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Comment by gavinpc | Hacker News Reader

What exactly are the implications of this for construction engineering, which must already have some way of measuring vibrations?

I.e. does this measure something previously unmeasurable, or is it just that the visualization provides an extra channel for interpreting the data?

Or is it that it would make this kind of tool available to anyone with a digital camera?

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The vibrational modes of a structure are a sort of signature. When it changes, that means something in the structure has changed. Perhaps a beam has rusted or buckled, or bolts have come loose, or concrete has cracked. This is traditionally tested by placing accelerometers in the structure, but it might be much cheaper if you could do it with a camera.

A big part of it is that measuring the vibrations of large structures, like buildings or bridges, can be inconvenient and expensive. There are limited cases where you can measure new stuff with video simply because you don't have to touch the object or shine a laser at it, but the big win is that by making vibration measurement cheap and simple/convenient, it means you can do a lot more of it. We can start taking more measurements on more structures, which will tell us where we should put resources to rebuild infrastructure.

It might also make quality assurance/ product testing cheaper but that's less save-the-world :-p

It's kind of the last option.

This kind of analysis is already done and important, but usually it takes installing a lot of sensors and giving an impulse to the structure. I have actually worked on a company that did this, using strain gauges.

The fact that this is one using a commercial camera is kind of impressive. I'll take a look on the papers someday, but the obvious way to do this would be to have a framerate at least the double of the frequencies being measured.

Being able to determine frequencies much higher than sample rate not only is non-trivial, but also alleviates immensely the cost of these measurements.

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