Section I Preliminaries on Attitude Representations and Rotations. What Are Quaternions and Why Haven\u2019t I Heard of Them? Rotation in 3D Space. Attitude Parametrization, Kinematics, and Dynamics. Section II Multisensor Filtering for Attitude Estimation: Theories and Applications. Stable Estimation of Rigid Body Motion Based on the Lagrange\u2013d\u2019Alembert Principle. The Additive and Multiplicative Approaches to Quaternion Kalman Filtering. Spacecraft Attitude Determination. How to Deal with the External Acceleration When Estimating the Attitude Using Inertial Measurement Units: A Linear Kalman-Based Filtering Approach. From Attitude Estimation to Pose Estimation Using Dual Quaternions. Distributed Estimation for Spatial Rigid Motion Based on Dual Quaternions. A Quaternion Orientation from Earth Field Observations Using the Algebraic Quaternion Algorithm: Analysis and Applications in Fusion Algorithms. Recent Nonlinear Attitude Estimation Algorithms. Low Complexity Sensor Fus.