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  • Love this. I often think of these applications when I see it in building windows where the screen and it's own reflection. I am tinkering virtually:

    https://www.ouruboroi.com/moire

    https://www.ouruboroi.com/moire2

    https://www.ouruboroi.com/moire3

    by cwmoore
  • If you tune two strings together, listening for beats, you are also guided by a moiré pattern. The whistle you hear when tuning an old AM radio is also moiré beats caused by the overlap of the local oscillator frequency and the incoming carrier.

    Another example of moiré for accurate indication: optical flats:

    https://en.wikipedia.org/wiki/Optical_flat

    This application shows how an optical flat resting on a gauge block indicates a tilt: showing that the adjacent object being tested is taller or shorter than the block by a minute amount. https://commons.wikimedia.org/wiki/File:Optical_flats_in_use...

    Interference patterns are basically moiré. Anything using interference for fine calibration is using moiré.

    by kazinator
  • The three-lamp triangle system is clever and reminds me of the Eye Reference Indicator in an aircraft cockpit. You adjust your seat so that the three balls are aligned in a specified way. [1]

    This is important in providing the correct visual reference out the window, as that in turn affects the pilot's perspective of other external cues.

    [1] https://safetyfirst.airbus.com/are-you-properly-seated/

    by bonzog
  • This reminds me of pre-GPS systems like LORAN [0], where it also involves ship navigation by demarcating everything into patterned regions.

    [0] https://en.wikipedia.org/wiki/LORAN

    by Terr_
  • A relatively simple system of lights is used at Portsmouth Harbour to help the aircraft carriers navigate the narrow channel in and out of port.

    This looks to be similar to the 3-light system that the author talks about.

    https://insidedio.blog.gov.uk/2016/08/22/safe-approach-to-po...

        To provide navigational certainty the vessel’s navigator visually aligns one set of three up with the other (i.e. they act as a pair) and because each of the three lights is a different colour the navigator can be certain he’s lining up the correct lights.
    by tomalpha
  • > "it's difficult to research something if you don't know the name of it"

    > - Tom Scott, 8 years ago

    Ah, research in the pre-LLM era was quite different. You actually had to know which questions to ask.

    Going one level down further, it's really hard to imagine what it was like doing research into something you have zero clue about in the pre-Google era. I guess you just asked a librarian and hoped they'd point you roughly towards the right section and then just started to read random books?

    by moffkalast
  • It's really neat that the author took the time to fabricate their own light.

    I've been looking for something similar in concept for when I back into my garage from a side street with basically no driveway. It's a very narrow single-car garage. I can consistently back in well enough for myself, but if I'm not dead-on and I have passengers, passengers on one side of the car are going to have to squeeze to get out.

    Essentially it can be hard to tell if I'm perfectly parallel with the garage walls and whether I'm off center, or rather if I'm within tolerance to back in even if the angle isn't perfect.

    I've looked into building something like range lights [1], but I don't think the math scales down to short distances. Plus if I'm looking in the rearview mirror or my backup camera, neither of which are perfectly aligned with the direction of travel, that might mess with optical navigation aids.

    I might have to dig into this moire approach to see if it would be more feasible.

    Yes, obviously this is a minor inconvenience that I'm able to deal with on a regular basis, but it's fun to theorycraft.

    1: https://en.wikipedia.org/wiki/Leading_lights

    by devanl
  • Many runways have something called PAPI (precision approach path indicator) which does something similar. Basically you have four (or two sometimes for less precise version) lights which appear either red or white depending on whether you are high or low on the glidepath and you aim to get two reds and two whites - more whites means too high, more reds too low.

    I can see that this would be not very intuitive for left/right guidance but are similar systems used in ship navigation?

    by dbuxton

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