Variation of Total Electron Content [TEC] and Their Effect on GNSS over Akure, Nigeria

Rufus Sola Fayose,Keith Groves,Olakunle Oladosu,Rabiu Babatunde

doi:10.5539/apr.v4n2p105

Abstract

The effect of Space weather is usually linked to disturbances in the ionosphere (gradients in the Total electron content (TEC)). This has signi?cant effect especially for GPS users causing degradation in range measurements, loss of lock by the receiver of the GPS signal. Knowledge of these TEC gradients is important to various GPS users. When a GPS signal encounters large gradients in TEC, the ionospheric error in the range measurement is difficult to model and therefore eliminated (for single frequency GPS users) or, in the case of differential GPS, cannot be canceled out. For differential GPS (DGPS) or real time kinematic (RTK) users, differences over the baseline as small as 2 TEC units, where one TEC unit is 10¹6 electrons/m2, can be problematic in resolving ambiguities. Though quite a lot has been done in the developed nations in this respect, there is a dearth of such information for the developing region. This paper therefore presents the variation of total electron content (TEC) over a tropical in at Akure, Nigeria (7.15ºN, 5.12ºE) using GPS data collected over a period of one year. The data was analyzed using the GPS-TEC analysis application software provided by Institute of scienti?c research, Boston College, USA. Result obtained shows signi?cant daily and seasonal variation TEC gradients in the region.

Highlights

The ionosphere is the ionized component of the atmosphere comprising free electrons and positive ions, generally in equal numbers, in a medium that is electrically neutral (Hunsucker and Hargreaves, 1995; Baumjohann, 1999)
This paper presents the variation of total electron content (TEC) over a tropical in at Akure, Nigeria (7.15oN, 5.12oE) using GPS data collected over a period of one year
The highest TEC values in the world occur at the www.ccsenet.org/apr equatorial anomaly (EA) peaks located at approximately 15o either side of the magnetic equator (Ezquer et al, 2004)

Summary

Introduction

The ionosphere is the ionized component of the atmosphere comprising free electrons and positive ions, generally in equal numbers, in a medium that is electrically neutral (Hunsucker and Hargreaves, 1995; Baumjohann, 1999). The total electron content (TEC) provides an overall description of the ionization in the ionosphere, and it is one of the most important ionospheric quantities for various practical applications It is defined as the number of free electrons in a column of 1m2 cross section extending from the ground to the top of the ionosphere, it is a parameter of great importance for systems which use trans-ionospheric radio waves. The Total Electron Content (TEC) can be estimated by using dual frequency GPS observations, an important parameter for characterizing the ionosphere and driving data assimilative models. The Slant Total Electron Content (STEC) is the measure of the total number of free electrons in a column of the unit cross section along the path of the electromagnetic wave between the satellite and the receiver. Rama Rao et al (2006) observed that the IPP (Ionospheric Pierce Point) altitude of 350 km is valid for the satellite elevation angle greater than 50°

Data Used

Result & Discussion

Conclusion