scholarly journals Attitude determination from single-antenna carrier-phase measurements

2002 ◽  
Vol 91 (7) ◽  
pp. 4677-4684 ◽  
Author(s):  
Thomas B. Bahder
Keyword(s):  
Carrier Phase ◽  
Attitude Determination ◽  
Phase Measurements ◽  
Single Antenna

scholarly journals Analysis of Attitude Determination Methods Using GPS Carrier Phase Measurements

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Leandro Baroni ◽  
Hélio Koiti Kuga
Keyword(s):  
Carrier Phase ◽  
Attitude Determination ◽  
Precise Determination ◽  
Integer Ambiguity ◽  
Integer Number ◽  
Method Performance ◽  
Phase Measurements ◽  
Double Differences ◽  
Number Of Cycles

If three or more GPS antennas are mounted properly on a platform and differences of GPS signals measurements are collected simultaneously, the baselines vectors between antennas can be determined and the platform orientation defined by these vectors can be calculated. Thus, the prerequisite for attitude determination technique based on GPS is to calculate baselines between antennas to millimeter level of accuracy. For accurate attitude solutions to be attained, carrier phase double differences are used as main type of measurements. The use of carrier phase measurements leads to the problem of precise determination of the ambiguous integer number of cycles in the initial carrier phase (integer ambiguity). In this work two algorithms (LSAST and LAMBDA) were implemented and tested for ambiguity resolution allowing accurate real-time attitude determination using measurements given by GPS receivers in coupled form. Platform orientation was obtained using quaternions formulation, and the results showed that LSAST method performance is similar to LAMBDA as far as the number of epochs which are necessary to resolve ambiguities is concerned, but with processing time significantly higher. The final result accuracy was similar for both methods, better than 0.1° to 0.2°, when baselines are considered in decoupled form.

scholarly journals Analytical and Iterative Solutions to GNSS Attitude Determination Problem in Measurement Domain

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Baowei Chen ◽  
Guobin Chang ◽  
Shengquan Li ◽  
Kailiang Deng
Keyword(s):  
Least Squares ◽  
Carrier Phase ◽  
Attitude Determination ◽  
Estimation Error ◽  
Direction Cosine ◽  
Initial Guess ◽  
Frobenius Norm ◽  
Phase Measurements ◽  
Least Squares Estimate ◽  
Gibbs Vector

Attitude determination using double-differenced GNSS carrier phase measurements is studied. A realistic stochastic model is employed to take the correlations among the double-differenced measurements into full consideration. Two important issues concerning iteratively solving the nonlinear least-squares attitude determination problem are treated, namely, the initial guess and the iteration scheme. An analytical and sub-optimal solution is employed to provide the initial guess. In this solution, the orthogonal and determinant constraints among the elements of the direction cosine matrix (DCM) of the attitude are firstly ignored, and hence a relaxed 3×3 matrix is estimated using the linear weighted least-squares method. Then a mathematically feasible DCM, i.e., orthogonal and with +1 determinant, is extracted from the relaxed matrix estimate, optimally in the sense of minimum Frobenius norm. This analytical initial guess estimation method can be used for all feasible cases, including some generated ones, e.g., the case with only 3 antennas and only 3 satellites, subject possibly to some necessary, yet minor modifications. In each iteration, an error attitude, whose DCM is parameterized using the Gibbs vector, is introduced to relate the previously estimated and the true DCM. By linearizing the measurement model at the zero Gibbs vector, the least-squares estimate of the Gibbs vector is obtained and then used to correct the previously estimated DCM. By repeating this process, the truly least-squares estimate of the attitude can be achieved progressively. These are in fact Gauss-Newton iterations. For the final estimate, the variance covariance matrix (VCM) of the attitude estimation error can be retained to evaluate or predict the estimation accuracy. The extraction of the widely used roll-pitch-yaw angles and the VCM of their additive estimation errors from the final solution is also presented. Numerical experiments are conducted to check the performance of the developed theory. For the case with 3 2-meter long and orthogonally mounted baselines, 5 visible satellites, and 5-millimeter standard deviations of the carrier phase measurements, the root mean squared errors (RMSE) of the roll-pitch-yaw angles in the analytical solution are well below 0.5 degrees, and the estimates converge after only one iteration, with all three RMSEs below 0.2 degrees.

Development of an Integrated Low-Cost GPS/Rate Gyro System for Attitude Determination

2004 ◽  
Vol 57 (1) ◽  
pp. 85-101 ◽  
Author(s):  
Chaochao Wang ◽  
Gérard Lachapelle ◽  
M. Elizabeth Cannon
Keyword(s):  
Carrier Phase ◽  
Measurement Errors ◽  
Attitude Determination ◽  
Low Cost ◽  
Angular Rate ◽  
Integrated System ◽  
Cycle Slip ◽  
Gps Receivers ◽  
Phase Measurements ◽  
Rate Gyro

The use of low-cost GPS receivers and antennas for attitude determination can significantly reduce the overall hardware system cost. Compared to the use of high performance GPS receivers, the carrier phase measurements from low-cost equipment are subject to additional carrier phase measurement errors, such as multipath, antenna phase centre variation and noise. These error sources, together with more frequent cycle slip occurrences, severely deteriorate attitude determination availability, reliability and accuracy performance. This paper presents the investigation of a low-cost GPS/gyro integration system for attitude determination. By employing the dead reckoning sensor type, the ambiguity search region can be specifically defined as a small cube to enhance the ambiguity resolution process. A Kalman filter is implemented to fuse the rate gyro data with GPS carrier phase measurements. The quality control system based on innovation sequences is used to identify cycle slip occurrences and incorrect inter-antenna vector solutions. The availability of the integrated system also improves with respect to the GPS standalone system since the attitude parameters can be estimated using the angular rate measurements from rate gyros during GPS outages. The low-cost hardware used to design and test the integrated system consists of CMC Allstar receivers with the OEM AT575-70 antennas and Murata ENV-05D-52 piezoelectric vibrating rate gyroscopes. Tests in the urban area demonstrated that the introduction of rate gyros in a GPS-based attitude determination system not only effectively decreased the noise level in the estimated attitude parameters but coasted the attitude output during GPS outages and also significantly improved the system reliability.

Survey Boat Attitude Determination with GPS/IMU Systems

2001 ◽  
Vol 54 (1) ◽  
pp. 135-144 ◽  
Author(s):  
Reha Metin Alkan ◽  
Orhan Baykal
Keyword(s):  
Carrier Phase ◽  
Inertial Measurement Unit ◽  
Attitude Determination ◽  
Measurement Unit ◽  
Phase Measurements ◽  
Inertial Measurement ◽  
The Third ◽  
Hydrographic Surveying ◽  
Echo Sounder

Any vehicle such as a vessel or aeroplane has three attitude parameters. These are most commonly defined as pitch, roll and heading from true north. In hydrographic surveying, determination of these parameters is essential for the correction of multi-beam echo sounder measurements. In the study on which this paper is based, two of the three parameters, the pitch and roll angles, were measured with an inexpensive IMU (Inertial Measurement Unit) device. The third was calculated from GPS carrier phase measurements that were collected from two antennas on the boat. The GPS antennas depart from the vertical when they are subject to pitch and roll effects. In this case, the coordinates derived from GPS will be erroneous. Thus, if heading is to be calculated accurately, the horizontal coordinates have to be corrected for pitch and roll. This paper defines an algorithm for the purpose that enables pitch and roll angles to be measured with an accuracy of about 0·003 arcdeg and headings computed with an accuracy of about 0·010 arcdeg.

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