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</o:shapelayout></xml><![endif]--></head><body bgcolor=white lang=EN-CA link=blue vlink=purple style='WORD-WRAP: break-word;-webkit-nbsp-mode: space;-webkit-line-break: after-white-space'><div class=WordSection1><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:blue'>Larry,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:blue'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:blue'>Just so you know that it is possible… some of the newer GPS units on the market today are capable of automatically determining the local time zone.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:blue'>This is achieved with proprietary time zone maps that are installed inside the GPS at the factory.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:blue'>Newer versions of the maps are bundled inside firmware images so that you automatically get the latest map when you upgrade the firmware on your GPS.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:blue'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:blue'>If these built in time zone maps are not accurate (or if you find yourself in an area with disputed time zones), it is possible to turn off automatic mode and then manually enter the time zone of your choosing.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:blue'> <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:blue'>A Google search reveals that one of the GPS manufacturers stores its time zone data in a file that is approximately 600kB.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:blue'>I think we can assume that the data in this file is written in a very heavily compressed format; it could theoretically be many megabytes if uncompressed.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:blue'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:blue'>-chris<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:blue'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'><p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> Larry Ober [mailto:larry.ober@att.net] <br><b>Sent:</b> February 3, 2011 2:27 PM<br><b>To:</b> tz@lecserver.nci.nih.gov<br><b>Subject:</b> Re: lat/lon to time offset database<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Hi John,</span><o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Well there would be some level of accuracy question. The more accurate the polygon the larger the database. Also if the lat/lon data was provided by GPS, there is the question of signal availability.</span><o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Basically it just seems dumb that I need to tell my GPS what time zone it's in. LOL</span><o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Best Regards</span><o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Larry</span><o:p></o:p></p></div><blockquote style='border:none;border-left:solid black 1.5pt;padding:0cm 0cm 0cm 4.0pt;margin-left:3.75pt;margin-top:5.0pt;margin-right:0cm;margin-bottom:5.0pt'><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>----- Original Message ----- <o:p></o:p></span></p></div><div><p class=MsoNormal style='background:#E4E4E4'><b><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>From:</span></b><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'> <a href="mailto:john.haxby@oracle.com" title="john.haxby@oracle.com">John Haxby</a> <o:p></o:p></span></p></div><div><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>To:</span></b><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'> <a href="mailto:tz@lecserver.nci.nih.gov" title="tz@lecserver.nci.nih.gov">tz@lecserver.nci.nih.gov</a> <o:p></o:p></span></p></div><div><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Sent:</span></b><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'> Thursday, February 03, 2011 1:54 PM<o:p></o:p></span></p></div><div><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Subject:</span></b><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'> Re: lat/lon to time offset database<o:p></o:p></span></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><p class=MsoNormal><o:p> </o:p></p><div><div><p class=MsoNormal>On 3 Feb 2011, at 18:33, Larry Ober wrote:<o:p></o:p></p></div><p class=MsoNormal><br><br><o:p></o:p></p><p class=MsoNormal><span class=apple-style-span><span style='font-size:13.5pt;font-family:"Courier New"'>I am looking at building a small embedded system (No OS) that will require</span></span><span class=apple-converted-space><span style='font-size:13.5pt;font-family:"Courier New"'> </span></span><span style='font-size:13.5pt;font-family:"Courier New"'><br><span class=apple-style-span>determining the local time from the lat/lon of a location. So basically I need</span><span class=apple-converted-space> </span><br><span class=apple-style-span>lat/lon to time offset from "GMT".</span></span><o:p></o:p></p></div><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal>Does that work? I'm sure I can find places in Spain that are that are close to Lisbon than they are Madrid but being in Spain the timezone should be Europe/Madrid. Also, when you're on going through the channel tunnel do you go from being closer to Paris than you are to London only when you've left Calais? Or before you get to Dover?<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>Or have I got hold of the wrong end of the stick?<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>jch<o:p></o:p></p></div></blockquote></div></body></html>