The way I have always understood it a rod single rod that can't be demonstrated to have <25 ohm of ground contact is not an electrode but that may just be because we live in a sand box and we don't really trust rods that much anyway. I always see rods driven in pairs. That may also be that a rod is $15, 3-point (Fall-of-potential) test from an engineering company is a couple hundred bucks and arguing with an inspector is priceless
