MarketWatch reported earlier this month in an article that DJI filed a patent infringement lawsuit in federal court against Yuneec International Co. Ltd. and Yuneec USA, Inc., saying its drones infringe on two DJI patents, including one for target tracking.

The gist of the dispute is that that Yuneec announced last year at the International CES in 2015 the debut of its $1,300 drone, the Typhoon H, that can detect objects in its proximity to prevent collisions and track subjects and calls it "Watch Me". However DJI's Phantom 4, out in March, calls this feature “Active Track,” which allows the Phantom to follow a subject by tapping the subject being monitored from the drone's onboard camera on their smartphone screen. When the subject moves, the drone follows it, keeping it centered in the camera's frame.

Here's a link to a PDF of the court complaint that was filed by DJI.