thumb|Chayka pulse
Chayka (, lit. "gull") also known as ''Radiotekhnicheskaya Sistema Dal'ney Navigatsii'' abbreviated as RSDN (lit. Radio-technology System for Distant Navigation) is a Russian terrestrial radio navigation system, similar to Loran-C. It operates on similar frequencies around 100 kHz, and uses the same techniques of comparing both the envelope and the signal phase to accurately determine location. The systems differ primarily in details.
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).