<title>Obstacle detection algorithms for rotorcraft navigation</title>

Wires can be hardly visible and thus present a serious hazard to rotorcrafts flying at low altitudes. Vision systems capable of detecting wires in time to avoid collisions must be able to find in the input images curves less than one or two pixels wide. This paper describes a study on the performance of wire detection using a sub-pixel edge detector algorithm proposed by Steger. This algorithm was tested on a set of images synthetically generated by combining real outdoor images with computer generated wire graphics. Its performance was evaluated both, at the pixel and the wire levels. It was observed that the algorithm performs well, provided that the wires are not too thin (or distant) and that some post processing is performed to remove false alarms due to clutter.