Over the past 15 years, the world of global positioning and satellite-based global navigation has been evolving dramatically. The U.S. Global Positioning System (GPS) and the Russian GLONASS satellite system have been joined by the Chinese BeiDou system, the European Union’s Galileo system, Japan’s Quasi-Zenith Satellite System (QZSS), the Indian Regional Navigation Satellite System (IRNSS) and others. Stanford is at the forefront of using interoperable signals from these satellite constellations to perform navigational tasks in various environments.
The two projects below—Advanced RAIM and Navigation via Commercial LEO Satellites are examples of Stanford research in this area.
ARAIM (Advanced RAIM), employed in some receivers, provides fault detection and exclusion (FDE) by using a minimum of six satellites, not only to detect a possibly faulty satellite, but also to exclude that satellite from the navigation solution so that the navigation function can continue without interruption. The goal of ARAIM is to detect the presence of a positioning failure. Upon detection, proper fault exclusion determines and excludes the source of the failure (without necessarily identifying the individual source causing the problem), thereby allowing GNSSnavigation to continue without interruption. The use of satellites from multiple GNSS constellations or the use of SBAS satellites as additional ranging sources can improve the availability of RAIM and FDE.
Navigation Via Commercial LEO Satellites
The Global Positioning System (GPS) is a vital component of systems ranging from the power grid, to wireless communications and even landing aircraft. However, GPS does have its drawbacks: it is easy to jam and it is very expensive to both operate and maintain. The challenge is to both improve the resilience of GPS while decreasing the cost of this now essential infrastructure.
To solve this, we look towards the changing market of space. New players are coming with proposals to build constellations of hundreds and even thousands of satellites in low Earth orbit (LEO). Their aim is delivering Internet to the world by providing global broadband coverage. We focus on how such constellations could be leveraged to carry a hosted payload, allowing them to act as navigation satellites.