Moire Patterns Guide Ships: A Hands-On Build and Critique
Guiding Ships with Moire Patterns
Inspired by Tom Scott's video, I built a moire-pattern navigation light following a 1986 patent. The device projects a narrow beam that shifts with viewing angle, offering intuitive steering cues. While it works as advertised, I argue that for harbor navigation, a simpler three-light system is safer and more practical, as it indicates actual danger rather than deviation from an ideal line. The moire system shines for marking narrow targets like submarine cables.
If I were a pilot I think I'd much prefer a system like the 3 lamp, that lets me know when I'm actually in danger, rather than a system letting me know I've deviated from a line someone drew on a map.
- JR1427
I've used an INOGON entering a marina in the UK, and it really did have a very narrow dredged channel, not a wider safe area.
One problem with lights or marks is that they can be very hard to see. At night, there are lots of other lights to confuse things, and it can be easy to mistake on light for another.
- dbuxton
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?
- devanl
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.
- tomalpha
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.
- bonzog
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.