It's even stranger. NAD83, the North American Datum is tied to the North American plate. In the 80's, NAD83 and WGS84 were essentially identical - differed by millimeters. Now they are several feet apart as the North American plate moves about 1 cm per year.
Many years ago (early 80's) I taught a short class in geodetics, and a geodecist I worked with made a viewgraph for me showing how a particular well offshore Angola would move by up to a kilometer depending on which geodetic datum you attached its lat-long to. There are many local datums, designed to better approximate local topography. I spent a lot of effort teaching people that knowing the lat-long of a point did NOT tell you where it was on the earth. You also needed to know the datum.
It's even stranger. NAD83, the North American Datum is tied to the North American plate. In the 80's, NAD83 and WGS84 were essentially identical - differed by millimeters. Now they are several feet apart as the North American plate moves about 1 cm per year.
Many years ago (early 80's) I taught a short class in geodetics, and a geodecist I worked with made a viewgraph for me showing how a particular well offshore Angola would move by up to a kilometer depending on which geodetic datum you attached its lat-long to. There are many local datums, designed to better approximate local topography. I spent a lot of effort teaching people that knowing the lat-long of a point did NOT tell you where it was on the earth. You also needed to know the datum.