Google Maps API – Understanding Coordinate System and Units

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In what coordinate system and unit measures the coordinates returned by the Google Maps API are?
I ask this because I have a page that returns the geocode lat / long for me to find in my postgis basis. But the query does not return anything, I need to know which projection should I work with my data.

Best Answer

Google Maps, like most web maps, works in WGS84, Web Mercator (Auxiliary Sphere) - EPSG 3857. http://spatialreference.org/ref/sr-org/epsg3857-wgs84-web-mercator-auxiliary-sphere/

Planar units are meters.

Also, see this similar question.

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"]]
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