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Typical lightning strikes in Texas are recorded on 9 to 12 sensors. The times are compared, and locations are triangulated. The key data in the NLDN database starts when electrical currents raise above background electrical noise, measring the Rise-Time it takes to reach Peak Current, and then the Peak-to-Zero time back to the background noise. From this we calculate the Total Wavelet Time and the Wavelet Symmetry. Most strikes are negative polarity, coming from the bottom of the clouds. Positive polarity strikes occur at the end of a thunderstorm, come from the tops of the clouds, and are much stronger. Chi Squared is a quality measurement. As we have learn more about this data, we have been able to derive other electrical properties tied to the earth and geology.

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