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Distances of longitude?

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As you may already know the meridians of longitude converge towards the poles, so therefore there is no set scale. The equation your after is:Departure (Distance longitude, nm) = Change in Longitude x CosLattitudeThen if you wanted to work out the reverse, i.e change in longitude, you use the Secant of Lattitude:Change in Longitude = Departure x 1/Cost Lattitude1/Cost Lattitude = Secant of LattitudeUltimatley:Change in Longitude = Departure x Secant LattitudeThanks.Cheersobklogo.gif[/img][/font]

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Forgot to point out, Change of longitude is in Minutes.Cheers[br]obklogo.gif[/img]

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obk is right. Cosine of latitude is the factor here. So, for example, at 60 deg latitude (cos 60 = 0.5) 1 deg will be equal 30 nm.Michael J.

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EGADS! I'm having flashbacks to Miss Campbell's 12th grade trig class (which I failed). Could that have been 1957? When calculators were made of wood? And new math hadn't been invented? And the acronym "PC" meant neither personal computer nor politically correct? And I dreamed of owning a '57 Chevy as I cruised around proudly in my '50 Ford with dual exhausts and hardly any muffers at all?My life is flashing before my eye, is the end near . . . ? R-

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Hi someone.There are formulas that are used to calculate distances between two points on the surface of the earth. Uses a lot of trig. I made an EXCELL spreadsheet that does the math for you. All you have to do is enter the latitude, longitude and elevation and it spits out the distance between the points. I

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Almost right :-). It was 1958. And the car was a '51 Mercury with lakes pipes and spun moons. And my best friend had the '57 Chevy. And I didn't fail Trig - I got a solid D. And the end is, indeed, much nearer.....sigh....Doug

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