Advantages
Precise point position has been defined as a method used to establish the accurate position by the aid of global positioning system (Ovstedal, 2002). One major advantage of precise GNSS or GPS is that the application results to tremendous cutting down of coasts in terms of labour and equipment. Similarly logistics for operations are also minimized because the system does not need the services of ground based stations.
The cutting of costs has seen to it that the money saved can be used to improve the technology. Additionally, it is worth remembering that using the technology has helped engineers have data that are less erroneous. This is because precise positioning using GNSS and GPS is capable of estimating the receiver clock as well as the atmospheric and tropospheric effects attributes as well as the parameters for geographic coordinates.
For this reason it offers another way of providing users with accurate time transfer that can be used to establish water vapour by use of the receiver. The data with high degree of accuracy are applicable in airborne mapping, engineering among others.
According to Zumberge, et. al., 1998 another benefit of the technology is that it only involves one GPS receiver therefore users are not compelled to construct a ground local base station. With this regards, it thus removes the ‘spatial operating range limit’ and the problem of simultaneously observing both the rovers as well as local base receivers.
On the lime line of reasoning, GNSS and GPS have been viewed as global positioning technique since the ultimate results are termed as a global reference frame. For that matter it offers users with a higher degree of consistency.
It is worth noting that precise GNSS/GPS position and application brings with it the advantage of high degree of reliability. Although a single receiver is used, the increased redundancy of data collected usually helps in establishing wrong measurements.
Similarly there is improved geometry as well as convergence time. Lastly the technology has dual frequency observation which helps in coming up with ionosphere-free linear combination of original observations thus doing away with the effects of ionosphere (Ovstedal, 2002).
Disadvantages
It has been noted with concern that when dealing with indifference observation in precise GNSS/GPS positioning there is no possibility of correcting the carrier phase ambiguities. This means that these ambiguities need to be always approximated in what is referred to as float solution (Leandro & Santos, 2006).
It is worth remembering that the initialization time of about 20 minutes need for the float position to be converged into centimetre accuracy has led to a limited application of GNSS/GPS data in applications that require real time data.
As suggested by Niell, 1996 another problem with precise GNSS/GPS positioning is that the coordinates generated are usually in the same global reference frame as that of the sending satellite.
Considering the fact that the user might need to change the coordinates into either local or regional frames so that it can be applicable to various mapping application; the process of transformation is quite challenging and might result to serious errors if the user is not careful.
It is also with mentioning that the technique calls for unconventional corrections aimed at mitigating systematic errors which affects centimetre accuracy. Issues addressed include offset of the satellite antenna, site displacement effects among others. Due to the fact that the corrections are irregular, data generated by two individuals might be different (Kouba & Heroux, 2001).
References
Kouba, J. & Heroux, P., 2001. GPS Precise Point Positioning Using IGS Orbit Products, GPS Solutions, vol.5, no.2, pp. 12-28.
Leandro, F. & Santos, M., 2006. Wide area based precise point positioning. Proceedings of ION GNSS 2006, 26–29 September 2006. Fort Worth, Texas, pp. 2272–2278.
Niell, A., 1996. Global mapping functions for the atmosphere delay at radio wavelengths. J Geophys Res, vol. 101, no. B2, pp. 3227–3246.
Ovstedal, O., 2002. Absolute Positioning with Single Frequency GPS Receivers, GPS Solutions, vol.5, no.4, pp. 33-44.
Zumberge, J., Heflin, M., Jefferson, C., Watkins, M. & Webb, F., 1998. Precise Point Positioning for the efficient and robust analysis of GPS data from large networks, J. Geophysical Research, vol.102, no. B3, pp. 5005-5017.