Using the railway network as a flatbed scanner [video]

Posted by Jimmc414 3 days ago

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Comments

Comment by Terr_ 2 days ago

Random thought: If you stick a very small adhesive mirror to the outside window before boarding, then footage "looking down" at the regularly-spaced railroad ties could contribute to information about the current speed and acceleration.

Well, on a straight section anyway, if you turn, the inner/outer edges will appear differently-spaced...

Wouldn't do anything positive in terms of suspicious staff though. They might think it's like some kind of heist-movie that will involve a specialized glass cutter making a circle on the window.

Comment by fnord77 2 days ago

and then paint certain ties white and other black, now you have the world's biggest barcode

Comment by rnewme 2 days ago

Why not just use phones GPS?

Comment by Terr_ 2 days ago

In the presentation they mention they are using GPS, and also an accelerometer.

Comment by fhars 2 days ago

In a Faraday cage?

Comment by 2 days ago

Comment by trillic 2 days ago

with any view of the sky multi-band gps is damn good these days, my watch gets good locks through airplane windows even in the middle seat. In aluminum 737s, not compostite frames.

Comment by brainwad 2 days ago

Train carriages, especially older ones, often have metallic windows so they are even worse than a typical plane. Even right up against the window, with the phone directly against it I have failed to get any lock on some trains.

Comment by pvillano 1 day ago

One fun thing is that the camera is that the projection is perspective in the vertical axis and othographic in the horizontal axis. That's why "zooming out" is done by squashing the image horizontally.

Through a regular camera, a person near the track, and a statue 16x times as large but 16x further away would have the same apparent size. They would show up as the same number of pixels in width and height. However, with a line scan camera, the apparent width of objects does not change with distance. Those same objects would have the same apparent height, but the width of the larger statue would be 16x.

You can also think of the camera of having a virtual sensor that's a few cm tall and a variable width, from meters to miles wide. It can only capture scenes as wide as the virtual sensor, unless it's being rotated.

Comment by jo-m 2 days ago

Basically the inverse of https://daniel.lawrence.lu/photos/ or https://trains.jo-m.ch/ ;)

Comment by fdb 2 days ago

Also reminds me of the work by Adam Magyar, high-speed filming of people as the train arrives:

https://vimeo.com/123336197

https://www.magyaradam.com/wp/?page_id=596

Comment by contr-error 2 days ago

The former is in the prior art section at 2:24!

Comment by m463 2 days ago

I've played with panorama mode and tried both of these (1 - panorama of moving train passing platform, 2 - panorama out window of a moving train)

...and both got the same weird artifacts, as it piled "similar" slices together then jumbled up "complex" slices.

Too bad they can't have a toggle for time-slice based panorama vs scene-based panorama. or maybe turn on accelerometer optimizations or not.

Comment by fudged71 2 days ago

Free slit scan photograph apps exist

Comment by inigyou 2 days ago

Random thought: if you stick a camera to each train you might know their location better than Deutsche Bahn does.

Comment by andrelaszlo 2 days ago

Since at least you know where it was when you put the camera on it?

Comment by slipheen 2 days ago

I love this so much! This is such a cool hack, just for the sake of it. Amazing hacking and amazing art!

In the preso, she has said the full size output is on the website-

can anyone see what that link is? I didn't find it on the video page, but I might've just missed it.

Comment by azalemeth 2 days ago

http://philo.gay/linecam/gallery.html -- it's linked within the middle of the talk.

Comment by contr-error 2 days ago

https://philo.gay/linecam/

Comment by m463 2 days ago

When I read the title I thought of another IDEA that I've had bumping around in my head that would be pretty cool.

Put down two model railroad straightaways next to each other, with two locomotives, use them as a base to attach a 3d-printer arm across and "print" a model railroad diorama, incrementally moving the locomotives to print each slice.

In other words, a flatbed 3d printer where one axis is the locomotives moving across your railroad layout. I think it could rejuvenate model railroads if you could print mountains, towns, streambeds, roads, etc...

Comment by dhosek 2 days ago

A big part of the joy of model railroading is the building of such things, at least for some people.¹ It’s less about the product than the process. That’s a big part of why things like kitbashing and scratch building are popular. Finding a way to construct something out of nothing.

⸻

1. Yes, there are people who are more into the operations side of things, but I think for most model railroaders it’s as much about the building as the running.

Comment by m463 2 days ago

You could take this as far as you want.

Like you could put down the foundation of everything, then manually add the grass or the buildings or pour epoxy water.

or you could print the roadbeds and the buildings and just paint everything yourself.

I wonder if you could create those "standard sized diorama" things that people take to railroad conventions that people hook together with their neighbors who also have standardized layouts.

Comment by inigyou 2 days ago

You need a fairly precise movement mechanism for 3D printing.

Comment by fragmede 2 days ago

Good thing we have those!

Comment by inigyou 1 day ago

In your model railway? It can move the trains with 0.05mm precision?

Comment by 2 days ago

Comment by rollulus 2 days ago

From experience: the iPhone’s panorama photo mode works to take pictures like this from a train.

Comment by lalalandland 2 days ago

Using the camera as a scanner has a long history in satellite cameras and other aerial photography

Comment by 1e1a 2 days ago

This is often called Push broom scanning.

Comment by sciencesama 2 days ago

they need to connect with the skunkworks team, they solved this problem on sr 71 long time back !

Comment by naikrovek 2 days ago

well, they used film, which made it very easy to implement.

this is easy with a roll of film and a slit for an exposure window. you have the lens and the aperture and focus and all of that, but instead of a full frame, you mask it down to a small slit. slowly pull the film across the slit when it's time to capture your target. captures are limited only by how much film you can fit on a reel and feed through the camera during flight. I would expect that miles of film could be carried on the SR-71 without problems. You'd need (I assume) some custom machines to develop that film properly and to produce prints, but that's not a challenge for an entity that can design and build an SR-71.

Comment by spl757 2 days ago

That plane still looks bad-ass today. I heard that they just leak oil constantly on the ground before the engines warm up and the metal expands the the O rings make a seal.

Comment by ted_dunning 2 days ago

It would have been pretty easy to use a horizontal line scanner to get image speed.

In any case, it seems that using a full frame video would be much easier to post process since frame to frame correlation tells you everything you need to know about motion.

Comment by xnx 2 days ago

One of the first scripts I vibecoded did exactly this. It works well, but is limited by framerate when there's high motion.

Comment by mikewarot 2 days ago

The first attempt was with video, but she later switched to exactly that, a 19000 lines per second 2048 pixel line scan imager. It was augmented with 6dof acceleration/gyro sensor, gps, and microcontroller to get the data to a laptop.

Comment by leni536 2 days ago

I'm not sure that video would have been easier to postprocess. At what fps and shutter speed?