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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.

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    What do you mean with Google Maps API, and could you show a sample request and response? For example the geocoding API, with request maps.google.com/maps/api/geocode/… returns coordinates as Lat/Long coordinates, thus in EPSG:4326. Are you sure that you have not accepted a wrong answer? – user30184 Oct 26 '17 at 10:31
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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"]]
  • I was under the impression units in WGS84 were decimal degree? – Erica Jun 10 '14 at 13:34
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    WGS84 is decimal degree as a geographic coordinate system, but WGS84 is just the datum when put into a flat projected coordinate system. Web Mercator is such a system. There are many different projections of WGS84. EPSG 4326 is a projected system that takes lat/long decimal degrees as planar units. spatialreference.org/ref/epsg/wgs-84 – Wes Jun 10 '14 at 13:42
  • I agree with your first sentence, but EPSG 4326 is not a projected coordinate system, it is a geographic coordinate system. – radouxju Jun 10 '14 at 13:55
  • Well, it is and it isn't. EPSG 4326 is the two dimensional definition of the three dimensional WGS84. But yeah, functionally they are the same thing. – Wes Jun 10 '14 at 14:01
  • This is a common argument. See Dan S.'s argument in this thread. I fall on that side of the argument--they are the same except in the nitty gritty: gis.stackexchange.com/questions/3334/… – Wes Jun 10 '14 at 14:03
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Planar units: meters. Google maps API employs a metric (not an imperial) system of measuring quantities. Well, Google maps co-ordinates are in degrees (decimal points), although these co-ordinates are generated in radians. 1 radian equals 57.296 degrees.

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I hope I was clear when I stated that the co-ordinate points given by google maps are in degrees. By reporting the degrees in decimal point form, we avoid using North, South,East and West so that we can remain digital. The 1995 decision of the International System (SI) for measuring quantities to treat an angle as a derived quantity from a base quantity,length, resolved almost all the problems that were emanating from the use of an imperial system of measuring quantities.

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Planar units: meters. Google maps API employs a metric (not an imperial) system of measuring quantities.

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