The Los Alamos Sferic Array (LASA) was originally built for ground
verification of lightning observations by the FORTE satellite. LASA
has evolved into a tool for studying both FORTE and GPS lightning
observations, as well as a stand alone tool for studying lightning.
LASA is an array of LF/VLF electric field change meters which is
digitized at 1 MHz with 12 bit resoltuion. Each LASA station utilizes
GPS receivers to provide absolute event time tagging with an accuracy
of better than 2 
s. Using differential time of arrival methods
for the event times at multiple stations, lightning events are
geo-located. Most commonly, LASA records are 8 ms in duration and
have been collected by a threshold triggering mechanism that includes
2 ms of pre-trigger data. Based on initial investigation into
intracloud and leader LF/VLF radiation, 80 ms and 1 s records were
collected by LASA stations to provide stroke context.
During operations of the sferic array from 1998 through the present,
stations have been located in the United States, in the states of New
Mexico, Texas, Nebraska, Colorado, and Florida.
[Smith et al.(2002)] describe the operation and
instrumentation of LASA and characterize the accuracy of LASA
geolocation. The classification of NBEs is also describe in detail.
Briefly, the NBEs are distinct based on the relative lack of
neighboring radiation (or the isolation) and the narrow nature of the
signature (the rise time and the fall time of the waveform). The
classification of CG events is based solely on the relatively slow
(greater than 30 s) fall time.