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Deborah Pickett

The idea is that all the lights on a given building should flash together. That way, an aviator can visualize the solid space between lights that blink the same way. Blink same? Don't fly. Blink different? That's a gap.

And that's how it worked for a while. A building's owner would wire all the lights together and feed them with a centralized oscillator signal.

Later on, when wire got expensive and buildings got taller, they switched to short-range radio, with one transmitter sending the blink signal, and each light having a receiver in it.

This worked fine, because all oscillators will drift eventually, so every building gets a different blinking pattern.

Then GPS happened.

24 Aug 2023 at 1:43 | Open on old.mermaid.town
36 comments
Deborah Pickett

Now you can buy a beacon like this one, which is standalone and has a GPS receiver in it. Anyone who's cobbled together an NTP server will know that the GPS system can provide microsecond-accurate time as a side-effect.

So these beacons don't care where they are, but they all know exactly when "now" is. And they can synchronize to each other by synchronizing to the GPS signal. It makes maintenance _so_ easy.

L-864 Synchronized GPS Beacon with Photocell and flasher.
24 Aug 2023 at 1:47 | Open on old.mermaid.town
Bjornsdottirs

@futzle the beacon knows when it is because it knows where it isn't.

24 Aug 2023 at 1:48 | Open on mastodon.top
Deborah Pickett
Bjornsdottirs

@futzle ... come to thisk of it, with GPS being GPS, that... might almost be how that fucker works

24 Aug 2023 at 1:53 | Open on mastodon.top
sabik

@ellenor2000 @futzle
The more modern approaches to celestial navigation (with a sextant) also work on where you aren't

24 Aug 2023 at 2:00 | Open on rants.au
Kyle Brown

@ellenor2000 @futzle this is basically true. With enough satelites, you have enough equations of location that you can solve for time

24 Aug 2023 at 4:10 | Open on kind.social
Deborah Pickett

Trouble is, these beacons come preset to a particular blink pattern, and when you buy one (ten, fifty) you're probably not going to bother to change the blink pattern in them all. What if you forgot to do one?

So what happens is that your building is synchronized to GPS, and so is your neighbour's building, and so is _their_ neighbour's building. The whole city flashes once every two seconds, like clockwork.

Completely negating the whole point of having one blink-pattern per building, and rendering aviation around tall buildings unsafe again.

It's an accidental own-goal, brought about by the efficiencies of global, perfect, timekeeping.

(end)

Trouble is, these beacons come preset to a particular blink pattern, and when you buy one (ten, fifty) you're probably not going to bother to change the blink pattern in them all. What if you forgot to do one?

So what happens is that your building is synchronized to GPS, and so is your neighbour's building, and so is _their_ neighbour's building. The whole city flashes once every two seconds, like clockwork.

24 Aug 2023 at 1:51 | Open on old.mermaid.town
Deborah Pickett

(Postscript: a few of us here on the Fedi worked this out from first principles after someone noticed that the lights on several buildings in their city were all blinking together. It was a great piece of detective work.)

24 Aug 2023 at 1:52 | Open on old.mermaid.town
πŸ‡΅πŸ‡Έ Mari :nb_crossbow:

@futzle hi yes hello I was part of an art project that made use of this idea and I think of it every time I see groups of blinky lights ^_^

kickstarter.com/projects/96622

we ended up building our own lights and controllers and firmware for it, mostly because they would also - about every 10 minutes - display the speed of a seismic wave thru that particular soil geology github.com/ArdentHeavyIndustri

24 Aug 2023 at 2:09 | Open on spanner.works
Francis πŸ΄β€β˜ οΈ Gulotta
Seirdy

@bouncinglime @futzle That sounds awesome. It’s hard for me to find photos/videos of the finished piece; would you happen to have any?

24 Aug 2023 at 3:00 | Open on pleroma.envs.net
Umberto Ecco

@bouncinglime Wow this is so cool! I'd heard about some of your projects before but not this one. Wish I'd been there to see it!

24 Aug 2023 at 4:33 | Open on beach.city
πŸ‡΅πŸ‡Έ Mari :nb_crossbow:

@nyankat thanks! it was one of the coolest things I've ever been part of honestly πŸ’œ and yeah definitely one of those "you had to be there" types

24 Aug 2023 at 4:47 | Open on spanner.works
JodieM

@futzle ah yes I did notice synchronised blinking a few months ago. Thanks for that.

24 Aug 2023 at 2:16 | Open on aus.social
Misinformation-Superhighwayman

@futzle Thankyou for explaining this! I've tried to take photos of the Melbourne CBD skyline at night and noticed that many of the buildings have rooftop navigation lights in synch, a few switch with the same period but a different part of the cycle, and a few others appear to drift over time so they appear to harmonise sometimes but not at other times.

24 Aug 2023 at 2:24 | Open on aus.social
Francis πŸ΄β€β˜ οΈ Gulotta

@futzle This is a wonderful dive into something really interesting πŸ‘

Thank you

24 Aug 2023 at 2:50 | Open on toot.cafe
DELETED

@futzle

I worked on systems which mass monitor extremely large amounts (>XX% of the total market in the US) of beacons.

