Analysis of the French lightning locating system location accuracy

The location accuracy is one of the important parameters characterizing the performance of a lightning location system. It is also one of the most difficult to determine as the actual location of the discharge being located must be accurately known to achieve a reliable assessment of the real error. Among all the measurement techniques which can be used to collect such ground truth data, none can cover large area preventing the estimation of the location accuracy at a regional or national scale. Trying to get around this limitation, Météorage has developed a method based on lightning ground strike point data collected by the French national lightning locating system computing the separation distances of return strokes identified as using the same attachment point on the ground. As a result, statistics on the relative location accuracy over the last 10 years of operation at the national scale are produced. In order to determine whether this data could be a proxy for the absolute location accuracy they are compared against systematic errors estimated in the vicinity of high elevation towers well known to attract or trigger lightning. If the study shows some discrepancies between relative and absolute errors at the beginning of the period, mainly due to technological upgrades in the system, it turns out both parameters fit nicely since 2010. This tending to demonstrate the relative errors estimated based on the ground strike point can be used as a good proxy for the absolute location errors estimate.