Real Time GPS Data Processing for `Sag Measurement' on a Transmission Line

A relatively new method of measuring sag on a transmission line conductor using differential global positioning system (DGPS) is discussed with focus on the real time data processing module integrated with the DGPS system. The objective of the data processing module was to extract the altitude information from GPS signals and evaluate the conductor to ground clearance in real time. Field tests indicated that using exponential smoothing with a processing window size of 60 or 120 seconds gives the most accurate value of sag measured via GPS. Measured values were in good agreement with the actual values.