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Early GPS Lab Research

The 1990’s and early 2000’s were an extremely productive period for innovative GPS research at Stanford. The landmark Gravity Probe B Mission (GP-B) that ran from 1963-2011 pioneered the use of GPS technology for precision spacecraft attitude and translation control. Many spinoff uses of GPS technology pertaining to aircraft, emerged from GP-B, including:

  • Autonomous Aircraft Control
  • Airplane Navigation—Takeoffs and Landings
  • Enhanced guidance & situational awareness for aircraft

View  Paper showing Stanford doctoral student leadership in GPS research: Professional Publishing Trends of Recent GPS Doctoral Students by Leo Mallette, ION Conference Presentation, 2006.

Below is a list of early Stanford GPS Lab research projects. Click the More Information link or corresponding sub-menu item to the left to view details about a project.

Autonomous Aircraft

Stanford demonstrated the first non-military GPS guided autonomous aircraft (or UAV) circa 1996. Commercial, non-military GPS-guided UAVs (or drones) have become commonplace for use by commercial companies and/or hobbyists.

GPS for Airplane Navigation, Takeoffs and Landings

A commercial GPS Receiver and multiple antennas were mounted on a small Cessna airplane to perform local flight tests near Stanford in the early 1990’s. The tests showed that GPS could provide aviation attitude control for en route and precision approaches at the Palo Alto airport. The tests were broadened to include local terrestrial pseudolites transmitting a GPS signal, which allowed for successful automatic landing of the Cessna.

RAIM

Receiver autonomous integrity monitoring (RAIM) is a technology developed to assess the integrity of GPS signals in a GPS receiver system. It is of special importance in safety-critical GPS applications, such as in aviation or marine navigation. RAIM detects faults with redundant GPS pseudorange measurements. That is, when more satellites are available than needed to produce a position fix, the extra pseudoranges should all be consistent with the computed position. A pseudorange that differs significantly from the expected value (i.e., an outlier) may indicate a fault of the associated satellite or another signal integrity problem (e.g., ionospheric dispersion).

JPALS

Receiver autonomous integrity monitoring (RAIM) is a technology developed to assess the integrity of GPS signals in a GPS receiver system. It is of special importance in safety-critical GPS applications, such as in aviation or marine navigation.  RAIM detects faults with redundant GPS pseudorange measurements. That is, when more satellites are available than needed to produce a position fix, the extra pseudoranges should all be consistent with the computed position. A pseudorange that differs significantly from the expected value (i.e., an outlier) may indicate a fault of the associated satellite or another signal integrity problem (e.g., ionospheric dispersion).

LORAN/eLORAN

eLoran is a low frequency terrestrial navigation system based on a number of transmission stations, which emit precisely timed and shaped radio pulses centred at 100 kHz radio frequency. LORAN, short for LOng-RAnge Navigation, was a hyperbolic radio navigation system developed in the United States during World War II. It was first used for ship convoys crossing the Atlantic Ocean, and then by long-range patrol aircraft. The US Navy began development of Loran-B, which offered accuracy on the order of a few tens of feet, but ran into significant technical problems. The US Air Force had worked on a different concept, which the Navy picked up as Loran-C. Loran-C offered longer range than LORAN and accuracy of hundreds of feet. The US Coast Guard took over operations of both systems in 1958.

GPS Tunnel in the Sky

Three-dimensional flight displays can increase the efficiency of remote sensing flight operations by providing enhanced guidance and situational awareness on straight and curved flight paths. Such a display depicts an “out-the-window” perspective view of the world along with a tunnel through which the pilot flies the aircraft. Using differential GPS, inexpensive graphics hardware, and a flat-panel display, a prototype  system was built and flight tested to demonstrate significant advantages over conventional instruments.