Techniques for attitude determination using GNSS carrier phase observations

Global Navigation Satellite Systems(GNSS) are the cornerstone and main information supplier for PNT (Positioning, Navigation and Timing ) information. With the growing interest towards autonomous vehicles, it is of great importance to guarantee the accuracy and reliability of navigation estimates provided by GNSS. Other than providing the absolute localization and timing, GNSS signals can be used to compute the orientation of a platform when multiple antennas are used. Attitude determination is the process of estimating the orientation of a rigid body with respect to its environment and it constitutes a fundamental task for the navigation of spacecraft and other vehicles of large inertia. GNSS represents an appealing alternative for attitude determination. Employing a setup of multiple GNSS antennas rigidly mounted on a vehicle, one seeks to find the rotation which relates the local and global navigation frames. Accurate attitude estimation based on GNSS requires the use of GNSS carrier phase observations. In depth examination on the direct estimation of the attitude has not been yet addressed. Among the wide variety of attitude parametrizations, quaternion rotation has become the standard and most widely applied rotation characterization for robotic or computer vision applications. This knowledge or expertise has not been fully exploited for navigation purposes, or at least for GNSS carrier phase-based attitude determination. This work explores the possibilities of this approach and investigates how the Ambiguity Resolution procedure can be enriched with a constrained attitude problem already during the phase of float estimation.