http://www.nytimes.com/2002/06/20/technology/circuits/20SPYY.html For the Spy in the Sky, New Eyes FLYING in his helicopter, Sgt. Frank Sheer of the Orange County Sheriff's Department in Southern California can be literally miles from the action. But that does not mean that he and his co-pilot do not know what's going on. In fact, Sergeant Sheer says they often have a clearer picture of a crime scene than the officers who are there. "We'll be tracking a suspect on a hillside from the helicopter," said Sergeant Sheer, the chief pilot in the Orange County force, "and the deputies climbing up it will be saying to us, `There's nobody here.' We've actually had them step on a guy who pulled up a bush for cover." It's not just having a bird's-eye view that gives Sergeant Sheer and many other airborne police officers, rescue workers, military personnel, and television news and movie crews almost paranormal vision. Nor is it simply advances in optics and cameras. Ultimately they all rely on complex camera stabilization systems that mix mechanical and electronic technologies to produce steady images, even at high magnification, from inherently unsteady craft like helicopters and boats. When officers pursued O. J. Simpson along the freeways of Los Angeles eight years ago, a covey of police and television news helicopters tracked him with stabilized cameras hanging at the sides in their distinctive ball-shaped pods. But most helicopter surveillance is not that dramatic. If the Orange County Sheriff's Department needs a car discreetly followed, Sergeant Sheer can keep tabs on it from 3,000 feet up and a considerable distance behind  a position that would leave most motorists unaware there was a helicopter around, let alone watching them. New systems built around all-electronic motion-sensing technologies are so stable that only the horizon and haze limit how far away observers can be. The use of airborne stabilized cameras to create films or follow athletes in action attracts little controversy. Nor does anyone dispute that the systems allow police officers to capture criminals or rescue people. Some privacy advocates, however, are concerned that the recent proliferation of airborne cameras and the growing capabilities of new systems may mean that anyone who steps outside may unknowingly be a target of an aerial eye. Outdoors, there may no longer be any place to hide. "Because technology affords police what amounts to superhuman vision, that doesn't mean we lose all expectations of privacy," said Barry Steinhardt, the director of the American Civil Liberties Union's program on technology and liberty. "There are lots of innocent people who are going to have their privacy invaded  observed naked in their backyard sunbathing from far away." There is a long history of efforts to produce steady airborne pictures. But in the early years, the results were for the most part dismal. Steven Poster, the president of the American Society of Cinematographers, recalls his first attempt at photography from a helicopter, in the late 1960's. "It was an Illinois State Fair, and the stabilization came from a rope tied around me to the helicopter," Mr. Poster recalled. "I quickly realized that this was not a very good system." While more sophisticated systems existed back then, they did not differ much from Mr. Poster's rope. Known as side mounts, they generally relied on bungee cords and the user's body to isolate the camera. By the 1980's Mr. Poster was a director of photography for feature films and television advertisements, and he had found an answer to his aerial photography problems with a system made by Wescam, a company now based in Burlington, Ontario. "It's the best way to stabilize a camera," said Mr. Poster, who has used the system in films like "Stuart Little 2," which is to be released this summer. The Wescam system used by Mr. Poster's film crews is remarkably similar to the original Wescam developed in the early 1960's by a Canadian subsidiary of Westinghouse as a battlefield surveillance tool for the Canadian military. (Wescam is short for Westinghouse camera.) Eliminating the vibration from the helicopter was the first step and the easy part. The Wescam ball is attached to a helicopter or airplane through a shock absorber that uses springs and other damping materials. "It is tuned for the natural frequencies of helicopters," said Mark Chamberlain, a mechanical engineer who is president and chief executive of Wescam. But eliminating the vibration does nothing to limit three other kinds of movement by the camera: pitch (plunging up and down), yaw (rotating around a vertical axis) and roll (the side-to-side rotation that creates a moving horizon). To deal with these kinds of movements, inventors of the original Wescam turned to large gyroscopes, which create inertia. It is like strapping a large boulder to the camera to stabilize it, yet without all the weight that a boulder would add. Inside the camera ball are three gyros oriented to offset each of the three types of unwanted motion. Motors attached to the camera mount allow an operator within the helicopter to view images from the camera on a video monitor and point the camera as needed. The gyro stabilization system proved so steady that it has not significantly changed over the last three decades. But the system has one significant drawback: the gyros require frequent maintenance. <snip>