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Posted by: Heath Robinson Oct 3 2009, 12:31 AM

They've developed http://scienceblogs.com/sciencepunk/2009/10/scientists_use_wifi_network_to.php.

NOBODY IS SAFE, THEY CAN ALREADY SEE YOU! RUN WHILE YOU STILL CAN!

Posted by: Karoline Oct 3 2009, 12:50 AM

Except at best they can tell that -something- moved between two wireless devices. I mean I guess you could set up tons of wireless devices in your house to make a motion detection system (Though an actual system would likely be easier), but it wouldn't help anyone else. The government couldn't spy on you with it (Unless they hacked into your computer, at which point you likely have more problems than them knowing if you're home or not.)

Still a cool discovery.

Posted by: Heath Robinson Oct 3 2009, 02:22 AM

Consider... a hundred devices (I assume that's not ridiculous by 2070 standards). That is, 9 900 possible connections you can poll. All of those are fuzzy laser tripwires that penetrate walls.

You will be able to get size off that (though you can get a rough estimate of size off a single edge anyway). You might even be able to interpolate the data to get a rough pose estimate. Sure, it might not tell you who the person is. More importantly, you have a high density mesh network that can also route data at the same time as detecting movement.

Posted by: Karoline Oct 3 2009, 02:30 AM

Oh, well yeah, if your talking in 2070 SR universe yeah. I thought you meant in today's world.

And you really couldn't determine the size from just one link, because you would have to know speed. You can tell how long the object blocked the signal, but not how quickly the object was moving. It could have even stopped for a few minutes there.

Posted by: Heath Robinson Oct 3 2009, 03:09 AM

The radio signals travel along elliptical paths if I'm reading things correctly. Something passing near the edge between a node pair will disrupt some, but not all, of the potential paths between the nodes. You can use precomputed statistical information to determine how much occlusion there's been. For smaller items this is sufficient to calculate the rough mass (or maybe silhouette area), and you can interpolate from multiple edges for larger items.

Posted by: Karoline Oct 3 2009, 11:15 AM

They travel along elliptical paths, but you'll only get one line between two points I think. Otherwise you would only need 3 or 4 devices to get a rough picture of someone, as opposed to the mesh that they spoke about.

Posted by: Drraagh Oct 4 2009, 10:37 PM

So, probably in the Shadowrun world, it's possible that you could get it to the point of the Thermographic wall radar from Robocop where he takes out the guy holding the mayor hostage.

Posted by: Weaver95 Oct 4 2009, 10:45 PM

assuming nobody has slathered walls with wifi blocking paint or other materials, yes.

Posted by: Heath Robinson Oct 4 2009, 11:55 PM

You get a bunch of potential paths, but the antenna doesn't receive each path independantly - it sums all of the signals from all of the paths, which turns a potential bitmap into a single scalar. You can tell some information about the object passing through the edge (though technically the summation means that you can only get the proportion of the edge that is occluded).

One of the cool things I could have sworn I mentioned was that you can use an airborne occludent to generate a rough map of an enclosed space if you pump it into the target region from a single point. You need merely watch it with this system as it permeates through the environment.