To realize target automatic orientation, we establish the system of target automatic orientation. This system takes use of the
method of three-point-orientation, and analyses the method’s error. Base on the model of earth ellipse reference space target
orientation, this method use the position information of plane at different time and the distance of the target between the
aircraft to establish the math model of the method of three-point-orientation. At the same time, we get the target’s position
information through the exact math resolve. At last, we analyses the method’s error. The result shows the system using the
method of three-point-orientation has higher orientation precision. Latitude error can reach 0.00021degree, longitude error
can reach 0.00041 degree and altitude error can reach 15 meters. In practice flying, latitude error is 0.0004degree, longitude
error is 0.0008degree, altitude error is 20m.