On 4/19/2013 6:36 PM, Yigit Turgut wrote: > Hey Bob, > > Try atomic clocks, they are precise and independent of gps. > Actually, I have, but I plan to sell these trackers worldwide, and WWVB=20 has distance limitations. It does OK in northern South America, but won't reach=20 further down. Europe is covered va Swiss, German and UK time servers. Anybody know their=20 range of coverage? --BA > YT > > > On Sat, Apr 20, 2013 at 1:11 AM, Bob Axtell wrote: > >> My need is precision time, nothing else. Before GPS, ships navigated >> knowing the time >> and the sun angle. I know where I am at, so with a precise clock, I can >> obtain the sun angle. >> >> It seems to me that there would be little reason to shut the time >> service off, which only needsONE >> bird. >> >> --Bob A >> >> On 4/19/2013 7:27 AM, RussellMc wrote: >>>> This came up in a conversation related to solar tracking. Will the >>>> military shut off >>>> ALL of the GPS services, or just positioning, during a wartime footing= ? >>>> >>>> How about time/date services? >>> First casualty is to change to "selective availability" >>> Accuracy drops substantially. >>> This was the mode the system ran in fr many years when first introduced= .. >>> AFAIR this was done for 'Desert Storm'. >>> >>> I do not know if it is done, but you could shut it down regionally so >>> that a portion of the globe was without service. How small and well >>> defined you could do this would be "interesting". >>> A very determined person could gain useful information from two >>> satellites and possibly from one. >>> >>> Russia operates a GPS system (GLONASS*) that (memory says) uses polar >>> elliptical orbit satellites as in that orbit shape they are in the >>> high poleward part of their orbit for the majority of the time. >>> Usefulness diminishes as you go southward. If they transmit around the >>> whole orbit you MAY get some use from low altitude satellites in the >>> southern hemisphere. >>> >>> >>> >>> Russia >>> >>> ___________________ >>> >>> http://en.wikipedia.org/wiki/Satellite_navigation >>> >>> http://en.wikipedia.org/wiki/Global_Positioning_System >>> >>> Says: >>> >>> Initially, the highest quality signal was reserved for >>> military use, and the signal available for civilian use was >>> intentionally degraded (Selective Availability). This changed with >>> President Bill Clinton ordering Selective Availability to be turned >>> off at midnight May 1, 2000, improving the precision of civilian GPS >>> from 100 meters (330 ft) to 20 meters (66 ft). The executive order >>> signed in 1996 to turn off Selective Availability in 2000 was proposed >>> by the U.S. Secretary of Defense, William Perry, because of the >>> widespread growth of differential GPS services to improve civilian >>> accuracy and eliminate the U.S. military advantage. Moreover, the U.S. >>> military was actively developing technologies to deny GPS service to >>> potential adversaries on a regional basis.[18] >>> >>> __________________ >>> >>> GLONASS >>> >>> http://en.wikipedia.org/wiki/GLONASS >>> >>> iPhone 4S, iPad Mini and HTC provide GPS & GLONASS capabilit= y. >>> >>> GPS and phone baseband chips from ST-Ericsson, Broadcom and >>> Qualcomm support GLONASS in combination with GPS. >> >> -- >> >> The only place success comes before work is in the dictionary. >> >> VINCE LOMBARDI >> >> -- >> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> --=20 The only place success comes before work is in the dictionary. VINCE LOMBARDI --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .