Leveling Process of Total Electron Content (TEC) Using Malaysian Global Positioning System (GPS) Data

The signals from the satellites of the Navstar Global Positioning System (GPS) travel through the earth's ionosphere on their way to GPS receivers. However, ionospheric delay is one of the main sources of error in GPS. The magnitude of the ionospheric delay is influenced by the Total Electron Content (TEC) along the radio wave path from a GPS satellite to the ground receiver. This study investigates the TEC using GPS data collected from Wisma Tanah, Kuala Lumpur, KTPK (3° 10’ 15.44”N, 101° 43’ 03.35”E) station and processed and analyzed under quiet geomagnetic day at the equatorial region on 8 November 2005. This research assesses the errors translated from the code-delay to the carrier-phase ionospheric observable by the so-called leveling process, which was applied to reduce multipath from the data. It was found that the leveled carrier-phase ionosphere observable was affected by a systematic error, produced by code-delay multipath through the leveling procedure. The effects, however, do not cancel after averaging all the data. Dual frequency carrier-phase and code-delay GPS observations are combined to obtain ionospheric observable related to the slant TEC (TECs) along the satellite-receiver line of sight (los). This results in the absolute differential delay and the remaining noise was discarded. These are the first results obtained using TEC-GPS technique for TEC measurement in Malaysia.