Slashdot Mirror

← Back to Stories (view on slashdot.org)

Seeing Buildings Shake With Software

Posted by samzenpus on from the whole-lot-of-shaking-going-on dept.

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.

3 of 21 comments (clear)

  1. camera shake? by calzones · · Score: 3, 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.

    --
    Asking people to think is like asking them to buy you a new car
    1. Re:camera shake? by Anonymous Coward · · 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.

    2. Re:camera shake? by Whiternoise · · Score: 2

      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 recent submissions, tons of second or third hand sources that aren't terribly useful.

      http://people.csail.mit.edu/mrub/vidmag/: Original source for Eulerian video magnification