In what coordinate system and unit measures the coordinates returned by the Google Maps API are?

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.

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"]]