Lennox Thompson

Years participated in RESESS: 2008, 2007, 2006

An Overview

Major: Mathematics and Computer Science

Academic Affiliation: Coppin State University


Lennox Thompson from Coppin State University in Baltimore, Maryland is a computer science and mathematics major participating in RESESS for the first time. Professor Penny Axelrad of the Department of Aerospace Engineering at University of Colorado was Lennox’s science mentor in his study on how visualizing how objects in the environment interrupt satellite signals that are transmitted to GPS antennas. This interruption causes distortion to the signal resulting in inaccurate measurements called multipath error. By using specialized software to create a detailed three-dimensional map of proposed GPS locations, people installing GPS stations can find the optimum position for the station.


2006- A new approach to Global Positioning System (GPS) multipath visualization

Multipath is a condition where the transmitted radio signal is reflected by physical features or structures, creating multiple reflections of the same signal arriving at the receiver at different times. The result is degradation in signal strength of the transmitted signal from the satellite to the Global Positioning System (GPS) antenna. Multipath occurs when transmitted signals do not go directly to the GPS antenna, but rather arrive from different parts of the environment. These additional reflected signals cause distortion of the direct signal to GPS antennas, but proper positioning can minimize multipath error. Reception of bounced signals at the antenna causes erroneous data from the GPS receiver, which results in inaccurate measurement of position. The GPS receiver has trouble distinguishing between reflected signals from direct signals and that is one of the problems multipath produces. To minimize the multipath error, positioning the GPS antenna from a location that is less susceptible to multipath can help the receiver accept amplified signals. Furthermore, a MATLAB simulation was developed previously that predicts multipath based on site analysis data to generate the plot of vectors on a Digital Terrain Model (DTM). This work produces a three-dimensional plot of ray paths when signals are being transmitted from a satellite. This ray path visualization enables a user to properly position a GPS antenna to minimize the multipath error.

2007- Displacement modeling of a volcanic magma chamber

Volcanoes can be hazardous if increased pressure in the magma chamber becomes great enough that magma is forced upward through a crack to the ground surface and erupts. The magma chamber which lies beneath a volcano is a large underground pool of molten rock lying under the surface of the earth’s crust. The problem with the magma chamber and why it is significant is because there are unknown processes occurring inside volcanoes. Researchers have not yet understood the processes occurring inside of a volcanic magma chamber. My research is to update a mathematical displacement model which describes the magma chamber properties such as depth and volume change (e.g. inflation or deflation at surface). So far, the method used to get the displacement model to work was to move all the file structures along with the displacement program in one memory storage space in order for the program to work in Matlab. As a result, the program was able to import and export data in addition to loading geographical features of the displacement model to better understand the magma chamber for the purpose of prediction of future volcanic eruptions.

2008- Seismic Investigation of the Southern Rio Grande Rift

An upwelling of basaltic magma 29 million years ago caused the earth’s crust to spread apart and create a region known today as the Rio Grande Rift (RGR). The RGR extends from central Colorado through New Mexico to northern Mexico near El Paso. The RGR has different geologic features that distinguish it from most other valleys (e.g., RGR was not cut by a river nor does a river branch upstream). A growing body of evidence shows that geologic activity still occurs in the RGR, with a continuation of faulting, seismicity, and widening at a small rate. This research focuses on the Southern Rio Grande Rift (SRGR) to develop a contour map of velocity structures and moho depth using data from seismograms that have been installed around the region. The topographic mapping, Vp/Vs ratio, and the crustal thickness of the SRGR will define the crustal structure and the tectonic evolution of the region. The results will assist in understanding the crustal structure of not only the SRGR, but the RGR in general. Results have been obtained for the SRGR using Generic Mapping Tool which includes a contour plot of the Vp/Vs ratio and crustal thickness in that region.