Validation of IRI-2012 and NeQuick Models Predicted TEC with GPS – India

Abstract

The Total Electron Content (TEC) is a vital and most dominant ionosphere parameter that can cause Global Positioning System (GPS) signal delays, signal degradation and in extreme cases loss of lock. This results into inefficient operations of ground and space based Global Navigation Satellite System (GNSS) applications. Ionosphere range delay on GPS signals is a major error source for GPS positioning and Navigation. Earlier research has shown that the ionosphere is highly variable at low latitude and equatorial regions. Since India located near to the equator, the gradient of equatorial ionization anomaly between the through and the crest is very sharp, which results in large variation of ionospheric electron content. In this thesis the seasonal variation of ionosphere TEC is compared for several stations (Bangalore(12.96°N, 77.5667°E), Hyderabad (17.36°N, 78.47°E), Lucknow (26.8000° N, 80.9000° E), Port Blair (11.6683° N, 92.7378°E)) in India from 2013 to 2014. The observed TEC from GPS is compared with those derived from the International Reference Ionosphere (IRI)-2012 model (IRI-NeQuick and IRI-2001). From the Results we observed that TEC achieves its highest value during the summer, moderate TEC values in the winter and minimum in equinox seasons. And also observed that as the longitude increases the TEC variability is more in the ionosphere. The study of TEC variability is, therefore useful for GNSS users in order to minimize errors where high level of accuracy in measurements is required.