Every point on the earth actually has a two-dimensional coordinate

Similar to rectangular coordinates in mathematics

The abscissa is latitude.

The ordinate is longitude.

In this way, latitude and longitude can be combined to determine a position.

Then draw each latitude and longitude with a straight line.

Just like drawing paper.

It looks like a net.

That is, latitude and longitude net

Latitude is divided into north latitude and south latitude.

The dividing line is a parallel line of 0.

Which is what we call the equator.

The abscissa of the range from the equator to the North Pole becomes the north latitude.

On the contrary, it is south latitude.

This is easy to understand.

Longitude is even more difficult.

Longitude Longitude is 0 degrees.

That is, the prime meridian in the book (passing through London, England)

I won't go into details here.

Because the earth is spherical.

So this 0 degree meridian is actually a circle.

The center of this circle coincides with the center of the earth.

Then the earth axis divides the circle into two semicircles (imagine? )

There must be a difference from the prime meridian to the other side.

This makes the difference between east longitude and west longitude.

We know that China is in the Eastern Hemisphere.

America is in the western hemisphere.

Then the ordinate on the eastern hemisphere is the east longitude.

On the contrary, it is a western classic.

East longitude and west longitude both have a 180 degree.

But in the end, it merged into a line.

This is the other side of the cycle I mentioned earlier.

I don't know if I can understand this.

I don't understand. Add me and I'll elaborate.