About

Web Mercator a.k.a WGS 84 / Pseudo-Mercator -- Spherical Mercator, is a projected coordinate system used for rendering web maps in applications like Google Maps and OpenStreetMap. The area of use is limited to World maps between 85.06°S and 85.06°N.

Currently agreed code to represent Web Mercator is: EPSG:3857

PROJCS["WGS 84 / Pseudo-Mercator",
GEOGCS["WGS 84",
    DATUM["WGS_1984",
        SPHEROID["WGS 84",6378137,298.257223563,
            AUTHORITY["EPSG","7030"]],
        AUTHORITY["EPSG","6326"]],
    PRIMEM["Greenwich",0,
        AUTHORITY["EPSG","8901"]],
    UNIT["degree",0.0174532925199433,
        AUTHORITY["EPSG","9122"]],
    AUTHORITY["EPSG","4326"]],
PROJECTION["Mercator_1SP"],
PARAMETER["central_meridian",0],
PARAMETER["scale_factor",1],
PARAMETER["false_easting",0],
PARAMETER["false_northing",0],
UNIT["metre",1,
    AUTHORITY["EPSG","9001"]],
AXIS["X",EAST],
AXIS["Y",NORTH],
EXTENSION["PROJ4","+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext  +no_defs"],
AUTHORITY["EPSG","3857"]]

From: http://epsg.io/3857

In the past Web Mercator has been referenced with the following codes:

  • 54004 Google Maps uses this projection, in decimal degrees, others meters sometimes (sometimes equivalent?)
  • OSGEO:41001 - OSGeo created this code while developing the Tile Map Service (TMS) specification. [1] It was superseded by 900913. (equivalent, deprecated)
  • 900913 (i.e. GOOGLE) - Sometimes described as EPSG:900913, this was created for OpenLayers (equivalent)
  • ESRI:102113 - First used by ESRI, but then replaced by 102100 (equivalent, deprecated)
  • ESRI:102100 - Built differently, but equivalent to 102113 (equivalent, deprecated)
  • EPSG:3785 - EPSG added this, similar to how ESRI:102113 is defined (equivalent, deprecated)
  • EPSG:3587 - was never a real EPSG code, but some used this likely as a mistype of EPSG:3785 (mistype)
  • EPSG:3857 - EPSG replaced EPSG:3785 with this, and ESRI replaced ESRI:102100 with this (current)

Modified from https://wiki.openstreetmap.org/wiki/EPSG:3857

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