This thesis addresses the problem of autonomous precision approaching and landing of a small quadrotor UAV on a moving ground vehicle using only onboard monocular vision. A nested ArUco fiducial marker target is designed to guarantee detection from cruise altitude down to the final centimetres of the descent. The relative position and velocity of the target are estimated by a linear Kalman filter operating in the image plane, and a gain-scheduled PID controller with spatial feed-forward compensation generates body-frame velocity commands that are injected into the PX4 autopilot via MAVSDK onboard mode. The system is validated both in Gazebo Harmonic Software-In-The-Loop simulation and in outdoor experiments with a Holybro x500 V2 quadrotor landing on a Husky rover moving at up to 1 km/h..