On-the-fly GPS-based attitude determination using single- and double-differenced carrier phase measurements

Abstract

Carrier phase measurements are primary observations for GPS attitude determination. Although the satellite-related errors can be virtually eliminated by forming single differences, the baseline-related errors such as line biases are still present in the single-differenced carrier phase measurements. It is, therefore, difficult to resolve the single-differenced integer ambiguities due to the line biases. By forming double differences, the line biases of the single-differenced carrier phase measurements can be effectively removed. However, the main disadvantages of this method lie in the fact that the double-differenced measurements are mathematically correlated and consequently the attitude obtained from the double differences is noisy. This paper presents a new algorithm through which both single and double differences are used simultaneously to resolve these problems in realtime. The solution of the integer ambiguities can be obtained by searching for the most likely grid point in the attitude domain that is independent of the correlation with the double differences. Next, the line biases and corresponding single difference integer ambiguities can be resolved on the fly by using the noisy attitude solution obtained from the previous double difference procedure. In addition, the relationship between the physical signal path difference and the line bias is formed. A new method is also applied to derive the attitude angles through finding the optimal solution of the attitude matrix element. The proposed new procedure is validated using ground and flight tests. Results have demonstrated that the new algorithm is effective and can satisfy the requirement of real-time applications.

A constrained LAMBDA method for GPS attitude determination

“…Differenced GPS carrier phase measurements from more than two antennas and line-of-sight vectors from baseline to GPS satellites can be used to determine the attitude of the vehicle (Li et al 2004). The current algorithms for attitude determination can be roughly divided into two categories.…”

“…Because of the real-time requirement for the attitude determination, the latter category of ambiguity resolution methods is always selected (Park and Teunissen 2003;Li et al 2004). However, the search method can converge to an incorrect set of integer ambiguities due to any carrier phase noise (Teunissen 1997;Yoon and Lundberg 2002).…”

Enhancing Stand-Alone GPS Code Positioning Using Stand-Alone Double Differencing Carrier Phase Relative Positioning

“…Single differences can be formed between two receivers, two satellites, or two epochs. Double differences are formed between any two single differences, whereas triple differences are between the three forms of single differences, including two receivers, two satellites, and two epochs [2].…”

Improving the GNSS Attitude Ambiguity Success Rate with the Multivariate Constrained LAMBDA Method

“…Many works investigated the feasibility and performance of GNSS Attitude Determination, see e.g. [1][2][3][4][5][6]. The key for a precise attitude estimation is the ambiguity resolution process, since only when the integers inherent to the GNSS carrier phase observations are correctly fixed one is able to exploit the carrier phase data, which are of two orders of magnitude more accurate than the GNSS code observations.…”