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A study on the impact of GPS-derived tropospheric delay on radio propagation over some Nigerian stations

Nzeagwu Nnabuenyi Jonas, J. O. Urama, A. E. Chukwude, D. I. Okoh

Abstract


Abstract

The effect of GPS-derived tropospheric delay on radio propagation over five Nigerian stations is examined. The stations are located in the African equatorial region, and include: Abuja (8.9 oN, 7.4 oE), Akure (7.3 oN, 5.2 oE), Enugu (6.5 oN, 7.5 oE),  Lagos (6.5 oN, 3.4 oE), and Port Harcourt (4.8 oN, 7.0 oE). This is the first study in the African equatorial region that uses in-situ meteorology measurements as well as GPS satellite measurements to present the impact of tropospheric delay on radio propagation, especially with respect to varying elevation angles. Data used for the study covered the twelve-month period from January to December 2013, and the modified Hopfield model was used to derive the tropospheric delays. The results show that GPS-derived tropospheric delays vary significantly with elevation angles of the satellites. The values of the tropospheric delays are typically about 2.5 m when the radio transmission path is at around 90o of elevation, and the values increase to over 20 m when the radio transmission is at around 10o of elevation. The rate of change of the tropospheric delay (with respect to elevation angle) increases with decreasing elevation angle. The tropospheric delay typically increases by about 3% when the elevation angle changes from 90o to 80o, and by about 60% when the elevation angle changes from 20o to 10o. Time-dependent maps of the tropospheric delay reveals a pattern which indicates that variation of the tropospheric delay is significantly controlled by elevation angles of the GPS satellites.   


Keywords


Keywords: Tropospheric delay, GPS, meteorology, elevation angle, radio propagation.

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References


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