It’s towel day.
Daily Archives: May 25, 2010
Never the Twain Shall Meet
Never, in this case, is 100 years.
After keeping us waiting for a century, Mark Twain will finally reveal all
The creator of Tom Sawyer, Huckleberry Finn and some of the most frequently misquoted catchphrases in the English language left behind 5,000 unedited pages of memoirs when he died in 1910, together with handwritten notes saying that he did not want them to hit bookshops for at least a century.
That milestone has now been reached, and in November the University of California, Berkeley, where the manuscript is in a vault, will release the first volume of Mark Twain’s autobiography.
OK, what gets me is not that Samuel Clemens aka Mark Twain, did not want his autobiography released until 100 years after his death. What gets me is that he died April 21, 1910, and the first edition won’t be out until November of 2010. What? Not enough lead-time to get the project done?
GPS, New and Improved
GPS is getting an $8-billion upgrade
[S]cientists and engineers — including those at a sprawling satellite-making factory in El Segundo — are developing an $8-billion GPS upgrade that will make the system more reliable, more widespread and much more accurate.
The new system is designed to pinpoint someone’s location within an arm’s length, compared with a margin of error of 20 feet or more today. With that kind of precision, a GPS-enabled mobile phone could guide you right to the front steps of Starbucks, rather than somewhere on the block.
The story mentions that a predecessor of GPS was Transit, to support Polaris submarines. I went to a talk recently which mentioned other programs as well: there was SECOR (SEquential COllation of Range), 621B and TIMATION. I found a brief history of these programs. The military was testing various strategies for geolocation, and each had its strengths and weaknesses. You could have the satellites be autonomous or rely on ground stations; autonomous satellites need good space-qualified clocks, which were tough to come by in the 60s, but if ground station was lost, the whole system would go down. Orbital altitude was another variable — geostationary satellites had poor coverage at high latitudes, but you required more satellites as you got into lower orbits, with progressively shorter observation windows. (A low-earth orbit (LEO), like the ISS, would require of order 100 satellites for good coverage) And various communication strategies could be employed.
They were able to draw on the experiences of each program and come up with a system that seems to have worked out pretty well.