question: How do real time lightning maps detect and track them?
comment: A lightening bolt creates a radio signal. These are easy to pick up. With ~~two or more receivers~~ you can calculate it's position. Edit Should be three or more receivers.
passages: There are a few small area networks (such as Kennedy Space Center's LDAR network, one of whose sensors is pictured at the top of this article) that have VHF time of arrival systems and can detect and position IC flashes. These are called "arrays". They typically cover a circle 30–40 miles in diameter.
  
  Section::::See also.
  
  BULLET::::- Automated airport weather station
  
  BULLET::::- Lightning prediction system
  
  BULLET::::- Convective storm detection
  
  BULLET::::- UK military EMP detectors
  
  BULLET::::- US Military EMP detectors
  
  Section::::External links.
  
  BULLET::::- Vaisala Lightning Detection from Vaisala
  
  BULLET::::- Recent North American lightning activity from StrikestarUS
   Satellite lightning measurements began in 1997 when NASA and National Space Development Agency (NASDA) of Japan launched the Lightning Imaging Sensor (LIS) aboard the aboard the TRMM satellite, providing periodic scan swaths over tropical and sub-tropical portions of the globe until the satellite's was lost in 2015. In 2017 NOAA started deployment of Geostationary Lightning Mappers aboard their GOES-R class satellites, offering continual coverage of much of the land within the western Hemisphere.
   Lightning discharges generate a wide range of electromagnetic radiations, including radio-frequency pulses. The times at which a pulse from a given lightning discharge arrives at several receivers can be used to locate the source of the discharge. The United States federal government has constructed a nationwide grid of such lightning detectors, allowing lightning discharges to be tracked in real time throughout the continental U.S.
   BULLET::::- Storm location: Even in daylight, “storm chasers” can use directional optical detectors that can be pointed at an individual cloud to distinguish thunderclouds at a distance. This is particularly important for identifying the strongest thunderstorms which produce tornadoes, since such storms produce higher flash rates with more high frequency radiation than weaker non-tornadic storms.
   BULLET::::- Tornado Prediction: Severe storms that produce tornadoes are known to have very high lightning rates and most lightning from the deepest convective clouds is IC, therefore the ability to detect IC lightning provides a method for identifying clouds with high tornado potential.
  
  Section::::Lightning range estimation.
   Section::::Description.
  
  The detection equipment is designed to constantly survey atmospheric electrical activity and potential for lightning occurrence via radar and other methods. Storms are scanned by radar to determine the degree of electrification and potential for lightning occurrence.
   Because of the difficulty in obtaining distance to lightning with a single sensor, the only current reliable method for positioning lightning is through interconnected networks of spaced sensors covering an area of the Earth's surface using time-of-arrival differences between the sensors and/or crossed-bearings from different sensors. Several such national networks currently operating in the U.S. can provide the position of CG flashes but currently cannot reliably detect and position IC flashes.
   BULLET::::- Storm identification/tracking: Some thunderstorms, identified by IC detection and observation, make no CG flashes and would not be detected with a CG sensing system. IC flashes also are many times as frequent as CG so provide a more robust signal. The relative high density (number per unit area) of IC flashes allows convective cells to be identified when mapping lightning whereas CG lightning are too few and far between to identify cells which typically are about 5 km in diameter. In the late stages of a storm the CG flash activity subsides and the storm may appear to have ended—but generally there still is IC activity going on in the residue mid-altitude and higher cirrus anvil clouds, so the potential for CG lightning still exists.
   Usually in conjunction with data sources such as weather radar and satellites, lightning detection systems are sometimes utilized to pinpoint where thunderstorms are occurring (and to identify lightning hazard). Currently, most lightning data provided in real-time is from terrestrial sources, specifically, networks of ground-based sensors, although airborne sensors are also in operation. Most of these only provide latitude & longitude, time, and polarity of cloud-to-ground strikes within a limited range. Increasing in sophistication and availability, and affording data for a very wide area, are satellite-based lightning detectors which initially included optical sensors indicating flash rates and horizontal location but now radio frequency receivers that can identify intra-cloud flashes with the addition of altitude, as well.
   Section::::Professional-quality portable lightning detectors.
  
  Inexpensive portable lightning detectors as well as other single sensor , such as used on aircraft, have limitations including detection of and poor sensitivity, particularly for . Professional-quality portable lightning detectors improve performance in these areas by several techniques which facilitate each other, thus magnifying their effects:
   Lightning detection systems have been developed and may be deployed in locations where lightning strikes present special risks, such as public parks. Such systems are designed to detect the conditions which are believed to favor lightning strikes and provide a warning to those in the vicinity to allow them to take appropriate cover.
  
