Geometric properties are used to reliably identify gestures of a bare or gloved hand. A set of optimum hand gestured were experimentally identified. The hand gestures are used to issue commands to a wheelchair. The effect of skin color is eliminated by using a back-lit surface. The system is scale, position and orientation invariant. Yet position and orientation of two hand gestures are used to issue motion control commands in two modes; manual and auto. In manual mode the position and orientation of a selected hand gesture are used for speed and steering control. The interface works well with either of the hands and can be interchanged anytime without any changes to the system. The hand gestures are organized in a hierarchy taking into account the ergonomics, reliability and the mode of operation. The manual and auto mode operations are demonstrated by presenting the results showing each mode of operation.