High-sensitivity GNSS: The trade-off between availability and accuracy

Abstract

Abstract: High-sensitivity (HS) GPS receivers can acquire and track signals 20–25 dB below the threshold of a conventional receiver. This allows GPS positioning in environments where other receivers might not provide enough observations. There are also applications like GIS data collection, mapping, or traffic guidance and control, where both types of receivers might be applicable, and the question is which one is the better choice? Using data from a dedicated experiment we show that indeed an HS receiver can provide sig-nificantly more observations than a conventional GPS receiver, because it also tracks satel-lites behind an obstruction. Here, this results in a positioning availability of nearly 100 % for the HS receiver, whereas the conventional receiver gives a controlled position solution only 50 % of the time. However, the accuracy of the observations additionally provided by the HS receiver may be a factor 10–100 worse than that of the line-of-sight observations. This differ-ence in quality needs to be taken into account properly when computing position, velocity, and time. Failure to do so may result in position errors of several hundred meters. We show that positioning accuracies of 5–20 m are attainable even in harsh environment when using an optimum variance model and a sophisticated quality control kernel in the positioning algo-rithm. These components help to balance increased availability and desired accuracy by re-ducing the influence of poor observations. Using such algorithms, there is a clear advantage of using HS receivers instead of conventional receivers in applications requiring meter level accuracies with moderate antenna dynamics. 1.