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Is there a reason why very little information showed up from the legs? Are jeans just great at absorbing but not reflecting wifi signals?
by JusticeJuice 11y ago
Is there a reason why very little information showed up from the legs? Are jeans just great at absorbing but not reflecting wifi signals?
- Jach 11y agoThe problem is that legs make poor backwards reflectors due to their shape, so the reflected signals aren't detected since they're sent elsewhere. Though the material can make a huge difference too. (e.g. wool and nylon can significantly reduce the reflectivity, as can the presence of wrinkles.) The best reflective part of the body is the torso (especially the back) since it's relatively flat.
- corvus_sapiens 11y agoSo recognition doesn't work if it was calibrated while you were wearing different clothing? That kills some of the use cases.
- Jach 11y agoThe wall being made of reinforced concrete also kills a few use cases. But human detection isn't hopeless in general. You can do pretty well (even gender distinction) by having a physically based model of what you're expecting, e.g. humans, on the ground level instead of at some angle, within a certain range, potentially moving but you can detect heartbeats too, and there are models of how the human body behaves at rest and while moving. (Edit: the assumption of movement really helps a lot since you can diff samples and subtract out all the static bits. So even if clothing attenuates the signal by x%, x < 100, if the human's the only thing in the scene that's moving you're ok.) (I'm actually impressed/jealous with what they accomplished since it was something I tried and failed to do alone for a school project based on http://ocw.mit.edu/resources/res-ll-003-build-a-small-radar-system-capable-of-sensing-range-doppler-and-synthetic-aperture-radar-imaging-january-iap-2011/ http://ocw.mit.edu/resources/res-ll-003-build-a-small-radar-...)