说明：  采用卡尔曼滤波器对系统的俯仰角、 滚转角和航向角的误差进行最优估计；设计数据融合的判别准则，并根据判据的判断结果调整卡尔曼 滤波器中的量测信息，使系统可用于小型无人机的定高自主飞行
(Kalman filter system pitch angle, roll angle and yaw angle error optimal estimation design data fusion criterion, and adjust according to the criterion of judging the results of measurement in the Kalman filter, making the system set high for small UAVs autonomous flight)