Lightning and information about out detection
system.
The system we use is a BOLTEK
STORMTRECKER PCI CARD. Below you will find information on
how this works.
Our lightning detection center is
powered by a Boltek StormTracker PCI. StormTracker works by
detecting the radio signals produced by lightning. These are the same
signals you can hear as static
on an AM radio during a thunderstorm.
StormTracker's antenna is a small black
box (3"x2"x1-1/2") which may be mounted indoors
(in a wood framed house for example) or outdoors. It consists of a
crossed loop magnetic
field sensor and electric field sensor. The antenna is typically
mounted ten to twenty feet above
the ground, away from large metal objects and sources of electrical
noise such as televisions
and computer monitors.
The antenna is very sensitive to
electro-magnetic interference. The key factor in reducing
interference is to mount the antenna well away from potential noise
sources. Apart
from this, the detector will only record a signal when it detects an
abrupt change in the
electric field. If the antenna is mounted correctly, this will only
occur for lightning strokes.
The antenna is connected to a PC via a
Cat5 data cable. This goes into Boltek's special
PCI card where the signals are digitized for processing by
software.
Our StormTracker antenna is mounted
outdoors, inside a custom made 9" long PVC
tube enclosure, approximately 25 feet off the ground. It is located
at the northern
end of the building, well above the roof, to minimize interference
and enhance
reception. In this location, it can detect storms reliably 350 miles
or more away.
While the StormTracker can only detect
1 stroke at a time, it can detect up to 3,000
to 3,500 strokes per second. According to Relko Dimitrijevic with
Astrogenic
Systems, the highest reported stroke rate to date was slightly over
2,100
per minute - recorded in Australia in 2005.
A product of Astrogenic Systems,
Nexstorm is a Microsoft Windows 32-bit application for
use with the Boltek StormTracker ISA card, PCI card, and LD250
lightning detectors.
NexStorm combines display, analysis,
networking and interprocess communication
functionality in a way that makes this software package the most
versatile lightning
display and analysis application available on the market. Without
this software,
the Boltek StormTracker would be practically useless.
The software determines stroke type at
the software level. For each electro-magnetic
pulse that occurs (i.e. for each lightning stroke) the software will
obtain a signal
waveform which is analyzed in real time.
There are numerous signatures in
a waveform that can tell what type of stroke it was.
To determine polarity (positive or negative) the software looks at
the electric field
at various points in the waveform. To determine the type (cloud to
ground or cloud
to cloud), the software looks at total waveform length, rise times to
peak, peak
to zero crossing times, etc.
Direction is determined by looking at
the magnetic field ratios for each stroke and
using basic trigonometry, i.e. crossed loop antenna direction finding
principle.
Initial distance is determined by
looking at the signal strength. This however is not
very reliable because the signal strength of various strokes occuring
at the
same exact distance will vary a lot depending on released energy.
Therefore,
in single antenna lightning detection systems, Nexstorm averages each
stroke
against a cluster of other strokes that are located towards the same
direction,
and from that derive a distance to the entire storm cell.
Thunderstorm Ranging and Acquisition,
or TRAC for short, is a sub-process in
NexStorm that contains all the logic behind computing where
thunderstorms are
located and analyzing their characteristics. TRAC can also produce a
text-based
report based on its findings to show you details about individual
storms. The TRAC
related on map identification feature uses TRAC data to display
important information
about a thunderstorm. When TRAC has detected what it believes to be a
structured
thunderstorm system, it will start tracking it until the storm
dissipates or the
tracking could not be maintained for other reasons.
^ - v indicates if storm is increasing, steady, or
decreasing.
TRAC will periodically generate a
report based on current activity. This is called
the TRAC report. While a thunderstorm is being tracked it is also
being continuously
analyzed. You can view the results of the real-time analysis in the
TRAC report.
