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.
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?
> "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?
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.
Moire patterns can also be used as a magnification device, similar to microscope. For example, when two screens having microscopic hexagonal holes are made to slids past each other as a slight angle, one can see large hexagons.
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:
> 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.
Also when you receive Morse code on a radio using a Beat Frequency Oscillator, which is tuned close to but a little off from the IF frequency.
It's also how a Theremin works, using the capacitance between your hand and the pitch and volume antennas to pull the frequency of an oscillator. If you'd like to play with a Theremin I might be selling mine - I haven't touched it for months...
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.
So... seat position memory has been a thing in cars for many years now.
Given the importance of eye position, the standardization of Airbus cockpits, the near-universal use of EFBs and Airbus's penchant for automating absolutely everything... I'm kind of surprised that a reference seat position for each pilot isn't measured when pilots go in for sim time, saved in each pilot's EFB and then automatically applied when they sit down.
Airlines are always looking for ways to reduce ground time, and it seems like that would be an easy way to save a minute at every turn.
> Typically a harbour doesn’t have one razor-thin path of traversable water. Instead there’s a clear pathway that you shouldn’t stray too far away from. The Moire system will give steering advice even if you’re in a safe area, but slightly off the main ‘beam’.
You could fix this issue by just having a second lamp (or two grills in front of the same lamp). If the two arrows point in opposite directions, you're safe. If they point the same direction, you're not.
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.
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[ 0.24 ms ] story [ 7.2 ms ] threadI'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
[0] https://en.wikipedia.org/wiki/LORAN
I can see that this would be not very intuitive for left/right guidance but are similar systems used in ship navigation?
> - 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?
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...
https://www.ouruboroi.com/moire
https://www.ouruboroi.com/moire2
https://www.ouruboroi.com/moire3
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.
Also when you receive Morse code on a radio using a Beat Frequency Oscillator, which is tuned close to but a little off from the IF frequency.
It's also how a Theremin works, using the capacitance between your hand and the pitch and volume antennas to pull the frequency of an oscillator. If you'd like to play with a Theremin I might be selling mine - I haven't touched it for months...
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/
Given the importance of eye position, the standardization of Airbus cockpits, the near-universal use of EFBs and Airbus's penchant for automating absolutely everything... I'm kind of surprised that a reference seat position for each pilot isn't measured when pilots go in for sim time, saved in each pilot's EFB and then automatically applied when they sit down.
Airlines are always looking for ways to reduce ground time, and it seems like that would be an easy way to save a minute at every turn.
You could fix this issue by just having a second lamp (or two grills in front of the same lamp). If the two arrows point in opposite directions, you're safe. If they point the same direction, you're not.
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.