I am wondering about WGS84 as we move through time.
My understanding is that any given spot on the earth's surface latitude and longitude will change over time in this system. There are two sources of change:
1) NGA (National Geospatial-Intelligence Agency) will periodically shift the center of the WGS84 ellipsoid to better align with their current best guess for the center of the earth's mass (I think they are using a geoid to find the center of mass). At which time the will release a new version of the WGS84 and note the GPS weeks in the name, e.g. WGS84 (G1150).
