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Old 10 June 2015, 01:42 PM
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A Turtle Named Mack A Turtle Named Mack is offline
 
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Cell Phone Wi-Fi signals can help count people in a crowd

A Wi-Fi signal can be used to count the number of people in a given space, leading to diverse applications such as energy efficiency to search-and-rescue operations. This approach does not require people to carry Wi-Fi-enabled devices for them to be counted.

http://zeenews.india.com/news/net-ne...d_1610193.html
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Old 10 June 2015, 03:02 PM
jimmy101_again jimmy101_again is offline
 
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As described in the cite I can see counting people in public places as very doable and useful. The search and rescue possibility really seem like a stretch.
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Old 10 June 2015, 04:34 PM
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Quote:
Originally Posted by jimmy101_again View Post
As described in the cite I can see counting people in public places as very doable and useful. The search and rescue possibility really seem like a stretch.
I get the impression the 'search and rescue' application was the ability to know how many to look for after a disaster. If you keep a continuous count and can pull the info, then you know how many were in the building/area to be rescued.
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Old 10 June 2015, 06:08 PM
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A Turtle Named Mack A Turtle Named Mack is offline
 
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Yeah, the real issue there is whether the people have to be moving for the algorithm to work. At one point it refers to sensing people walking, but elsewhere, it makes it sound like the mere presence of bodies can be determined from the way Wi-Fi signals are scattered by bodies. If it is the latter, then you could determine how many people were under rubble, in a burning structure, etc. This is still a work in progress, though.
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Old 10 June 2015, 06:24 PM
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AIUI, WiFi is a high enough frequency that it will bounce off many things, such as chunks of concrete or furniture, especially metal file cabinets or shelves.
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Old 10 June 2015, 08:50 PM
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It also specifically says an estimate. This sounds like it might be useful for getting, say, a good estimate of the number of people who showed up for a rally on the National Mall. For keeping an accurate count of how many people are in a building may be a stretch. RFID badges would take care of that problem a lot easier.
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Old 11 June 2015, 12:12 AM
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Not to be a negative Ned, but WiFi signals are pretty short range and the detection currently requires two WiFi spots so you'd be limited to "cells" of 40 meters or less.
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Old 11 June 2015, 01:38 AM
jimmy101_again jimmy101_again is offline
 
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It sounds like the system would not be accurate enough to be useful to tell rescuers how many were in the building before some catastrophe (like an earthquake). I wouldn't think there would be much difference to a rescue team in an estimate of 3 plus/minus 4 or 9 plus/minus 4 or 50 plus/minus 10. In all cases you would need to start digging.

I think there is pretty much zero possibility of using wi-fi through a pile of ruble to locate trapped individuals. Wi-fi just doesn't penetrate solids well enough, and the system counts on scattering and absorption of the signal in a mostly empty space to detect people.

Sound systems like sonar (both active and passive) seem a lot more practical.

I wonder if a wi-fi system could help locate a trapped individual if they had a wi-fi active device like a smart phone?
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Old 11 June 2015, 01:42 AM
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Originally Posted by GenYus234 View Post
Not to be a negative Ned, but WiFi signals are pretty short range and the detection currently requires two WiFi spots so you'd be limited to "cells" of 40 meters or less.
In the case of a collapsed building 40 meters is huge, especially if you could get to say 1 meter resolution. I don't think wi-fi will work but not because of a 40 meter range restriction.
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Old 11 June 2015, 02:24 AM
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Quote:
Originally Posted by A Turtle Named Mack View Post
Yeah, the real issue there is whether the people have to be moving for the algorithm to work.
I think it does require some movement but the vehicles they've got for their WiFi can move around, too. The same reseachers have already demonstrated they can work through walls to map interiors with a similar (same?) pair of robots. WiFi is so cheap and small and low power it seems like including a more developed version of this (along with visual, lidar, sonar, etc) in a search and rescue robot package would be more than feasible.
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Old 11 June 2015, 03:07 PM
jimmy101_again jimmy101_again is offline
 
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Quote:
Originally Posted by A Turtle Named Mack View Post
Yeah, the real issue there is whether the people have to be moving for the algorithm to work. At one point it refers to sensing people walking, but elsewhere, it makes it sound like the mere presence of bodies can be determined from the way Wi-Fi signals are scattered by bodies. If it is the latter, then you could determine how many people were under rubble, in a burning structure, etc. This is still a work in progress, though.
I suspect it can only detect stationary people when the system already has a "map" of the area without anyone in it. So in a normal room type space it might be able to detect a person sitting at a table even if they aren't moving much. If the system doesn't have a "map" of the area then it wouldn't be able to detect stationary people, only movement.
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Old 11 June 2015, 03:19 PM
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Quote:
Originally Posted by jimmy101_again View Post
In the case of a collapsed building 40 meters is huge, especially if you could get to say 1 meter resolution.
The range limitation was addressing Darth CCR's idea to use it to count people in the National Mall.
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