In late March South Korea discovered that North Korea had applied off-the-shelf UAV components to produce some smaller propeller driven UAVs. Soon it was revealed that this program was quite extensive and had been around for a year or more.
Although the two different designs (two had a delta wing while one had more conventional straight wings) have been encountered so far both used many of the same parts. Some of the internal components contained markings indicating North Korean origin. Thus is was concluded that the two small (1.9 meter/six foot wingspan) UAVs were definitely North Korean and used commercially available Chinese and Japanese components that any tourist could walk into a store and buy. These components are cheap, rugged and reliable and could spend over an hour in South Korea taking photos. There are cheap and reliable night vision cameras that would fit in these UAVs.
One UAV was found March 31st on one of the islands near the maritime border with North Korea. The other one was found south of the DMZ on the 24th. The UAVs carried high resolution cameras that took pictures when over certain GPS coordinates. The photographs were about the same resolution you can get from Goggle Earth, but with these UAVs you can get photos more recent than most found on Google Earth. The digital photo files taken from one UAV included the presidential compound and some military facilities. The other one was photographing military facilities on the island. Soon after all this was announced in early April a civilian came forward and revealed that he had found a third such UAV in October 2013, but was not aware that it was North Korean. He led troops to where he found it and said the camera on board had been ruined by rainwater but that he removed the memory chip a looked at the photos (they showed a local dam and nearby coastal terrain). The man then erased the memory chip and reused it for his own camera.
UAVs this small are hard to spot with radar if they come in very low (under 100 meters/330 feet). Most importantly these UAVs appear to operate automatically and do not transmit photos back to the ground but store them onboard until the UAV comes back, completing its pre-programmed flight and using a parachute to land. Thus you cannot detect these UAVs via signals sent or received. They don’t make much noise but when flying under the radar (under 100 meters altitude) you could see and hear it as it went by at about 150 kilometers an hour.
South Korea is now upgrading its aerial surveillance to handle this new (but not unknown) threat. Israel has a similar problem and has developed technology to deal with it. Since Israel sells a lot of military gear to South Korea, it was no surprise that ten Israeli radars were soon ordered. Meanwhile the government is considering offering rewards for civilians who find these UAVs since North Korea appears to be using a lot of them and for at least six months.