Can someone explain this method. When I roll a sphere over a building it's center creates surface. What does this surface means? Can this method be used without software?
I have no idea what the sphere method is. In the USA lightning protection gounding is determined by following the IEEE standard, the Green Book, Standard No. 142, Chapter 3.
Search through Australian (AS1768) or British standards on lightning protection and you will find answers as to what the sphere method is and how to apply it. Basically the rolling sphere method is a means of determining the area which will be protected by a lightning air terminal (Lightning rod) and thus a means of determining how many air terminals are required and where they need to be placed in order to protect a given area from lightning strike.