2006 Alum

Lennox Thompson

Lennox Thompson

Years participated in RESESS:
2007 →
2008 →

An Overview

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

Academic Affiliation: Coppin State University
Science Research Mentor: Penina Axelrad, University of Colorado, Boulder


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.


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.