Chinese researchers have developed a novel technique for tracking ships at sea using low-resolution, open-source, “free” satellite images. This innovative method, spearheaded by Hong Jun of the Dalian Naval Academy, employs an algorithm to detect ship wake patterns, enabling the identification of vessels that are otherwise difficult to spot.
Despite the satellite images having resolutions of tens or even hundreds of meters—where a large warship might only occupy a single pixel—the team successfully identified a U.S. Nimitz-class aircraft carrier, a Ticonderoga-class cruiser, and an Arleigh Burke-class destroyer. Their approach centers on analyzing the wakes left behind by ships, which produce distinct patterns on the sea surface akin to fingerprints.
In a peer-reviewed paper published in the Chinese journal Computer Simulation in April, Hong and his colleagues from the Navy Submarine Academy detailed the physical parameters necessary for accurate identification of U.S. warship models. “Using these parameters and the algorithm provided in the paper, it is possible to identify the target warship model under certain conditions,” the researchers noted.
Ship wakes can extend for tens of kilometers, providing crucial information even in blurry satellite photos. One significant challenge the team faced was extracting useful data amidst environmental noise, such as clouds and waves, which can obscure key features of a ship’s wake. While tracking naval vessels via satellite imagery is not new, the ability to do so using low-resolution images is relatively novel.
Existing methods typically rely on high-resolution imagery, but China’s new technique leverages publicly available, lower-quality images, potentially democratizing access to naval surveillance capabilities. Despite its innovative nature, the method has limitations, particularly with real-time imagery and target speeds exceeding 20 knots (23 mph, 37 kph).
China, like the U.S., has a sophisticated network of Earth observation satellites capable of high-resolution monitoring. However, this new technique could be particularly useful for nations with less advanced satellite capabilities. The researchers highlighted the need for further testing and refinement with more data to enhance the method’s reliability under varying sea conditions.