Each zoom level doubles in both dimensions, so a single tile is replaced by 4 tiles when zooming in. At the outer most zoom level, 0, the entire world can be rendered in a single map tile. Most tiled web maps follow certain Google Maps conventions: Tile(Point and Zoom) to Web Mercator Coordinatesīefore diving into the simple math of calculating the web mercator coordinates, we need to understand a little more about tiled web maps and the parameters of the getTileUrl function we will write. Convert point into web mercator coordinates. There are two primary steps to creating the getTileUrl function: Your getTileUrl is the option required to enable a WMS layer in Google Maps and how we create that tile URL must follow the WMS standard discussed above. Now that we have a basic understanding how the HTTP request to retrieve imagery from a WMS, we can begin exploring the interface Google Maps exposes for its map types, specifically the and. It rose to prominence when Google Maps adopted it in 2005. 
Web Mercator, Google Web Mercator, Spherical Mercator, WGS 84 Web Mercator or WGS 84/Pseudo-Mercator is a constiant of the Mercator projection and is the de facto standard for Web mapping applications. In the above request we are using EPSG:3857, also known as web mercator. It is important to note that the coordinates for the BBOX parameter must be in the coordinate reference system specified by the spatial reference system(SRS).
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