Today, GNSS (Global Navigation Satellite Systems) is a widely spread technology and are used in many different ways. GNSS is the collective name for American GPS, Russian Glonass and European Galileo and some other smaller navigation systems. When surveying with GNSS technology, there are many things that can affect the accuracy of the measurements.
In this thesis the focus is on how these measurements are being effected by disturbances in the ionosphere. The conditions in the ionosphere are largely affected by the amount of solar activities. A guideline for the amount of solar activity is to monitoring the sunspot numbers and the solar cycle.
With more radiation occurring at radio frequencies as well as in the UV-region with more sunspots. The resulting free electrons influence the GNSS signals as they propagate through the ionosphere and the ionized gases cause the phase of the GNSS signal to shift and slows down the speed of the signal.
By processing data from three SWEPOS stations forming one shorter and one longer baseline, the estimated errors for the measurements are being calculated for different conditions in the ionosphere. The focus in this thesis is at the accuracy and precision of those measurements. To capture different ionospheric conditions, a few days from different parts of the solar cycle are chosen as representation for these different conditions.
For each day different times of day and different length of measuring sessions are being calculated. All the calculations of the baselines are carried out in Trimble Business Center, and the results are presented in charts for each day and some key measurements are presented for the whole studied period.
The result gives no clear correlation between the number of sunspots and the accuracy and precision of the GNSS measurements, and it is not possible from the result to see that a particular time of the day is better suited for executing GNSS surveying.
From the studied material and the result of this thesis it is hard to see any dependency between the solar activity and the accuracy on GNSS measurements. It is not possible from the result see any connection between the length of the measuring time and the outcome of the measurement, as it is often no clear pattern stating that a longer measuring time would give better measurement.
The results differ in many ways from other reports on this subject and the result are so totally different that something seems to not be right in this report. If a correlation analysis had been performed instead of just an ocular examination, it had probably given a more satisfying result of the studied material.
The result of this thesis is in many ways on collision course with other similar report on this subject and therefore the results in this report can be neglected and rejected in favor of the result of this other more scientific reports.
Source: KTH
Authors: Hansson, Anton