Current and Continuing GPS/PNT Research
A list of current/ongoing GPS Lab research projects appears below.
Each project blurb contains a small square graphic (photo/diagram/etc.) and a short description of the project.Click the More Information link or corresponding sub-menu item on the left submenu to view details about a project.
Satellite Based Augmentation Systems (SBAS), augments GNSS enabling planes to make precision approaches and landings. The Wide Area Augmentation System (WAAS), is the U.S. implementation of SBAS. SBAS combines core constellation satellites with Geo-stationary satellites and ground based reference stations to monitor satellite ranging errors. Satellite ranging errors include: ephemeris, clock, ionosphere, troposphere, multipath & receiver noise.
The Local Area Augmentation System (LAAS), now more commonly known as the Ground Based Augmentation System (GBAS), is an all-weather aircraft landing system based on real-time differential correction of the GPS signal. Local reference receivers
located around the airport send measurements to a nearby processing unit, which use these measurements to formulate differential corrections for the GPS satellites being tracked by the reference receivers.
Cyber Safety for Transportation
Tomorrow’s transportation systems will be much more automated. It’s likely to include: automatic vehicles that will descend from the air and populate our roadways (automatic driving assistance or ADAS), railways (positive train control, PTC) and waterways (ships without crews). Moreover, the sky will be filled with aircraft that carry no pilots to mitigate flight risk. These will be drones or un-piloted air vehicles (UAVs). For efficiency, cars will drive while the enclosed humans snooze or send texts. Trains will slow or speed certain that they alone occupy the underlying track. Drones will fly confidently between building to monitor air pollution and crime in our major cities.
Securing tomorrow’s transportation system will involve many challenges. To address these challenges, SCPNT is sponsoring a number of research projects including Jamming Resistance, Anti-Spoofing, JAGER and Alternative PNT.
Time & Time Transfer
Currently, microwave time transfer systems between ground and space reach a level of precision of the order of the nanosecond (about 1 to 30 ns achieved with the GPS). An integration on ~ 30 days would be necessary to reach the 10-15 level. That cannot support the performance requirements and goals of the future optical atomic clock in space missions (such as ESA-SOC) which aim 10-17 level or better.
IMU Development & Testing
An inertial measurement unit (IMU) is an electronic device that measures and reports a body's specific force,angular rate, and sometimes the magnetic field surrounding the body, using a combination of accelerometers and gyroscopes, and sometimes, magnetometers. IMUs are typically used to maneuver aircraft,including UAVs, and spacecraft, including satellites and landers. Recent developments allow for the production of IMU-enabled GPS devices. An IMU allows a GPS receiver to work when GPS-signals are unavailable, such as in tunnels, inside buildings, or when electronic interference is present.
Over the lifetime of SCPNT, 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.
Marine Animals Tracking
Stanford’s Hopkins Marine Station, led by Professor Barbara Block, has been pioneering the use of GPS tags to study the migratory behavior of large marine animals—especially tuna, sharks whales and turtles. The GPS Lab and SCPNT have recently teamed with Hopkins Marine to develop a GPS tag that can provide a marine animal’s GPS position location in near real-time. The tag, when activated, transmits the animal’s position using satellite phone (satphone)technology. The tag is being developed to detect illegal shark fishing. It could also have other similar applications.
Positive Train Control
Positive train control (PTC) is a system of functional requirements for monitoring and controlling train movements as an attempt to provide increased safety. GPS and other GNSS Systems may be deployed as a reliable and continuous positioning system, suitable for train control. Stanford has been performing research in this area, with techniques similar to those used with WAAS certification. These research techniques include the development of software code to model rail safety issues caused by Multipath and the Ionosphere.
GNSS Software Receiver
A GNSS software receiver is an implementation that has been designed and implemented following the philosophy of Software-defined radio. This is done using a reconfigurable computational platform such as a microprocessor, digital signal processing element, graphic processor, or field programmable gate array. This is in contrast with a traditional GNSS receiver implementation, which leverages a hardwired application specific integrated circuit (ASIC). The software receiver provides maximum flexibility, the ability to redesign the architecture quickly and efficiently, allowing candidate signal processing algorithms to be designed and assessed.