Lightning density can be set in 2 ways :
The study of lightning protection requires the consideration of local geographic conditions, in particular the degree of exposure of the structure to the risk of lightning in order to size the necessary “power” of the protection devices to winds considering its architecture in order to determine the necessary mechanical strength of the devices to be installed.
Nk keraunic level shows the average annual value of the number of thunderstorms days (days when thunder is heard in a given place).
Ng lightning density shows the average annual value of the number of lightning strikes per km². In France, the lightning density values are determined by the Météorage network. When the density is not known for a given site, it can be deduced from Nk according to the following relationship.