How to enable the concept of scaling level in IOS map development

When developing the map app, we found that the SDK did not set the map zoom level. To display the map, we set its center point and then use a span to control the display area, you will ask, what is span? In fact, it is also related to latitude and longpolling. If there is a concept of scaling level, it is easier to understand during development. I collected the relevant information, which gave mkmapview the concept of scaling level.

Source code: http://troybrant.net/blog/2010/01/set-the-zoom-level-of-an-mkmapview/

Proof of mathematics: http://troybrant.net/blog/2010/01/mkmapview-and-zoom-levels-a-visual-guide/

It doesn't matter if you don't understand the mathematical principles he said. You can use the source code directly. Well, if you don't see his license statement, change your name.