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Old 18th Sep 2014, 22:16
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Straighten Up
 
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Gen Nav Mercator Projections

I'm working through a ProPilot workbook so I can't check my answer to this (as they aren't provided) but just wanted to check I'm going about it the right way

The total length of the 53N parallel of latitude on a direct Mercator chart is 133cm. What is the approximate scale of the chart at latitude 30S.

My working:

Circumference of earth at 53N = Pi(12732*cos53) = 7662km
Scale at 53N = 1 over 766,200,000/133 = 1/5,760,902
Scale at 30S = cos30/cos53 * 5,760,902 = 1/8,229,860

Can anyone confirm if I've done this correctly?

Thanks.
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