"Mayotte is on the move. Since mid-July, GPS stations on the island have tracked it sliding more than 2.4 inches to the east and 1.2 inches to the south."
If this isn't a mistake, it's also very interesting. 2.7 inches in four months is very fast. That's 20 cm/year. The fastest techtonic plates move about 10 cm/year. Also this island does not appear to be near a plate boundary, so what could make it move? The article didn't say what it was moving relative to.
Since it's a magma body moving Mayotte, Mayotte could be moving relative to it's place on the plate?
> [After the 2010 Chile earthquake] A research collaborative of Ohio State and other institutions have found, using GPS, that the earthquake [...] moved Concepción at least 3 metres (10 ft) to the west. [...] Several cities south of Cobquecura were also raised, by up to 3 meters.
For instance many survey instruments use Differential GPS to obtain a more precise location by using corrections from a receiver at a well-established survey mark. When using DGPS the coordinate system becomes that of the reference mark, not the GPS system.
So I think the question is relevant, and takes note of the context in which ground motion is studied.
These things are in use in the 100's of thousands in agriculture now. Such base stations record their ground point by GPS location.