I don't know. I think trying to track the sun with PV panels based solely on time and date is a little suspect. As you've pointed out, you need a _very_ precise long term clock, but you also need angular position of the panel as well. How are you measuring that? What's it's repeatability and reliability and how well is it calibrated during install? I would think that some type of sensor that finds the brightest spot in the sky would be a more consistent solution. Granted there would be additional controls (reset for morning, limit hunting during cloudy days, etc) Possibly some combination - time based algorithm with the clock disciplined by a sun detection. Use a common crystal (~5min/yr) and limit the discipline to something on the order of a second or two per day. -Denny On Fri, Apr 19, 2013 at 3:11 PM, 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 capability= .. > > > > 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 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .