Methods to Estimate Magnetic Declination for an Unmanned Aerial Vehicle

Measurement of the heading free from magnetic declination using several GPS antennas is widely used, but it is not suitable for small unmanned aerial vehicles because of limited payload and body length. In this paper, we propose two methods to estimate magnetic declination. One is for UAV for 3D terrain mapping with a laser scanner. Measurements which are collected from different directions are matched to estimate magnet declination. The other uses an IMU and one GPS antenna. It consists of 1) estimation of acceleration of motion from GPS measurements and 2) estimation of magnetic declination using the estimated acceleration and IMU measurement. We show that the estimation of magnetic declination results in reduced QUEST, an eigenvalue problem of a 2 x 2 real matrix using a quaternion which expresses rotation. Experimental results of flight control of an unmanned helicopter demonstrate the effectiveness of proposed methods.