High-Order Ionospheric Effects on 3-D GPS Coordinate Estimation in Turkey

The global positioning system (GPS) can navigate and position at any time and weather conditions, but subject to a variety of error sources. The most important one of these errors is the ionospheric delay when the GPS signals propagate through the ionosphere. The first order ionospheric effects can be removed using dual frequency GPS receivers, while the higher order ionospheric (HOI) effects are much smaller than the first order effects, which are generally neglected. However, under highly active solar activities condition, high order ionospheric effects may be big and should be eliminated. In this study, the high order ionospheric effects on 3D GPS coordinate components was investigated with 30 days (June 2011) of GPS data at 8 GPS stations in Turkey. Firstly, the high order ionospheric effects were corrected in the RINEX observation file, and then raw and corrected observations were processed in GAMIT software to obtain precise coordinate components. Results show that average 10, 7 and 24 millimeters changes occurred in the north, east and up components by high-order ionospheric effects, respectively. During the peak solar activity days in 2011, it is observed that the high-order ionospheric effects in the north, east and up components can reach 18, 11 and 43 millimeters change, respectively.