For those interested in technical details about geoid modeling from the seventies to 2014, I recommend reading Lars Sjoberg's article at the linked site. Interesting stuff. The whole issue is open access with the other articles including one one gravimetric geoid modeling in Uganda.
http://www.degruyter.com/view/j/jogs.2015.5.issue-1/issue-files/jogs.2015.5.issue-1.xml
Enjoy,
DMM
Thanks for the link! Having started my own geodetic journey slightly later than Sjoberg's (I was at OSU from 1982-85, under the guidance of the "holy trinity" of Mueller, Rapp & Uotila), I'd concur with Lar's perspective. Geoid modeling has really improved since 1984. EGM2008 is amazingly superior to the GEM models of the late 80's, that I had a hand in. Surprisingly, the progress in theory hasn't quite kept pace with the progress in the technology. But then Mueller taught that theory and technology leap-frog one another.