizing" is somewhere between these two experiences but conceptually they are not that different.
I've read somewhere that part of the method they intuited their way was to read the waves. As faraway land masses can affect the shape of waves, supposedly these navigators could "see" beyond the horizon due to how the swell was behaving.
I can sort of see that in a mind's eye, with rings of waves spreading as they bounce off obstacles in water. But that's bird's view of a miniature -- and seeing that from the surface would be a very different story.
https://worldhistorycommons.org/marshall-islands-stick-chart
It’s amazing they can read such nuance.
Look at something long enough, and you begin to intuit the patterns instinctively.
I think more than viewing a ring of waves bounce of objects in the water, they observed waves diffracting around an island
This sounds very romantic, but they were mostly at drift. Most very using rafts without any form of propulsion. "Navigation" across wast distances was one way road with no return ticket. They had to do it for overpopulation, not for some explorative spirit.
I think there's a large Maori population in Aotearoa that would disagree with this. Heyerdahl's theory was discredited a while ago
Do you have a source for your claims?
Granted, overpopulation drove much, but if it was all one way drifting, then why would the Hawai'ians have a channel named "the way to Tahiti"?
see also https://en.wikipedia.org/wiki/Hōkūleʻa
Oh, I thought it was just the name "Kate" reversed.
Another book specifically about the Polynesian navigators is The Last Navigator. Having no experience navigating at sea, parts of it were a bit over my head, but it was a great read. It also goes into the culture of the people who are the subject of the book.
It only happened in the late middle ages, after possibly millenia of experience navigating easier waters. They simply didn't teach their methods to anyone
Thank you for the fascinating comment and book recommendation.
Felt the article was heavy on ad copy and graphics.