  Section::::Prevention and mitigations.:Personal safety.
   Single sensor lightning detectors have been used on aircraft and while the lightning direction can be determined from a crossed loop sensor, the distance can not be determined reliably because the signal amplitude varies between the individual strokes described above,
   Electronic lightning sensors advanced during the 20th century using radio wave disruptions. Originally the expense of such instruments caused only sporadic development. However a small set of sensors in the U.S. employed during a 1979 project by NOAA’s National Severe Storms Laboratory grew by bits and pieces into the National Lightning Detection Network (NLDN), achieving nationwide coverage in 1989. Vaisala is now the operator and primary distributor of data from the NLDN, and developed the Canadian Lightning Detection Network (CLDN) as of 1998. The EUCLID network is the European shared network, covering most of the continent apart from some far eastern nations. Collaborative amateur development spurred the formation of the Blitzortung community, which offers real-time lightning strike data from most of the world (as well as historical data dating back to 2008) under the Creative Commons license.
   BULLET::::- In New Mexico, U.S., scientists tested a new terawatt laser which provoked lightning. Scientists fired ultra-fast pulses from an extremely powerful laser thus sending several terawatts into the clouds to call down electrical discharges in storm clouds over the region. The laser beams sent from the laser make channels of ionized molecules known as "filaments". Before the lightning strikes earth, the filaments lead electricity through the clouds, playing the role of lightning rods. Researchers generated filaments that lived a period too short to trigger a real lightning strike. Nevertheless, a boost in electrical activity within the clouds was registered. According to the French and German scientists who ran the experiment, the fast pulses sent from the laser will be able to provoke lightning strikes on demand. Statistical analysis showed that their laser pulses indeed enhanced the electrical activity in the thundercloud where it was aimed—in effect they generated small local discharges located at the position of the plasma channels.
   BULLET::::- Early warning: Detection of IC flashes is important because they typically occur from 5 to 30 minutes before CG flashes [source?] and so can provide earlier warning of developing thunderstorms [source?], greatly enhancing the effectiveness of the detector in personal-safety and storm-spotting applications compared to a CG-only detector [source?]. Increased sensitivity also provides warning of already-developed storms which are more distant but may be moving toward the user. [source?]
   BULLET::::- Since they use attenuation rather than triangulation, mobile detectors sometimes mistakenly indicate a weak lightning flash nearby as a strong one further away, or vice versa.
  
  BULLET::::- Space-based lightning networks suffer from neither of these limitations, but the information provided by them is often several minutes old by the time it is widely available, making it of limited use for real-time applications such as air navigation.
  
  Section::::Lightning detectors vs. weather radar.
   However, since RF signals and light pulses rarely occur simultaneously except when produced by lightning, RF sensors and light pulse sensors can usefully be connected in a “coincidence circuit” which requires both kinds of signals simultaneously in order to produce an output. If such a system is pointed toward a cloud and lightning occurs in that cloud, both signals will be received; the coincidence circuit will produce an output; and the user can be sure the cause was lightning.
   The exact location of a lightning strike or when it will occur is still impossible to predict. However, products and systems have been designed of varying complexities to alert people as the probability of a strike increases above a set level determined by a risk assessment for the location's conditions and circumstances. One significant improvement has been in the area of detection of flashes through both ground and satellite-based observation devices. The strikes and atmospheric flashes are not predicted, however the level of detail recorded by these technologies has vastly improved in the past 20 years.
   BULLET::::- Enhanced Intracloud Lightning Detection: The addition of an optical sensor and coincidence circuit not only eliminates false alarms caused by RF noise; it also allows the RF sensor to be operated at higher sensitivity and to sense higher frequencies characteristic of IC lightning and enable the weaker high frequency components of IC signals and more distant flashes to be detected.
  
  The improvements described above significantly extend the detector's utility in many areas:
   When a lightning discharge occurs within a cloud at night, the entire cloud appears to illuminate. In daylight these intracloud flashes are rarely visible to the human eye; nevertheless, optical sensors can detect them. Looking through the window of the space shuttle in early missions, astronauts used optical sensors to detect lightning in bright sunlit clouds far below. This application led to development of the dual signal portable lightning detector which utilizes light flashes as well as the “” signals detected by previous devices.
   BULLET::::- A ground-based lightning network must be able to detect a flash with at least three antennas to locate it with an acceptable margin of error. This often leads to the rejection of cloud-to-cloud lightning, as one antenna might detect the position of the flash on the starting cloud and the other antenna the receiving one. As a result, ground-based networks have a tendency to underestimate the number of flashes, especially at the beginning of storms where cloud-to-cloud lightning is prevalent.
   BULLET::::- Rocket-triggered lightning can be "triggered" by launching specially designed rockets trailing spools of wire into thunderstorms. The wire unwinds as the rocket ascends, creating an elevated ground that can attract descending leaders. If a leader attaches, the wire provides a low-resistance pathway for a lightning flash to occur. The wire is vaporized by the return current flow, creating a straight lightning plasma channel in its place. This method allows for scientific research of lightning to occur under a more controlled and predictable manner.
   In more contemporary times, thunderstorms have taken on the role of a scientific curiosity. Every spring, storm chasers head to the Great Plains of the United States and the Canadian Prairies to explore the scientific aspects of storms and tornadoes through use of videotaping. Radio pulses produced by cosmic rays are being used to study how electric charges develop within thunderstorms. More organized meteorological projects such as VORTEX2 use an array of sensors, such as the Doppler on Wheels, vehicles with mounted automated weather stations, weather balloons, and unmanned aircraft to investigate thunderstorms expected to produce severe weather. Lightning is detected remotely using sensors that detect cloud-to-ground lightning strokes with 95 percent accuracy in detection and within of their point of origin.
   Ground-based and mobile detectors calculate the direction and severity of lightning from the current location using radio direction-finding techniques along with an analysis of the characteristic frequencies emitted by lightning. Ground-based systems use triangulation from multiple locations to determine distance, while mobile systems estimate distance using signal frequency and attenuation. Space-based detectors on satellites can be used to locate lightning range, bearing and intensity by direct observation.
   BULLET::::- Human sensory acuity is not as fine as that of the milliseconds duration of a lightning flash, and our ability to observe this event is subject to the brain's inability to comprehend it. Lightning detection systems are coming online, both satellite and land based, however their accuracy is still measured in the hundreds to thousands of feet, rarely allowing them to pinpoint the exact location of the termination.
  
  As such it is often inconclusive, albeit highly probably a lightning flash was involved, hence categorizing it as a "lightning incident" covers all bases.
  
  Section::::Notable incidents.:Earth-bound.
  