Spherical or Web Mercator Coordinate System

Liz Sanderson
Liz Sanderson
  • Updated

FME Version

  • FME 2015.x

Question

What is Web Mercator?

Answer

Web Mercator, also known as Spherical Mercator, is the coordinate system used by web mapping tools such as Google Maps or Bing Maps.

The FME name for Web Mercator is SPHERICAL_MERCATOR or EPSG: 3857. The deprecated EPSG: 3785 or EPSG: 900913 coordinate systems are also occasionally used for Web Mercator.

Web Mercator is a meters based projection that encompasses the entire world, except for the polar regions (latitudes -85 to 85). This makes it suitable for displaying a wide variety of source datasets, but not for accurate measurement.

If you are using the WebMapTiler to create Google Maps or Bing Maps compatible tiles, the source image must be in the Web Mercator projection. You can use the Reprojector or CsmapReprojector transformers to reproject the image data before tiling.

Please note that Google Earth KML files should not be written in Web Mercator. Instead, please use LL-WGS84 (EPSG:4326).

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