James J. Spilker, Jr.


James J. Spilker, Jr.
Fields of study
IEEE Edison Medal


As one of the principal designers and analysts of the Global Positioning System (GPS), James J. Spilker Jr.’s contributions to GPS development have truly benefited billions of people around the world. The satellite-based navigation system has become an integral part of society through mobile phones and other portable devices that rely on GPS timing, commercial and private aviation, sea navigation, geolocating personal vehicles, and providing disaster warning and recovery support. Dr. Spilker developed the initial technologies to enable successful GPS operation, and he has continued to provide innovations important to the further growth of the GPS. Dr. Spilker designed the L1 C/A code during the 1970s, which became the GPS civilian signal now used by 2 billion people worldwide. His delay lock loop process for tracking code division multiple access (CDMA) signals is essential to GPS accuracy. He has since helped develop the new L5 civilian signal, first launched in 2011, which provides higher accuracy and more resistance to the effects of interference, such as space weather, on navigation. Dr. Spilker also co-invented the split spectrum mode (now called binary offset carrier, or BOC) for modern GPS ranging that will allow civilian and military signals to use separate areas of the spectrum. He also developed adaptive vector tracking for simultaneously tracking ranging signals from multiple satellites while maintaining accuracy and improving performance against interference. Vector tracking will be critical to handling GPS satellite navigation expansion as new GPS satellites and signals are introduced by agencies around the world. Dr. Spilker’s highly cited book Global Positioning System: Theory and Applications (American Institute of Aeronautics and Astronautics, 1996) is considered the standard reference for the GPS and won the AIAA Sommerfield Book Award. His popular textbook Digital Communications by Satellite (Prentice-Hall, 1977) went through ten printings.

In 2015, Spilker received the IEEE Edison Medal for a career of meritorious achievement. In addition, he is an IEEE Life Fellow and member of the U.S. National Academy of Engineering. Currently, Dr. Spilker is currently executive chairman of AOSense Inc., Sunnyvale, CA, USA and Professor (Consulting), Stanford University, Stanford, California.