Performance Analysis of Global Ionosphere/TEC Models Over Islamabad

GNSS signals are severely affected by the ionosphere layer and accurate assessment of the ionosphere delay is necessary for accurate positioning. In return, the GNSS technology may be used to estimate the total electron content (TEC) parameter in the ionosphere that can provide insight to space weather. Various organizations provide global TEC maps based on empirical data that can be used to assess the local TEC. For regions with no GNSS/GPS stations (such as for Pakistan), the GNSS users must only rely on these international models. Reliability of two such global models: International Reference Ionosphere (IRI)-2016 and Global Ionosphere Maps (GIM) by International GNSS Service (IGS), was assessed over Islamabad region. The local GPS TEC was measured for one month using a dual frequency GPS receiver installed at Islamabad as a reference. Analysis revealed that: (1) GIM overestimates the TEC whereas IRI-2016 underestimates it. In absence of local GNSS data, (2) IRI-2016 correlates better to actual TEC as compared to GIM. It was therefore concluded that in absence of local GPS –TEC, IRI-2016 is a better option to measure TEC at Islamabad.