Perhaps the little sketch attached will help. On the surface of the earth there is a circle of locations that see the sun at the same elevation at any time. These circles of constant elevation are circular lines of position. At a different time there is a new circular line of position for the new solar altitude. Your position is fixed where these two circles cross. There are usually two solutions. One can be discarded as you know approximately where you are. This is the fix determined by sundial technology in the TV show.
It sounds simple to solve two equations, with two unknowns. With complex trig expressions it is not so straight forward. Sara S. mentioned the normal method of solving by using an assumed position and calculating how far off your assumption was. You do this for both lines of position, calculating the distance and direction to the line. After reducing the data with tables or computers, the navigator generally then plots his fix, the intersection of the lines of position from the assumed position. Computers now do this with iterative calculations without manual plotting but this is not seen or appreciated by the user. GPS works the same way using time signals from different satellites. Here the lines of position are hyperbolic rather that circular, but the principles are the same. My interest in sundials started with an interest in celestial navigation so I have come full circle. Regards, Roger Bailey Walking Shadow Designs N 40.6 W 123.4 -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of wee-meng lee Sent: February 14, 2006 5:12 PM To: sundial@uni-koeln.de Subject: Re: Numb3rs I too don't get it. Does anyone have a spreadsheet that computes a position from what was discussed below? thx weemeng -
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