For any of you in the surveying business, WGS-84 is probably a regular part of your vocabulary, but in his GPS World article entitled Accuracy, Datums, and Geospatial Data..., Eric Gakstatter cautions to the contrary, stating the following:
"First, let me begin with the statement that WGS-84 should not be in your geospatial vocabulary. In fact, I’ve been corrected in the past that it is actually a reference frame rather than a datum, but you’ll likely see it listed as a datum in your geospatial software. WGS-84 is not something you’ll find physical marks on the ground that you can use to verify GNSS equipment performance. WGS-84 is defined by the U.S. National Geospatial-Intelligence Agency (NGA), which serves the U.S. Department of Defense and the U.S. Intelligence Community. In other words, one of its roles doesn’t include serving the civilian community. Originally, the accuracy of data referenced to WGS-84 could not be defined more accurately than a couple of meters. In fact, the definition of WGS-84 has changed several times over the years, usually without your knowledge, and usually not accounted for in the geospatial software you are using."
Eric also notes that one of the many issues with WGS-84 is that it does not account for tectonic plate movement. This image is provided compliments of the University of Kentucky, and shows approximate plate velocity in cm/year. So if you thought you were sitting still, think again...
In the same article, Eric also provides some details and possible repurcussions of the July 2, 2013 crash of the rocket carrying 3 GLONASS satellites. Despite this setback, the GLONASS system still has a full 24-satellite constellation.