Improving ionospheric forecasting using statistical method for accurate GPS positioning over Malaysia

Total Electron Content (TEC) is the main parameter in the ionosphere that has significant effect on the propagation of radio waves causing delay errors on the GPS signals. Therefore, identifying an effective forecasting method is important to reduce the GPS position error. This research aimed to use the statistical Holt-Winter method to forecast the ionospheric vertical TEC (VTEC) over Malaysia. The data were derived from the Department of Survey and Mapping Malaysia (DSMM) dual frequency GPS receiver located in three stations over Malaysia, namely the Kedah station at geographic coordinates of 6.46°N-100.50°E and geomagnetic coordinates of 3.32°S-172.99°E, Johor station (south of Peninsular Malaysia) at geographic coordinates of 1.36°N-104.10°E and geomagnetic coordinates of 8.43°S-176.53°E, and Terengganu station at geographic coordinates of 4.62°N-103.21°E and geomagnetic coordinates of 5.64°N-174.98°E, during March of 2013. Based on the result, the peak of the ionospheric delay for the diurnal hourly variation was at 17:00 LT, while the minimum was from 6:00-7:00 LT. There was no significant difference in the VTEC trend among the three stations. The Holt-Winter method provided an accurate forecast during the quiet and disturbed period. The maximum MAPE was 4.5% during the quiet day and 9.1% during the disturbed day.