NavList:

Thanks, Geoffrey, for the very interesting and informative summaries. With regard to:

" A lively debate ensued during the question period after the talk. If Stephens was correct, why was the public allowed access to the GPS system? Any right thinking government would not have allowed potential enemies of the US to have wide open access to a guidance system of such accuracy right from the get-go. A satisfactory answer to this question did not emerge, and it seems that many experts in the audience had been asking this question for many years and have never got a satisfactory answer. However, many experts in the audience also recounted how GPS had been 'mucked about with' and and even turned off at key moments during the Gulf Wars and the campaign in Afghanistan, so justifying the Europeans launching the Galileo constellation at enormous expense, with the Russians, Chinese, Indians and Japanese also putting up their own systems."

1) GPS has never been turned off.
2) GPS was designed to be used by both the military and the civil community from the get-go. Please see the first few paragraphs of the intro to my Innovation column in the April issue of GPS World:
http://gpsworld.com/innovation-ground-based-augmentation/
We (academics) used GPS even before the Reagan Administration's 1983 announcement and we even had unfettered access to the P-code throughout the 1980s.

Richard Easton's recent GPS Declassified: From Smart Bombs to Smartphones is a trustworthy source for the details on GPS evolution.

-- (Prof.) Richard Langley
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