Research into how Global Navigation Satellite Systems (GNSS) will allow surveyors to produce more accurate and reliable measurements in less time and dual-polarisation measurements can improve scientific applications of multipath sensing.
Global Navigation Satellite Systems (GNSS) technology has become ubiquitous in navigation, surveying, and science, and its importance and influence continues to grow. GNSS technology is being continuously improved: new hardware and software aim at improving productivity, robustness, reliability, availability, precision, and accuracy. In order to deal with all these aspects of measurement quality a good understanding of potential errors is essential.
Multipath (MP), the effect of GNSS signal distortion by mixing with indirect (reflected or scattered) signals, is the most important yet currently unmodelled error source in precise GNSS. Errors caused by multipath reduce reliability, precision, and accuracy of measurements in all of applications of GNSS, including high precision surveying and scientific observations.
The research looks at a strategy of multipath mitigation by tracking and analysing both the valuable direct, and undesired multipath components of GNSS signals separately, by using a dual-polarisation GNSS antenna. While observations of right-hand polarised (direct) signals lead to the solution of positioning problem, left-hand polarised signals carry information about indirect (reflected or scattered) signals, that can reduce availability, reliability, accuracy, and precision of surveying.
An experiment was conducted involving tracking dual-polarisation data at two locations, with relatively mild and severe multipath environments respectively. Data were processed in a traditional way and using the proposed reweighting strategy. The quality of the results after reweighting increased significantly.
The results of the research should enable GNSS equipment manufacturers to develop enhanced hardware, i.e. dual polarisation antennas, together with enhanced receiver firmware and processing algorithms at minimal extra cost as the receiver hardware would not need to change significantly.
Potential beneficiaries of the dual-polarisation surveying equipment and algorithms stemming from the present research include all surveyors, who will be able to produce more accurate and reliable measurements in less time, especially in harsh MP conditions such as urban environments where effective measurement is sometimes impossible with current technology.
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