The International Electrotechnical Commission has published a new standard, IEC 62858:2015. IEC62858 applies to “Lightning density based on lightning location systems (LLS).” The standard is available for purchase on the IEC’s website.
“IEC 62858:2015 introduces and discusses all necessary measures to make reliable and homogeneous the values of NG obtained from LLS in various countries. Only parameters that are relevant to risk assessment are considered.”
*Description from IEC Website