Author Topic: Don't use the sun to navigate without taking account of the time of the year  (Read 1332 times)

Lyle Brotherton

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Tomorrow (21062014) at 10:51 GMT will be the Summer Solstice, our longest day in the Northern Hemisphere and think about it, it really brought home the danger of using the maxim ‘The Sun Rises in the East and Sets in the West’ to navigate without taking account for the time of the year, because there is a whopping 47 degrees difference between the Summer & Winter Solstice sun rising bearings.

The NOAA have a new page to calculate sunrise/sunset by location time and date which is much easier to use with your coordinates; both longitude and time zone are defined as positive to the west, instead of the international standard of positive to the east of the Prime Meridian. http://www.esrl.noaa.gov/gmd/grad/solcalc/sunrise.html

In Google Earth to display your coordinates in Degrees/Minutes/Seconds, select the Tools menu bar and under the Options tab Tick the second box down under Show Lat/Long

The Winter Solstice will be at 23:03 GMT this year.
« Last Edit: June 21, 2014, 06:47:12 AM by Lyle Brotherton »
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njneer

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Excellent cautionary advice, Lyle.  It might also be worthwhile to point out that Solar Noon does not vary so much, since at local noon the sun will be very close to South, so that a shadow will be cast to the North (or South in the Southern Hemisphere).  There is an old trick whereby you can point the hour hand of your watch at the sun, and find South halfway between there and 12:00 on the watch dial.

MoonMan

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But, if you are in a place that is an hour in advance of Zone Standard Time, allow for that, and also allow for the difference in Longitude between actual place & the longitude used for Standard Time. Plus Four minutes per degree of Longitude West, Less if East.,
Keeping Track of where Here is in relation to There.