Hunegnaw, Adisu (PhD)Chanie, Asmamaw2018-06-132023-11-282018-06-132023-11-282013-04http://etd.aau.edu.et/handle/12345678/637Ionosphere is the major source of error for geodetic applications despite the fact that it’s possible to remove most of the effect using its dispersive nature. However, it’s only the first order of the ionospheric effect that can be removed using dual frequencies signal observations. The second and third order ionosphere effect cannot be removed though we can model their effects on geodetic applications such as their effects on Global Positioning System (GPS) signals. The study mainly focuses on the assessment of higher order (second and third) ionosphere effects on GPS for accurate positioning along the equatorial regions. Some stations at higher latitudes were also included in our GPS data processing for comparison purposes. GAMIT/GLOBK software was used to process the GPS data including a suite of other ancillary information. The time series of the residuals from the final GAMIT/GLOBK result were compared with the geomagnetic field effects and solar cycle (sunspot activities). High ionopheric effects on the GPS signals from stations along the equator were observed relative to stations at higher latitudes due to the fact that total electron content density is high along the equator. In addition to this, the contribution of Equatorial Electrojet (EEJ) to ionospheric disturbances is higher along the equator. Higher total electron content was also observed for the stations from the equatorial region in particular on years 2002 and 2012 as these are the years where solar activity were at maximum. Keywords: GPS, Higher order ionosphereic effects, Total electron contents density, Geomagnetic fieldenGPS; Higher Order Ionosphereic Effects;Total Electron Contents Density; Geomagnetic FieldThesis