We present a vision-based landing algorithm for an autonomous helicopter under complex environment (there are several
suspected targets). The algorithm is integrated with algorithms for visual acquisition, recognition of the target and
computing the navigation information. In our algorithm, we use international standard landing mark as our landing target.
The experiment results demonstrate that our algorithm has the feature of robustness, accuracy and real time. It can meet
the actual flight requirements well: the average processing time of a 640×480 image is less than 40ms; the position error
is below 5cm in each axis of translation; the angle error is below 3.5°. Based on the algorithm, we win the champion of
the aerial robot competition in the 2008 China robot competition and the RoboCup China open.