This synchronization caused issues (outages, slowness, downstream issues) at one point because they all happen at the same time in a geographic location, and a mass influx of updates come in then.

It's quite interesting stuff and that is still one of the cooler projects I've built from the ground up :)

24 Aug 2023 at 3:27 | Open on social.treehouse.systems
Placebo

@futzle
Wow! Thanks for posting this. Last week I drove to Portland and we passed a bunch of wind farms. I couldn't figure out why someone would go through the effort to synchronize the beacon lights on all the windmills. It never occurred to me that it was a sign that someone *hadn't* taken any effort.

24 Aug 2023 at 3:59 | Open on defcon.social
DELETED

@futzle Thank you! That was super-interesting!

24 Aug 2023 at 5:07 | Open on toot.site
Irenes (many)

@futzle oh how cool and upsetting! thank you :D

24 Aug 2023 at 5:43 | Open on mastodon.social
Jorge

@futzle Very interesting thread! I can't help but wonder: if they have GPS, they not only sync but can also get coordinates of their location, ignoring height. So assuming resolution of <10meters and assuming buildings are usually >=5meters wide in any direction and have some space between them, wouldn't it be trivial to use the beacon's location as a seed to sync up all the lights of a building but ensure they are different from the beacons of the buildings next to them?

24 Aug 2023 at 5:53 | Open on mas.to
Jorge

@futzle sorry never mind what I just said @weaselx86 had already pointed it out

24 Aug 2023 at 5:57 | Open on mas.to
Deborah Pickett

@jorgeyanesdiez I can't think of a way to do this without the beacon needing to have a copy of a map. Consider in a dense downtown: the corners of different skyscrapers may be across a street only 20 m wide but the buildings themselves fill a 200 m block. Closeness is actually the _opposite_ of what you want.

24 Aug 2023 at 5:58 | Open on old.mermaid.town
cratermoon

@futzle Nobody building the lights thought to put some kind of random jitter around the timings?

24 Aug 2023 at 3:07 | Open on zirk.us
Deborah Pickett

@cratermoon How do you ensure that the ten lights you bought today for your new building all have the same jitter? Safest to engineer out that opportunity for user error.

24 Aug 2023 at 3:09 | Open on old.mermaid.town
cratermoon

@futzle Ah, I see, I didn't understand how multiple beacons/building should work, thanks for clarifying.

24 Aug 2023 at 3:30 | Open on zirk.us
Willow :trans_flag:

@futzle@old.mermaid.town This is super interesting. I'm a certified pilot, and I've never heard about these flashing patterns before!

24 Aug 2023 at 3:45 | Open on blahaj.zone
Alexandra Magin πŸ³οΈβ€πŸŒˆ

@futzle Oh, fascinating. I'd noticed this synchronization with things like AM broadcast antenna tower arrays before, which maybe is a lot like a single building conceptually, but I hadn't noticed city skylines in recent years.

24 Aug 2023 at 4:11 | Open on hachyderm.io
Weasel

@futzle
Couldn't they manufacture them to blink at a time based on the bottom bits of their latitude/longitude? So that lights on the same building would blink nearly simultaneously, but lights on different buildings would blink at discernibly different times?

24 Aug 2023 at 4:11 | Open on mastodon.social
Deborah Pickett

@weaselx86 Thank goodness buildings are built on a grid 131072 to the degree! πŸ™ƒ

But seriously, they are already made with customizable blink timing patterns, but the fact that you see entire cities blinking like one giant Christmas tree tells you how much this feature is being used.

24 Aug 2023 at 4:16 | Open on old.mermaid.town
Weasel

@futzle
Right, the lack of use of the customization is why I was looking for a manufacturing default that might accomplish the desired purpose.

Saying "bottom bits" was cavalier of the details; but the GPS has the location, and I'm confident it's possible to develop a location-based algorithm that could distinguish buildings reasonably well without requiring they be build on a grid. It seems like the manufacturers could improve the situation without cooperation from the field.

24 Aug 2023 at 4:35 | Open on mastodon.social
Umberto Ecco

@futzle similarly, back before GPS, radio altimeters, etc, if two flights were accidentally assigned to the same flight level, differences in their barometric altimeters meant they would probably miss each other even if they got quite close.

So after the tech advances, everything is right at the altitude it’s been put at and the danger of collision went up for a while.

That’s fixed now, but only because they built an entire traffic avoidance system to avoid this (TCAS)

24 Aug 2023 at 4:15 | Open on beach.city
Guglielmo

@futzle I suspect that would be Idiocracy with a scientist instead of a common man

24 Aug 2023 at 4:21 | Open on mastodon.uno
erik

@futzle Huh, TIL! I have a tall transmission tower out my back window and often wonder how they sync the beacons. I always thought that perhaps they were using the 60Hz freq of mains AC to do it, but it’s cool to know that these GPS beacons are a thing.

24 Aug 2023 at 1:51 | Open on mspsocial.net
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