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Mathematical Problems in Engineering
Volume 2012 (2012), Article ID 596396, 10 pages
http://dx.doi.org/10.1155/2012/596396
Research Article

Analysis of Attitude Determination Methods Using GPS Carrier Phase Measurements

1Institute of Science, Engineering and Technology, Federal University of Jequitinhonha and Mucuri Valleys (UFVJM), Rua do Cruzeiro, 1, 39803-371 Teófilo Otoni, MG, Brazil
2Space Mechanics and Control Division (DMC), National Institute for Space Research (INPE), 12227-010 São José dos Campos, SP, Brazil

Received 15 November 2011; Accepted 19 January 2012

Academic Editor: Silvia Maria Giuliatti Winter

Copyright © 2012 Leandro Baroni and Hélio Koiti Kuga. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

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.