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How does my local weather station create these lightning strike maps?

• My local weather station puts up these maps that show the lightning strikes detected in the last ten minutes. How is that map generated? What sensor do they have that can show the exact (near-exact?) position of a lightning strike? How does the sensor work? I don't think it is their doppler radar because that is a rotating antenna. If it was pointing the wrong way when the strike occurred, the radar wouldn't see it. Plus the strike is so quick I don't think there would be any radar signature.

• Answer:

  Lightning detectors are essentially low frequency radio receivers.  With a widespread national network of these special receivers, a single lightning strike will be heard by many receivers.  Since radio waves travel at the finite speed of light, the pulse of radio signal that is generated by lightning expands outward as a spherical shell at the speed of light.  A similar, though much slower, phenomenon is the visible shockwave of explosions.  As the radio wavefront passes receivers, each receiver records the time precisely.  Then the reception times are compared to nearby receivers, and triangulation is used to pinpoint the source location.  Your local weather station is likely just taking their map data from the national lightning detector network. More info: http://gcmd.nasa.gov/records/GCMD_NLDN.html