Purpose: The TREMBLE system is designed to provide near-real-time visualization of lightning occurring within a 10-mile radius of a chosen recording station. Once the hardware and software is installed, it can be used by someone with minimal computer skills. Both the visualization program, Crossbow, and the scheduling program, StormTracker, feature VCR-like controls to ease set up and navigation.
Usage: Our visualization program, Crossbow, allows a user to view lightning strikes as they happen or from a previously recorded data set. Crossbow runs on either a PC or a high-end graphics workstation. Both the lightning data and the surrenouding environment are shown using 3D graphics. Crossbow's user interface allows a user to navigate around the local area around the recording station to view lightning strikes from any viewpoint; in addition, the powerful AutoCam feature automatically navigates within the environment and adjusts the necessary viewing parameters to give the user a good angle from which to view every lightning bolt without the worry of having to find each one on his or her own. Crossbow features a "Navigator Window" that shows an overhead shot of the entire area, the current viewpoint and the current view direction, as well as indicating where the next lightning bolt will strike when not in real-time mode.
The remote scheduler program, StormTracker, allows a user to be away from the recording station and set the TREMBLE system to record lightning events in a future time frame -- much like the "timer" functionality of most VCRs. StormTracker can be accessed via a web page using the usual web browsers; data is sent and received through common CGI just like the forms seen on many corporate webpages. This handy feature of the system allows one to be miles away and still have the system record lightning bolts from a quickly-approaching or a surprise thunderstorm.
How it works: The heart of the TREMBLE system are the data acquisition and analysis subsystems. The time of a lightning flash is recorded by monitoring a lightning detector, a specially-tuned radio receiver with the capability of detecting electromagnetic pulses from either cloud to ground or cloud to cloud lightning. Once this trigger is detected, the system starts recording thunder using several (at least three) microphones. Because small segments of the lightning channel produce distinct pulses of sound, the lightning shape can be mapped to a high level of detail. The separate microphone recordings are correlated to one another and the relative delays are used to determine the bolt's direction from the recording station. The delay from the time of the lightning flash determines the distance from the recording station. Thus, each small lightning segment can be positioned in space relative to the microphone array. For more information on the algorithms used in this system see [papers by Few and Wakamatsu].
Why our system is better: While other researchers, namely Few and Wakamatsu, on whose work this system is based, have demonstrated the value of this type of system, we have taken the idea several steps further. TREMBLE provides a user-friendly interface that anyone can use without the fuss of connecting microphones or lightning detectors to their own computers and without having to know all the math. In addition, TREMBLE allows users to collect and view data remotely. Finally, a complete TREMBLE system provides the functionality of systems described in earlier work at one-tenth of the cost of those systems.
author(s): Adam Seeger,
Eric D. Baker
last update: 03 May 1999 8:31p by Eric D. Baker