WGS84 and Web Mercator

What is mocato projection?

Mercator projection, also known as "equisigned positive axis cylindrical projection", was developed in 1569 by the Dutch cartography house Mercator, assuming that the Earth is enclosed in a hollow cylindrical
And then imagine that there is a lamp in the center of the earth, and the graphics on the sphere are projected onto the cylinder, and then the cylinder is expanded, this is a mocato projection with a standard weft at zero (I .e., the Equator ).
A map of the world. There is a conversion formula from the ball to the plane, which is not listed here.
Google
Why do we choose mocato projection?

The "equal angle" feature of mocato projection ensures that the shape of an object remains unchanged. After a square object is projected, it will not become a rectangle. "Angular" also ensures the correctness of the direction and position of each other. Therefore, it is often used in navigation and air, while Google does not make errors when calculating the direction of people to query the ground features.
The "cylindrical" feature of mocato projection ensures that both the North and South (weft) and the East and West (meridian) are parallel straight lines and perpendicular to each other. In addition, the longitude line interval is the same, and the weft line interval increases gradually from the standard weft line (here it is the equator, or other weft lines) to two levels.
However, "Angular" inevitably results in huge deformation of the area, especially in the bipolar area. Obviously, Greenland is N times larger than the actual area. However, it doesn't matter if you have more detailed information about the comrades who are exploring the polar region or taking the exams.

 

 

Why is it a Circular Sphere instead of an elliptical sphere?

This is simple because it is easy to implement and easy to calculate. The accuracy is less than 0.33% in theory, especially when the scale is larger and the terrain is more detailed.
Web
Mocato projection Coordinate System
:
Take the whole world, the Equator as the standard weft, the primary meridian as the central meridian, the intersection of the two is the coordinate origin, east to north is positive, and west to south is negative.
X axis: Because the equator radius is 6378137 meters, the Equator perimeter is 2 * PI * r = 2*20037508.3427892. Therefore, the value range of the X axis is [-20037508.3427892, 20037508.3427892].
Y axis: It can be seen from the mocato projection formula, but also has a signal, when the latitude Phi is close to the pole, that is, 90 °, the y value tends to be infinite. These "lazy engineers" set the value range of the Y axis to [-20037508.3427892, 20037508.3427892] to a square.

 

Corresponding geographic coordinate system
:

The projection coordinate system (PROJCS) is a plane coordinate system, in meters.
The geographical coordinate system (GEOGCS) is an elliptical coordinate system, measured in longitude and latitude. Longitude: No problem. The global range is recommended: [-180,180].
Latitude: It is known above that the latitude cannot reach 90 °. The Lazy gets-20037508.3427892 for the square. After Inverse calculation, the latitude is obtained.
85.05112877980659. Therefore, the latitude value range is [-85.05112877980659, 85.05112877980659]. What about other regions?
? It's okay. You don't care.
Therefore, the range of the geographic coordinate system (longitude and latitude) is: Minimum (-180,-85.05112877980659), maximum (180, 85.05112877980659)