AbstractGlobal Navigation Satellite Systems (GNSS) are satellite constellations that generate signals that can be received virtually anywhere, anytime, and in any weather anywhere in the world. The article discusses the systems that are fully active and those that are still being developed. The systems are intended to be independent, complementary, and interoperable. Most future aviation users are likely to rely on multi‐constellation receivers, i.e., receive and process the GNSS signals to complement and enhance each other. The general description of how the systems work concludes with some of the remaining challenges. WIREs Comp Stat 2011 3 383–384 DOI: 10.1002/wics.158This article is categorized under: Applications of Computational Statistics > Signal and Image Processing and Coding