  A main problem in autonomous vehicles in general, and in \acp{UAV} in
particular, is the determination of the attitude angles. A novel method to
estimate these angles using off-the-shelf components is presented. This paper
introduces an \ac{AHRS} based on the \ac{UKF} using the \ac{TRIAD} algorithm as
the observation model. The performance of the method is assessed through
simulations and compared to an \ac{AHRS} based on the \ac{EKF}. The paper
presents field experiment results using a real fixed-wing \ac{UAV}. The results
show good real-time performance with low computational cost in a
microcontroller.
