IEC 62858-2015 pdf Lightning density based on lightning location systems (LLS) – General principles

5 Validation of lightning location system performance characteristics The performance characteristics of an LLS determine the quality of the lightning data available. These performance characteristics include: – detection efficiency for IC and CG flashes and CG strokes; – location accuracy; – peak current estimation accuracy; and – lightning classification accuracy. As stated in Clause 4, for N G and N SG determination of CG flash DE, LA, and lightning, classification accuracy is of primary importance. These performance characteristics can be evaluated using a variety of techniques which are summarized below. a) Network self-reference: In this technique, statistical analysis of parameters (e.g. [1 1 ]) such as standard deviation of sensor timing error, semi-major axis length of the 50 % confidence ellipse, and the number of reporting sensors, is used to infer the LA and DE of an LLS. Examples of such studies are found in [4] and [7]. This method requires data collected by the network after it has been properly calibrated. It can provide a good estimate of the network’s performance in a cost-effective, practical manner. b) Rocket-triggered lightning and tall object studies: This method uses data from rocket- triggered lightning experiments or lightning strikes to tall objects (e.g., instrumented towers) as ground-truth to evaluate the performance characteristics of an LLS within whose coverage area the triggered lightning facility or the tall object is located. The LA, DE, peak current estimation accuracy, and lightning classification accuracy of an LLS can be measured using this method. Examples of studies using rocket-triggered lightning for LLS performance evaluation include [6], [8], and [1 2], [1 3].
Video camera studies: Lightning data obtained using video cameras can be used as ground-truth to evaluate the performance characteristics of an LLS within whose coverage area the lightning discharges occur. The LA, DE and lightning classification accuracy of an LLS can generally be estimated using this method. Examples of studies using video camera for LLS performance evaluation include [1 ] and [1 4]. In this method, data collection can be time-consuming and challenging because the exact locations of lightning discharges to be captured on video cannot be predicted. Additional instrumentation such as antennas measuring electric field from lightning discharges is often required for this technique.