GNSS System
True Story of GPS Yet to Be Told
April 7, 2010Invention Claims Inaccurate
The recent induction of an individual into the Inventor’s Hall of Fame was based on inaccurate claims of involvement in, and origination of, the concept of GPS. The May 2010 issue of GPS World will carry a complete and authenticated story of the system’s development, authored by the original director of the U.S. Air Force Joint Program Office, and vetted by every significant engineer and manager still living who was involved with the building of GPS. The article gives the true history of the system and bestows credit where credit is due.
The article establishes that:
- The Air Force 621B program performed a secret system study in 1964/66 (declassified in 1979) that examined all alternative passive ranging systems. It pointed out that the Easton method was much less desirable than the four-satellite positioning concept actually adopted for GPS. The authors of that study, Woodford and Nakamura of the Aerospace Corporation, deserve the credit for being the first describers of the GPS technique. This study predated the Easton patent application by four years.
- While both the Air Force and the Naval Research Laboratory (NRL) advocated atomic clocks in space, NRL demonstrated no space-hardened clock before the first GPS launches. Instead, Rockwell Corporation, under U.S. Air Force direction, developed the first space-qualified clocks. Only USAF/Rockwell clocks were operational aboard the first four GPS satellites; this constituted an essential key in gaining approval at a 1980 meeting of the Defense Systems Acquisition Review Council to proceed with full-scale GPS development.
- An attentive reading of the 1974 Easton patent shows that the Easton signal was not the code-division multiple-access (CDMA) signal adopted for GPS, and was self-jamming and not resistant to interference; the Easton method required an atomic clock at the user, contrary to GPS methodology established earlier and in use up to the present day; the Easton method was two-dimensional, and would have led to self-interference if three-dimensonal positioning were attempted. Thus the Timation proposal documented by Easton was neither GPS nor was it a prototype for GPS. Further, the technique had been studied by the Air Force four years before Easton filed his patent.
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Comments
on: April 14, 2010 - 7:11am
Be careful with the claims for this story. A "true history" should be subject to criticism by professional historians who would handle personal testimony with care -- it is subject to bias. Most good history is based on documentation. Personal history -- diaries, journals, interviews, autobiographies, etc. are handy, but should be an augmentation to solid documentation.
Some historians might also label your "true history" as "celebratory history": It seeks to emboss and enhance reputations and personal successes without a balanced appraisal of mistakes and lost opportunities.
I look forward to reading the article.