Methods for improving GPS altitude measurements and their role in monitoring the movement of high voltage transmission lines
Date
1997
Authors
Shafer, Matthew Stanton
Major Professor
Advisor
Weber, Robert J.
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Abstract
The Global Positioning System (GPS) has quickly become an important tool for nonmilitary applications such as surveying and navigation. Many new applications for this technology are still under consideration. One such application is found within the electric power industry. This paper demonstrates that GPS may be an effective tool for monitoring the movement of high-voltage transmission lines. More specifically, this thesis will focus on the problem of line sag. Line sag results from the expansion of high-voltage power lines under heavy load conditions. A series of tests were made using two GPS receivers to study the characteristics of a single GPS as well as a differential GPS (DGPS) system. Altitude accuracy was examined in detail. Single GPS results show altitude errors of more than 100 meters.
DGPS results show great improvement with sample standard deviations ranging from 5 to 20 meters. Further analysis was performed in an attempt to reduce error in the DGPS results. Averaging techniques were applied to improve the altitude accuracy using longer sample periods. Periodic and moving average techniques were chosen based on the slow nature of transmission line movement. Moving average filters yielded the best results. A vertical error probable (VEP) of 3.3% was obtained for an altitude error of 2 meters or less using a moving average filter with a time window of 30 minutes. Therefore, this technique may allow us to view a line sag of 2 meters or more 96.7% of the time.
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thesis