Investigation on the Impact of Tropospheric Delay on GPS Height Variation near the Equator

Joseph D Dodo
Mohd Hafiz Yahya
Nor bin Kamarudin


One of the major problems currently facing
satellite-based positioning is the atmospheric refraction of
the GPS signal caused by the troposphere. The
tropospheric effect is much more pronounced at the
equatorial region due to its hot and wet conditions. This
affects the GPS signal due to the variability of the
refractive index, which in turn affects the positional
accuracy, especially in the height components. This paper
presents a study conducted in the Southern Peninsular
Malaysia located at the equatorial region, to investigate
the impact of tropospheric delay on GPS height variation.
Four campaigns were launched with each campaign
lasting for three days. The Malaysian real-time kinematic
GPS network (MyRTKnet) reference stations in Johor
Bahru were used. GPS RINEX data from these stations
were integrated with ground meteorological data observed
concurrently from a GPS station located at the Universiti
Teknologi Malaysia (UTM), at varying antenna heights for
each session of observation. A developed computer
program called TROPO.exe based on the Saastamoinen
tropospheric delay model was used in estimating the
amount of tropospheric delay. The result reveals that,
there is inconsistency in the delay variation, reaching
maximum delay of 18 m in pseudo-range measurement.
The height component shows variations with a maximum
value of 119.100 cm and a minimum value of 37.990 cm.
The result of the simulated data shows 5.00 m of
differences in height gives an effect or improvement of 1.3
mm in signal propagation. This indicates that,
tropospheric delay decreases with increase in antenna


height component, meteorological data, MyRTKnet, Saastamoinen model, signal propagation, MyRTKnet, Saastamoinen model, signal propagation, MyRTKnet, Saastamoinen model, signal propagation,

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