Seeing Buildings Shake With Software 21
mikejuk writes: In 2012 a team from MIT CSAIL discovered that you could get motion magnification by applying filtering algorithms to the color changes of individual pixels. The method didn't track movement directly, but instead used the color changes that result from the movement. Now another MIT team has attempted to put the technique to use in monitoring structures — to directly see the vibrations in buildings, bridges and other constructions. Currently such monitoring involves instrumenting the building with accelerometers. This is expensive and doesn't generally give a complete "picture" of what is happening to the building. It would be much simpler to point a video camera at the building and use motion magnification software to really see the vibrations and this is exactly what the team is trying out. Yes you can see the building move — in real time — and it seems to be a good match to what traditional monitoring methods say is happening. The next stage is to use the method to monitor MIT's Green Building, the Zakim Bridge and the John Hancock Tower in Boston.
camera shake? (Score:4, Interesting)
Accurately and precisely canceling out camera shake (indeed the movement of the building/foundation where the camera itself sits too) on something like this would seem to be a big deal.
I guess instead of having accelerometers on the building they put them on the camera? Article didn't really get into this aspect.
Re: (Score:2)
The camera's own motion should produce an identical effect across the field of vision, for which the software should be able to control. The motion of objects in view, however, will differ relative to other objects in the field, and the algorithm likely checks for difference between subpixel color change in different regions of the image.
Re: (Score:1)
It works on *colour* changes in the building (because og lighting reacting to the motion I presume). Your local camera shake is not going to change the lighting on the building.
Re: (Score:2)
This is a mystery to me... color changes. The building changes color as it moves?
We need a better TFA. The one linked explains pretty much nothing.
Someone mod this guy up too.
Re: (Score:3)
No, the building stays the same colour. Very simply, consider a particular feature on the building. The location of that feature will shift between adjacent pixels in the image if the building moves relative to the camera. When this happens the pixels change colour (e.g. a 'sky' pixel might now be a 'building' pixel).
The technique can be exploited for other things like blood flow, but in general things don't change colour as they move - unless they're travelling really fast
And I've noticed this a lot on rec
Re: (Score:1)
You're not being more precise. They're working with downsampled, post-bayer images. This isn't a cute hack around bayer patterns, it's hard math that's explained in the paper.
Re: (Score:2)
It's similar to moire pattern analyses [wikipedia.org]. Moire patterns have been used in position sensors for over a decade. In an old job I worked with a Heidehain moire pattern sensor that gave reliable contactless sub micrometer position data.
Go to one of the higher floors in the Sears Tower (Score:2)
On a windy day, the whole building sways. On the upper floors, you can really feel it. Last week it was so bad that we were getting sea sick from the motion.
Terrible soundtrack (Score:2)
I really wanted to look at the video and learn about this thing, but the soundtrack is so bad... I had to give up when it got to the "solo" that starts around 0:38. It sounds like they taped some random person who tried a few keys on a Casio keyboard on display at radio shack.
I think the chilling screams of dogs being skinned live would have been less distracting.
Someone should find the person who picked the soundtrack and pee on the windshield of their car.
John Hancock, Boston (Score:2)
Old (Score:2)
Saw this several years ago. https://www.youtube.com/watch?... [youtube.com]