ATDnet
Arrival Time Difference Network

The Arrival Time Difference Network (ATDnet) is a ground-based lightning detection network operated by the United Kingdom Meteorological Office. It consists of several sensors across Europe that detect lightning in Europe, northern Africa, and the northern Atlantic Ocean. It uses very-low-frequency (VLF) sensors to detect the electromagnetic waves or sferics generated by lightning strikes to determine the number and location of lightning strikes. These sensors operate at a central frequency of 13.733 kHz and have a time resolution of 1 ns. ATDnet has a location accuracy of 1-3 km.