Mobile-phone signals reveal rainfall—and maybe a lot more

news @ nature.com: Transmissions wobbles create weather data...

"Research carried out by Hagit Messer and her colleagues at Tel Aviv University in Israel shows that it is possible to gauge rainfall by analysing the signal fluctuations of mobile-phone base stations. The group believes that by using information that is already collected by mobile-phone companies it should be possible to create much more accurate weather models. 'What we are offering is better accuracy and better coverage,' says Messer.

It is a well known phenomenon that rain can affect mobile-phone transmissions: droplets in the air reduce signal strength, with different-sized droplets affecting specific frequencies in the signal. This is so firmly established that base stations now automatically compensate for signal attenuations as the atmospheric conditions change, says Messer, whose work is published today in Science."
(Messer H., Zinevich A., Alpert P. Science, 312. 713 (2006).)
(. . .)
Mobile-phone signals themselves have also been harvested for other information in the past. Some researchers, such as Microsoft's Eric Horvitz, have looked at using such signals as a way of monitoring how much traffic is clogging the roads, simply by using mobile-phone transmissions as proxies for the number of cars. And in 1999 during the conflict in Kosovo, it is widely thought that some sort of disturbances in mobile-phone networks were used to help Serbian forces detect US Air Force F-117 stealth fighters, and shoot one down, when they couldn't be seen on radar.

Remember when the Chinese Embassy was "accidentally" bombed by the US in Yugoslavia? I remember hearing a student being interviewed on KPFA claim he had discovered how, using electronic equipment easily obtained from Radio Shack, one can use distortions of radio waves caused by Stealth Fighters and Bombers to track them. He described it as the planes causing "ghosts" in the TV signals, like when your antenna is not adjusted correctly. Sounded reasonable to me. After Milosevic's residence was bombed, the only radio signals being sent in the area were from the Chinese Embassy's television transmitters. Therefore, to enable our attack to proceed, the Embassy had to be bombed. I've never found mention of this anywhere— on or off the net—but I just found this:

From Pacificnews.org, 1999:

Now, five months later, two newspapers -- the Observer in London, Politiken in Copenhagen -- jointly reported October 17 that several NATO officials and military officers have admitted that U.S. bombing of the Chinese Embassy in Belgrade was deliberate.

The reporters also quoted a NIMA source as saying that the "wrong map" story was "a damned lie."

"Nearly everyone involved in NATO air operations or (radio) signals command knows that the embassy bombing was deliberate," said Jens Holsoe of Politiken, lead investigative reporter on the team.

The seasoned Danish journalist said he could not make sense of the claim that NATO based its targeting on old city maps, but "couldn't figure out in my own mind why NATO would deliberately bomb the embassy."

However, soon after he entered Kosovo with the first contingent of KFOR troops, he met a NATO electronic intelligence (Elint) officer who told him the Chinese Embassy was being used as a rebro (re-broadcasting) center.

"NATO had been hunting the radio transmitters in Belgrade," the officer said. "When the President's (Milosevic) residence was bombed on 23 April, the signals disappeared for 24 hours. When they came on the air again, we discovered they came from the embassy compound."

Oddly enough, I just found this online, from MIT, from 2001:

“Televisions have improved quite a bit, and comb filters have gotten better,” said Duckworth. “On older TV sets, though, when an airplane goes over your house, a reflective wave from the aircraft ends up interfering at your antenna, and you see lines and artifacts on your screen. To the extent that a stealth aircraft does not absorb the wave, the remnants of it still interact with the airplane and result in detectable interference patterns.”

The television analogy is particularly apt, since Lockheed has been working on a project that operates on the same principles as Roke Manor’s anti-stealth system. In this project, called Silent Sentry, FM radio stations and VHF television broadcasts are used to provide the dense network of radio waves that interacts with stealth aircraft. While there are fewer FM and VHF transmission towers than cell phone towers, each individual station transmits much more powerfully. The smaller number of stations would also reduce the computational requirements of the system.