The way I understand the geolocation device is that dawn rises at the same time along different longitudes. If you know what time sunrise is and how long the day is on a particular day you know your latitude as well as your longitude.
On a deserted island, the time of sunrise is the number of hours before high solar noon....and maybe half way between sunrise and sunset. This manual seems to indicate these concepts: http://www.wildlifecomputers.com/Downloads/Documentation/WC-GPE%20Suite%20Manual.pdf It's because of the tilt of the earth? Roger W. Sinnott wrote: > Brent, > > I think you could determine your latitude this way, but not your longitude. > For the longitude, you would need some way to relate your local sunrises and > sunsets to the local time at some known longitude, such as that of > Greenwich. > > In other words, the geolocation tagging gadget must carry a time-of-day > clock from a known longitude. This is the same as the age-old longitude > problem that all mariners faced. > > -- Roger > > > ----- Original Message ----- > From: "Brent" <bren...@verizon.net> > To: "Sundial List" <sund...@rrz.uni-koeln.de> > Sent: Tuesday, October 12, 2010 5:05 PM > Subject: Re: Light Based Geolocation > > > >>So I am marooned on a island with nothing but I might be able to >>determine a few things that I could write on a message in a bottle >>that would help my rescuers determine my exact location. >> >>By careful sunrise observation I could determine the solstices. >>Now I have a calendar. >> >>I know dawn to dawn is 24 hours so I could make a clock with a washed >>up bottle filled with sand and measure/mark what comes out in one day. >> >>Then I could cut that sand in half for 12 hours and half again for 6 >>hours and half again for 3 hours and then thirds for one hour. >>Now I have an hour clock. >> >>Now I can measure the hours of daylight from dawn to dusk on the >>solstice and send that in the bottle and my rescuers will be able to >>determine my latitude and longitude. >> >>Of course I would have to say northern or southern solstice but that's >>easy because we know the sun rises in the east. >> >>Would this be enough information? >> >>thanks again; >>brent >> >>--------------------------------------------------- >>https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> > > > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
