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Around the World in 80 Hours (Posted on 2024-07-30) Difficulty: 3 of 5
Phileas Fogg III wants to commemorate his grandfather's circumnavigation by going around the world in 80 hours. This will be by airplane, and he wants to start out at 16° South, travel somwhat north of east maintaining a constant direction bearing, and end up at the same longitude at latitude 41° North. This sort of path (constant direction bearing) is called a loxodrome, which maps as a straight line on a Mercator projection.

What should that constant direction bearing be?

  Submitted by Charlie    
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Solution: (Hide)
A loxodrome maps as a straight line on a Mercator projection map, which does also show true bearing, and Wikipedia tells us that (using a scale of unity) the y coordinate of a given latitude is

ln(sec(φ)+tan(φ))

where φ is the latitude.

As we're using a scale = 1/1, the longitude difference of a circumnavigation is 2*pi. Starting longitude is arbitrary, so that can be mapped at x=0.

On the Mercator map, then, the coordinates are;

(0, -0.282954531434068) and (2*pi, 0.785862966544544)

Calculating the arctan of the slope:

>> atand((0.785862966544544 + 0.282954531434068)/(2*pi))
ans =
          9.65403640612811
 

>> degrees2dms(ans) ans = 9°39'14.531062"

Comments: ( You must be logged in to post comments.)
  Subject Author Date
Another possible solutionJer2024-07-31 08:34:41
re: Possible solutionCharlie2024-07-30 12:02:27
Some Thoughtsthinking ...Larry2024-07-30 10:46:29
SolutionPossible solutionJer2024-07-30 09:22:26
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