Evaluation of the effects of the observation weight matrix on the ambiguity resolution in LAMBDA method
Hosseini, Siavash ... [et al.]
Carrier beat phase measurements of GPS are routinely used for precise positioning applications. However, before any position can be computed, the carrier ambiguity which is an inherent part of these types of observations should be correctly resolved. Otherwise, the computed positions are biased and their corresponding accuracies are drastically decreased. Ambiguity resolution is still a challenging problem in precise positioning applications. Finding a fast and reliable method for ambiguity resolution is notwithstanding an open area of research. Precise positioning computations using carrier beat phase observations usually involve three steps: 1. resolving ambiguities as float numbers, 2. assigning integer numbers to the resolved ambiguities (fixing ambiguities), and 3. testing the fixed ambiguities and computing accurate positions. Researchers have introduced many different methods to resolve the ambiguities. However, LAMBDA (Least square AMBiguity Decorrelation Adjustment) is one of the most powerful ones used so far. This paper discusses the effects of observation weight matrix on ambiguity resolution using LAMBDA method. Numerical results show that observation weight matrix has a direct effect on the accuracy of resolved float ambiguities. Moreover, in the process of fixing ambiguities using LAMBDA method, observation weight matrix determines the dimension of search space but it has no direct effect on fixing the ambiguities. Last but not least, it is shown that the result of adjustment using fixed ambiguities has not been much affected with the quality of the observation weight matrix unless it is unreasonably wrong.
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