Imagine you are standing on a street in the center of Annapolis, Md., and someone asks you how far it is to the equator. Use the size of the Earth and your position in terms of latitude and longitude to figure it out.
Tools for Calculating the Distance
A meter is defined as one 10-millionth of the distance from the equator to the North Pole. This means the distance from the equator to the North Pole is 10 million meters, or 10,000 kilometers. One kilometer = 0.6214 miles, so 10,000 kilometers = 6213.7 miles. The circumference of the Earth is four times that, or 24,854.8 miles. The latitude at the equator is zero degrees, while the latitude at the North Pole is 90 degrees. That means that each degree of latitude equates to 10,000 divided by 90, which is 111.111 kilometers or about 69 miles.
Method of Approximation
If you know that the latitude of the spot where you are standing -- Annapolis, Md., in this case -- is 38.978 degrees north, then the distance to the equator is 38.98 X 111.111, or 4331 kilometers, which means that Annapolis is 2691 miles from the equator. In general, then, to determine the distance from any location to the equator, calculate the latitude in decimal degrees X 111.111, and convert kilometers to miles by multiplying the number of kilometers by 0.6214. This calculation is a close approximation, because the Earth is not a perfect sphere but is “flattened” at the top and bottom due to its spin.