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How It WorksWhen a lightning strike occurs an extremely strong electromagnetic field is generated. Part of the signal produced can be heard on an AM radio receiver when a storm is in the area. 
The Kattron network consists of a number of sensors which contain sensitive radio receivers monitoring the 2-450kHz radio band. (This is below the AM Broadcast band.) The sensors digitise the stroke waveform and record details of the stroke including it’s peak amplitude and polarity, and the time the signal arrived at the sensor (as recorded using the extremely accurate GPS timing signals). The time the signal takes to arrive at a sensor depends on it’s distance from the stroke. In the diagram below the circles represent the time taken to reach the sensors.
The stroke details are immediately sent via a communications network to a central computer. This computer uses the time of arrival of the signal at the sensor in complex algorithms to determine the location of the stroke. The basic principle is described below. 
If two sensors detected the signal from a lightning stroke at the exactly the same time the signal source is a point on a straight line equidistant from both sensors. (See the diagram below). 
If the two sensor detected the signal at slightly different times, the signal source is a point on a hyperbola where the distance from each sensor is proportional to the difference in the time of arrival. (See the diagram below). 
To determine where along the hyperbola the stroke occurred, a third sensor is required. This third sensor produces a second hyperbola which crosses the first. (See the diagram below) A fourth Sensor adds a third hyperbola and can be used to verify the location of the stroke. The stroke details are then archived for historical analysis, and transmitted in real time to customers computers where they are displayed on a map. The whole process from the stroke occurring to it’s arrival at a customers site can take less than a few seconds, in some cases all this happens before the thunder is heard by observers. (Thunder takes 3 seconds to travel 1 km.) Kattron operate a lightning data service using a tracking network called Lightning Positioning And Tracking System ( LPATS ). The data from the Australian owned and operated Kattron Lightning Detection Network is used in many applications. The network consists of equipment supplied by Global Atmospherics Inc who manufactured over 95% of the worlds installed lightning detection networks, and who own and operate the North American Lightning Detection Network which is used by organisation including NASA Kennedy Space Centre, NOAA's National Severe Storms Laboratory, Electric Power Research Institute (EPRI) and Universities, along with a wide range of meteorology, aviation, electric power, insurance, and forestry authorities throughout the world. |
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