  Autonomous helicopter landing is a challenging task that requires precise
information about the aircraft states regarding the helicopters position,
attitude, as well as position of the helipad. To this end, we propose a
solution that fuses data from an Inertial Measurement Unit (IMU) and a
monocular camera which is capable of detecting helipads position in the image
plane. The algorithm utilises manifold based nonlinear optimisation over
preintegrated IMU measurements and reprojection error in temporally uniformly
distributed keyframes, exhibiting good performance in terms of accuracy and
being computationally feasible. Our contributions of this paper are the formal
address of the landmarks Jacobian expressions and the adaptation of equality
constrained Gauss-Newton method to this specific problem. Numerical simulations
on MATLAB/Simulink confirm the validity of given claims.
