Finding the correct integers is the key to high precision range measurements. This has been an issue of investigation since the early 1980’s and many different techniques have been developed, none of them can guarantee to resolve the correct integers in 100% of the cases though. This study focuses on a new approach for Integer Ambiguity Resolution (IAR), using a geometric approach and Interval Analysis (IA).
The new method can guarantee that if all measurement errors are bounded by the interval bands the correct integers will always be found. Depending on the width of the interval bands though, there may be more than one solution. The research objective of the thesis is to determine if the Interval Based Integer Am-biguity Resolution (IBIAR) method can be used for accurate attitude determination with only one remaining (correct) solution.
Earlier results using the Bounded integer ambiguity resolution using interval analysis (BOUNDS) algorithm (van Kampen, 2010) have shown that one solution can not be obtained for all epochs when applied to flight data from a Cessna Citation II research airplane equipped with three antennas. The analysis did not make use of two frequencies, comparing the baseline orientations and adding an extra antenna though. These aspects are added to the BOUNDS algorithm in order to potentially reduce the number of solutions. Further the effects of the noise on both the carrier phase measurements and baseline lengths are investigated.
All simulations are done off line as no real flight data is available for the test configurations. The simulations are loosely based on the Cessna Citation II research airplane belonging to the Dutch National Aerospace Laboratory (NLR) and Delft University of Technology (DUT). For all simulations the correct solution is bounded by the noise levels, which means that the BOUNDS algorithm theoretically always finds the correct solution. Further it is assumed that there are no multipath effects, no restrictions on the attitude angles the airplane can fly with, that the antennas always have a clear view of the satellites and the cut off angle is zero degrees.
The conclusion of the study is that the IBIAR method can be used for attitude determination where one (correct) solution remains but the accuracy of the solution is low. The study gives recommendations on how to improve the accuracy of the attitude angles.
Source: KTH
Author: Zemovski, Mikael
