Are the datum and the ellipsoid the same? What is a Datum?

The Earth is shaped like a flattened sphere. This shape is called an ellipsoid. A datum is a model of the earth that is used in mapping. The datum consists of a series of numbers that define the shape and size of the ellipsoid and it's orientation in space. A datum is chosen to give the best possible fit to the true shape of the Earth. in this article....

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    Please refer to this Q&A to get a response (or at least part of it) : gis.stackexchange.com/questions/664/… – simo Mar 10 '14 at 8:14
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    It might also help if you can tell us what research you've already done. – BradHards Mar 10 '14 at 11:05
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    actually this is not a duplication. he asked about ellipsoid-vs-datum and the Q you refer to is projection-vs-datum. the answer is: ellipsoid is a 3d mathematical surface. a datum consists of an ellipsoid + more parameters. for example the same ellipsoid can be set at different positions and orientations and then you'l have different datums – dowi Sep 28 '14 at 8:25
  • For some reason I was unable to re-open this question when I tried to just now. In any event, I think it is a duplicate of gis.stackexchange.com/questions/175293/… instead of the Q&A to which it is currently assigned. – PolyGeo Dec 31 '15 at 1:27