What’s their relationship or difference?

I’ve read that WGS84 uses ECEF, but they can be converted between one another. If not mistaken, they are both geographic coordinate systems and not projected coordinate systems. But that’s about all I understand.

  • See en.wikipedia.org/wiki/ECEF and en.wikipedia.org/wiki/…
    – TomazicM
    Commented Feb 17, 2021 at 8:58
  • @TomazicM That doesn't answer my question. They are both coordinate systems, so what's their difference between their purpose? I've also read that WGS84 uses ECEF, but that in and of itself doesn't make sense to me.
    – pstatix
    Commented Feb 17, 2021 at 14:21

1 Answer 1


The ECEF that is used for the Global Positioning System (GPS) is the geocentric WGS 84, which currently includes its own ellipsoid definition Wikipedia

So actually, WGS 84 is an ECEF. Both are reference systems, but WGS 84 provides an additional:

  • a horizontal datum (reference point to measure the change in position when the latitude or longitude changes. Vertical datum is for changes in altitude.)

Different standards (e.g. WGS 72, NAD83, ETRS89) use different datums.


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