North Korean military units jammed Global Positioning System signals Friday in some parts of South Korea, the government believes.
A government source on Sunday said intermittent GPS failure occurred in northwestern base station coverage areas such as Seoul, Incheon and Paju last Friday. "We suspect the interference was caused by strong jamming signals sent by the North."
The North first attempted to jam GPS signals last August during joint South Korea-U.S. military exercises and the latest attack apparently targeted the current "Key Resolve" drills, intelligence agencies say.
The North has two types of GPS jamming devices -- one imported from Russia in the early 2000s and an adapted version. For three to four years it has been circulating a sales brochure for its own version in the Middle East.
The vehicle-mounted device imported from Russia is capable of jamming GPS signals from 50 to 100 km away. The North Korean-made jammer has similar capabilities but is cheaper. An intelligence report says the North recently imported a new 24-Watt jammer from Russia that is capable of interfering with GPS reception within a radius of 400 km, which means it can cover nearly all of the Korean Peninsula.
The devices are targeting mainly the U.S.' Tomahawk and South Korea's cruise missiles or their Joint Direct Attack Munition (JDAM) bombs. But most of the weapons are capable of avoiding signal interference since they use military codes.
The South Korean and U.S. militaries use missile and bomb guidance systems alongside inertial navigation systems. Their accuracy could suffer if only the INS is used. Once the GPS devices are jammed, it would be difficult to locate the precise position of enemy ships or aircraft and could result in missiles or bombs hitting the wrong targets.
A military source said, "We've suffered no significant damage from the North's GPS jamming operations, but missiles or bombs could of course be affected."