There is a difference between grounds from an electrical and noise point of view.
Earth Ground is Earth Ground is Earth Ground, Earth Ground does not change into something else when being used for noise abatement. While the primary purpose of the ground wire being added to electrical system was safety having a low impedance path to earth (a path which had no current flow from any circuit) was also a perfect place to bleed off electrical noise.
A copper ground rod is for safety - it will do nothing at all for noise.
That is incorrect. Crack open the power supply on your PC, where do all the filter parts get bonded to? The Earth Ground! Why? It is a low impedance path to ground. In the case of a machine like a Plasma Cutting table, Automated TIG welding machine etc, the local ground rod provides a low impedance path to the earth rather than rely on the small gauge ground wire that runs all the way back through the plant to the electrical service entrance. Any local ground rod should be bonded to the buildings electrical ground to prevent a potential shock hazard between the two.
I'm not meaning to sound like a 'know-it-all' here, I just want to dispel myths about grounding. I used to design, install and service automated welding and cutting systems and have had first hand experience with about every type of noise issue there is. I just want to share that experience with others.