Lightning position and tracking method

#The present invention relates in general to lightning detection systems and, more particularly, to a system for accurately determining the position of a lightning discharge to ground.

#Storm warning systems, particularly those which monitor the electrical discharge activity attendant to the storms, employ various types of direction finding and/or range finding equipment. Typically, the systems are designed to be responsive to the characteristics of the lightning stroke and to generate an indication of the occurrence of a stroke and the direction or position from which the stroke originated. Examples of such systems which seek to provide position information may be found in U.S. Pat. Nos. 4,115,732 and 4,245,190 to Krider et al; 4,023,408 to Ryan et al; 3,369,240 to Leary; 3,754,263 to Wojtasinski et al; 2,684,474 to Kass; and 3,386,553 to Bates.

#Other types of systems seek principally to determine the direction or bearing of the discharge. Examples of these types of systems may be found in the U.S. Pat. Nos. 1,759,938 to Dean; 3,603,951 to Bracken et al; 4,236,159 to Alpers; 4,210,913 to Newhouse et al; and 4,198,599 to Krider et al.

#FIG. 1 is a block diagram of the overall lightning ground stroke locating system according to the present invention;

#FIG. 2 is a block diagram of an individual one of the receiving stations shown in FIG. 1;

#FIG. 3 is a schematic block diagram of a LORAN-C receiver;

#Referring now to FIG. 1, wherein a block diagram of the lightning ground stroke locating system according to the present invention is illustrated, distributed geographically throughout a region of interest are a plurality (four in the embodiment shown in FIG. 1) of lightning detection/listening stations 10, 20, 30 and 40, each of which includes a respective antenna 11, 21, 31 and 41 for receiving a time synchronization signal-containing carrier from a timing signal source 60. As explained briefly above, preferably, timing signal source 60 corresponds to one of the presently avialable LORAN-C group transmitting stations located throughout the United States. For the purposes of the present description, it will be presumed that transmitting station 60 is a master group station transmitting the LORAN-C carrier via an associated antenna 61.

#It should be noted that although familiarity with LORAN-C navigation systems and signalling formats is a general requisite for an understanding of the description of the present to follow, the basic characteristics of LORAN-C signalling will be explained briefly below in conjunction with the description of the individual units of a receiving station, in order to provide a full appreciation for the timing signal synchronization aspects of the invention. Of course, for further educational background purposes concerning LORAN-C signalling and timing formats, attention may be directed to various reference literature, such as the LORAN-C User Handbook, U.S. Coast Guard, Frequency Dissemination Via the LORAN-C System, by C. E. Potts et al, proc. I.E.E.E., vol. 60, pp. 530-539, May 1971, for example.

#Each receiving station is coupled by a respective communication link 15, 25, 35 and 45 to a central processing facility 50, typically remotely located relative to the receiving stations, such as at a weather station, an airport, etc. Each receiving station further includes an electromagnetic pulse field detector (not shown) for detecting the occurrence of a lightning ground stroke from some arbitrary location 70. When a ground stroke occurs, the electromagnetic pulse is detected at each listening station 10-40, and the time of occurrence of the detection of that ground stroke is recorded by sampling a free running clock within the station, which is internally synchronized with the clock signal generated at station 60. In effect, each listening station 10-40 records the time that the stroke is detected relative to this standard timing cycle emitted by station 60. A respective digital time byte is then transmitted from each listening station to the central processing facility 50, via communication links 15-45.