ABSTRACT
GPS is the only fully-operational satellite-based positioning system currently available to all-inclusive
users at no direct charge. Triggered by the value-added functionality and the innovative field operation
interoperability brought by satellite positioning and navigation systems, GPS has been widely used by
professionals and practitioners to address diverse applications such as navigation, surveying, mapping
and engineering purposes. GPS utilizes the time-of-arrival (TOA) ranging concept based on the satelliteto-receiver signal transmission to determine one position. Apparently, the key limitations currently
facing this multi-satellites system is the latency of signal arrival caused by the effect of troposphere
where most of the world's weather takes place. The effect is much more pronounced in Malaysia as it is
located at the equatorial region where the troposphere extends the most above the earth surface in
comparison to any other region. High humidity climate caused by the spatial and temporal variability of
water vapour content within the troposphere exaggerates the signal propagation effect even further
thus affecting the accuracy of GPS derived positions. Result shows that by neglecting the use of
tropospheric a priori model, maximum residuals in Easting, Northing and Height components due to
tropospheric effect are 68.880 cm, 68.970 cm and 119.100 cm respectively. Similarly, reaching to the
minimum and maximum RMS value of 16.8 and 29.2 respectively, GPS Height component is by far the
most affected component compared to the Horizontal components. In most cases, the result also
reveals that tropospheric error is a distance dependant error that increases with the increases in the
baseline length between two stations.