SG-1 and SGU had real stargate set pieces erected on location. Not always, but often. Now, in Atlantis, it seems to always be CGI. We never see an off world stargate for very long, and when we do, it always looks CGI. Did they have a Pegasus stargate pet piece for episodes set off world? If not, it would explain why SG-1 and SGU had stargates with pedestals while SGA had them partially buried in the ground (the bottom part).