Study tiles in Google Map

I. mocato projection
Google map uses epsg: 900913 standard mocato projection (geo-circular map projection)
Y = r * ln (TAN (PI/4 + A/2 ))
X = r * B
When Y is equal to PIR, the projection chart is just a square, and the latitude is 85.05113 degrees.

[-85.05113, 85.05113]. The maximum longitude is [-180,180]. The equator length is 6378137 meters, so the maximum edge of the family can be obtained according to the formula.

Boundary [-20037508.342789244, 20037508.342789244] meters.

Ii. tile pyramid
Google map is a tile made up of 256*256 images. At the initial level (0), the whole earth is projected on only one tile.

On-chip, that is, 256 pixels represent 40075016.685578488 meters. That is, 40075016.685578488/256 = 156543.033928041 (

Meters/pixels ).
The scale-in is implemented by the quadtree, that is, after one level is enlarged, the original image is split into four. See

Iii. tile URL
Shape:
Http://mt0.google.cn/vt/lyrs=m@180000000&hl=zh-CN&gl=cn&src=app&x=3&y=1&z=2&s=Ga
Mt0: Server Name (Google map has four servers)
Hl: Language
X: ID of the X axis of the tile
Y: ID of the Y axis of the tile.
Z: the zoom level of the tile.
S: "" and "Galileo" are 8 characters in total (meaningless)
Computing relationship:
Mt = (x + y) % 4
S = (3 * X + Y) % 8
Blank tile URL
Http://maps.gstatic.cn/intl/zh-CN_cn/mapfiles/transparent.png

Note: The tile information number starts from the upper left corner (0, 0.

 

Note: The idea comes from the network.

Share:

[-85.05113, 85.05113]. The maximum longitude is [-180,180]. The equator length is 6378137 meters, so the maximum edge of the family can be obtained according to the formula.

Boundary [-20037508.342789244, 20037508.342789244] meters.

Ii. tile pyramid
Google map is a tile made up of 256*256 images. At the initial level (0), the whole earth is projected on only one tile.

On-chip, that is, 256 pixels represent 40075016.685578488 meters. That is, 40075016.685578488/256 = 156543.033928041 (

Meters/pixels ).
The scale-in is implemented by the quadtree, that is, after one level is enlarged, the original image is split into four. See

Iii. tile URL
Shape:
Http://mt0.google.cn/vt/lyrs=m@180000000&hl=zh-CN&gl=cn&src=app&x=3&y=1&z=2&s=Ga
Mt0: Server Name (Google map has four servers)
Hl: Language
X: ID of the X axis of the tile
Y: ID of the Y axis of the tile.
Z: the zoom level of the tile.
S: "" and "Galileo" are 8 characters in total (meaningless)
Computing relationship:
Mt = (x + y) % 4
S = (3 * X + Y) % 8
Blank tile URL
Http://maps.gstatic.cn/intl/zh-CN_cn/mapfiles/transparent.png

Note: The tile information number starts from the upper left corner (0, 0.

 

Note: The idea comes from the network.