This paper presents a data fusion algorithm by means of a particle filter (PF), for estimate the position of a quadrotor equipped with multiple sensors. A global positioning system (GPS) is considered for position measurement in a loosely coupled scheme, velocity can be obtained from an optic flow sensor, whilst an inertial measurement unit (IMU) can provide orientation and angular rate measurements. Simulations were carried out, where real noise from a not expensive GPS is added to the simulated position to test the proposed algorithm.