To perform a calculation, you need the radius of the sphere. This is determined by the chosen for the building.
Modern architecture rarely features flat, simple roofs. Calculators allow you to input varying heights ( ) and distances ( rolling sphere method calculator
A smaller sphere (Level I) is more "touchy" and will probe into every crevice, providing the highest level of protection. A larger sphere (Level IV) offers less stringent protection, suitable for ordinary structures. To perform a calculation, you need the radius of the sphere
The sphere’s radius is not arbitrary. It is derived from the formula, which relates to the peak lightning current. The most common standard (IEC 62305 and NFPA 780) defines protection levels (I to IV) with corresponding sphere radii: To perform a calculation