The utility model discloses a transmission line range unit of low cost fast and location method, take the photograph camera, image processing circuit and central processing unit including the first camera of taking the photograph, second, the image processing circuit who states adopts the threshold processing circuit that floats, unsteady threshold processing circuit including reverse protective circuit, low pass filter circuit, signal amplification circuit, peak hold circuit, voltage follower, voltage comparater and amplitude adjustable threshold voltage generater. The utility model disclosesby the minimum system composition of one or a plurality of miniature camera head and singlechip, the camera absorbs the consecutive image of space power transmission line from the circuit side, 25 frames of per second, and the singlechip is gathered, is handled every frame image signal, and can be low -cost and the giving security for unmanned aerial vehicle finds range of quick accuracy.