Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Using the railway network as a flatbed scanner [video]

media.ccc.de

Post reply on HN
Print view View original

31–37 of 37 posts

Re: Using the railway network as a flatbed scanner [video]

#31

Post by fnord77 »

Terr_ wrote: post #15

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…

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

Re: Using the railway network as a flatbed scanner [video]

#32

Post by spl757 »

sciencesama wrote: post #4

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

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.

Re: Using the railway network as a flatbed scanner [video]

#35

Post by brainwad »

trillic wrote: post #30
fhars wrote: post #22

Earlier quoted context omitted.

In a Faraday cage?

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.

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.

Re: Using the railway network as a flatbed scanner [video]

#36

Post by pvillano »

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.

Post reply on HN