A method for controlling an unmanned aerial vehicle using an electronic device obtains movement data of the electronic device detected by an accelerometer of the electronic device, and converts the movement data of the electronic device to control signals. The biasing circuit has a first transistor and a second transistor. The first database contains a plurality of skills and an allocation of minimum prerequisites for capabilities required for the respective skills. An elongate reamer has a longitudinal axis, a first end and a second, opposing end. Each first conductive pad is in electrical contact with a respective one of the second contact regions. In one embodiment, a reference image is compared with each image in an image stream, and a similarity value is calculated to reflect the degree of similarity between them.