Lightning detection methods

Mostly used lightning detection method in the past was Magnetic Direction Finding (MDF) method. Method based on detection of  lightning electromagnetic wave direction. Later, Time Of Arrival (TOA) method was developed. TOA method measures time difference between lightning and lightning detection by sensor. Based on that time, distance of lightning form the sensor is determined. Modern sensors nowadays uses combined method for lightning detection. With combined method time and location of lightning strike is accurately determined.

Magnetic Direction Finding (MDF) method

To determine lightning strike location with MDF method at least two sensors are needed. Sensors detect azimuth (angle between north and direction towards lightning strike) between the sensor and lightning. That is the way to "draw" line through the sensor and lightning hit point. With at least two lines (from two or more sensors) intersection of those lines is calculated. Intersection represents the exact location of lightning. With the use of several sensors the lighting strike position offset is reduced.

Above picture shows determination of the direction from sensor to lightning. Electric field caused by lightning, causes the magnetic field (vector marked with B). The magnetic field is always perpendicular to electric field, so with the determination of magnetic field, lightning direction is determined. With two or more sensors the exact location of lightning can be calculated.

in some cases, when lightning hits on the line between two sensors, location can not be determine only with two sensors. In that case at least three sensors are needed.

Time Of Arrival (TOA) method

Combined method

New generation of sensors uses TOA and MDF method. This method is also named Combined method. Those sensor provides azimuth between sensor and lightning hit point and exact UTC time. With those sensors exact time and location of lightning is determined.

This method has no problems that are specific to a particular method. With using Combined method only two sensors are enough to determine lightning position. More sensors contributes to accuracy of lightning time and position.

First direction vectors are used for lightning position evaluation, then with the time differences the exact lightning location is determined.