Monday, 30 March 2015

Countries near New Zealand

New Zealand has many advantages: proximity to India and China are not amongst them

People sometimes claim that New Zealand is close to China and India. For instance here.

Viewing the Earth through the lens of the Mercator projection, the way google maps does, this misconception is almost forgiveable. New Zealand is over there on the same side of the map as Asia, just further down. However, the Mercator projection is a distorted view of the world that grossly exaggerates distances toward the poles.

What area would you define as close on a global scale? I suggest that a generous definition of close is that two countries are close if they are on the same quarter of the Earth's surface, and that a country not even on the same half of the world would be very far away indeed. So are China and India close to New Zealand by this definition?

Imagine a circle drawn on the surface of the Earth. Its radius is represented on the Earth's surface by a geodesic: a line of constant direction that curves as it travels around the earth. A geodesic that stretches 1/4 of the way around the circumference of the Earth will, if rotated through 360 degrees, draw out a spherical cap that covers half the world. The perimeter of this cap will be a circle on a globe but its shape will be distorted on a projected map.

A geodesic that stretches 1/6th of the way around the world will, when rotated, draw a cap that covers 1/4 of the Earth's surface. The countries that are inside such a spherical cap, with Wellington as its centre, are labelled on the map below. Clearly China and India are not among them.

Click image for bigger version

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