A Combined Filter for GPS-Based Attitude and Baseline Estimation

Ward, Lisa M.; Axelrad, Penina

doi:10.1002/j.2161-4296.1997.tb02343.x

Cited by 21 publications

(11 citation statements)

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“…Note that the line bias is assumed to have been obtained by an additional procedure [13], and so it is not considered and will be neglected in the following derivation in this investigation. Technical treatment of the line bias can be found in [14].…”

Section: The Integer Ambiguity Search Principlementioning

confidence: 99%

Improved Knight Method Based on Narrowed Search Space for Instantaneous GPS Attitude Determination

Zhang

Grenfell

2005

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ABSTRACT:The Knight algorithm can instantaneously resolve integer ambiguities and improve significantly the search speed by skipping over most less-likely integer ambiguity candidates. However, its reliability relies on the volume of the integer ambiguity search space.Utilizing coarse attitude knowledge can reduce the size of the search space. This paper proposes a new method to narrow the search space by taking into account a geometric constraint of visible satellites. The constraint is formulated as a recursive procedure and is thus very suitable to be incorporated into the search loop of the Knight method. Experimental results demonstrate that the proposed method can improve the search efficiency and reliability of the Knight method.

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Section: The Integer Ambiguity Search Principlementioning

confidence: 99%

Improved Knight Method Based on Narrowed Search Space for Instantaneous GPS Attitude Determination

Zhang

Grenfell

2005

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“…Another method is that the line biases are treated as components of the state vector of the system, and therefore, estimated along with other state components (e.g. Ward and Axelrad 1996;Purivigraipong et al 1999). A GPS receiver can measure only the fractional part of the carrier phase.…”

Section: Introductionmentioning

confidence: 99%

“…Cohen 1996;Crassidis and Markley 1997;Bar-Itzhach et al 1998;Li et al 2002) and (2) stochastic filtering algorithms (e.g. Ward and Axelrad 1996;Chun and Park 2001;Choukroun 2002). There are two types of point estimation algorithms.…”

Section: Introductionmentioning

confidence: 99%

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

Zhang

Roberts

et al. 2004

GPS Solutions

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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.

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“…A different mitigation technique, based on the assumption of low dynamics, is presented in [9]. In [9], the multipath interference effect on the attitude measurements is modeled by a sum of sinusoids.A different approach to the problem is presented in [10], where the multipath plus thermal noise is modeled as a first-order Gauss-Markov process. This statistical model is suitable for applying a Kalman filter [11].…”

mentioning

confidence: 99%

“…This statistical model is suitable for applying a Kalman filter [11]. Both methods [9,10] assume that the multipath model order is known a priori.Recently, a new method for calibrating multipath interference for a GPS-based attitude determination system was proposed [12]. This method, known as the Sky Map Method, shows improvement in and is especially suitable for a satellite in orbit.…”

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confidence: 99%

Multipath Interference Order Selection and Mitigation in GPS-Based Attitude Determination Systems

Scheim

2003

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INTRODUCTIONAttitude determination systems are important in many fields, such as land static measurements (geodesy) and mobile applications, as well as in satellites for communications. While attitude finding was traditionally based on inertial navigation systems (INS), in the last decades several navigation equipment manufacturers have developed GPS-based solutions for the problem of orientation finding. GPS-based attitude determination systems have been tested for land, marine, air, and space vehicles [1 -4]. These systems have succeeded in providing comparatively low-cost and highly stable solutions.Multipath effects on GPS receivers for positioning applications, such as geodesy, are investigated and reported in [5]. A geometrical model is presented and applied to reduce the multipath interference in a static receiver utilizing multiple antennas [6].It is well known that the accuracy of a GPS-based attitude determination system is considerably limited by multipath interference [7 -10]. A GPS-based attitude determination system is basically a differential phase measurement apparatus. Multipath affects the receiver operation when a few delayed echoes of the desired signal are received and combined with the desired signal. The signal mixture induces phase error, which results in turn in large navigation errors.A method for calibrating multipath interference is presented in [8]. The method of [8] is based on an approximation of the multipath interference using a sum of spherical harmonic functions. A different mitigation technique, based on the assumption of low dynamics, is presented in [9]. In [9], the multipath interference effect on the attitude measurements is modeled by a sum of sinusoids.A different approach to the problem is presented in [10], where the multipath plus thermal noise is modeled as a first-order Gauss-Markov process. This statistical model is suitable for applying a Kalman filter [11]. Both methods [9,10] assume that the multipath model order is known a priori.Recently, a new method for calibrating multipath interference for a GPS-based attitude determination system was proposed [12]. This method, known as the Sky Map Method, shows improvement in and is especially suitable for a satellite in orbit. This is due to a relatively static environment surrounding the receiver antenna array. In this case, the platform often experience a periodic dynamics, which makes the problem setting similar to a static scenario.A new postprocessing iterative algorithm for multipath interference mitigation is presented in this paper. The proposed algorithm is based on separation of the measured attitude into time sections where the multipath interference acts uniformly.

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A Combined Filter for GPS-Based Attitude and Baseline Estimation

Cited by 21 publications

References 1 publication

Improved Knight Method Based on Narrowed Search Space for Instantaneous GPS Attitude Determination

Improved Knight Method Based on Narrowed Search Space for Instantaneous GPS Attitude Determination

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

Multipath Interference Order Selection and Mitigation in GPS-Based Attitude Determination Systems

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