How are these longitude and latitude lines determined? The earth is constantly rotating around the earth axis (the earth axis is an imaginary line passing through the north and south poles of the earth and the center of the earth). Draw a great circle perpendicular to the earth axis in the middle of the earth, so that every point on the circle is equal to the distance between the north and south poles. This circle is called the equator. On the north and south sides of the equator, many circles parallel to the equator are drawn, which is the "weft circle"; The line segments that make up these circles are called parallels. It is defined as the angle between the line from a point on the earth's surface to the center of the sphere and the equatorial plane. We set the equator as zero latitude, 90 degrees south latitude to north, south latitude to south, and north latitude to north. The North Pole is 90 degrees north latitude and the South Pole is 90 degrees south latitude. Latitude also marks the hot and cold climate, for example, there is no winter in equatorial and low latitudes, no summer in polar and high latitudes, and four distinct seasons in middle latitudes.

bend

Secondly, from the North Pole to the South Pole, you can draw many great circles whose north-south direction is perpendicular to the equator of the earth, which are called "meridian circle"; The line segments that make up these circles are called meridians. AD 1884

Plane coordinate diagram

In 2000, it was internationally stipulated that the longitude line passing through Greenwich Observatory in the suburb of London, England, was taken as the starting point of longitude calculation, that is, the longitude of 0.000 minutes and 0 seconds, also known as the "prime meridian". Its east is east longitude, *** 180 degrees; It is west longitude, *** 180 degrees. Because the earth is round, the longitude of east longitude 180 degrees and the longitude of west longitude 180 degrees are the same longitude. Countries have designated longitude 180 degrees as "international international date line". In order to avoid using two different dates in the same area, international date line will be slightly biased when it comes to land.