Abstract: A stretch corrected wireline depth measuring system is set forth including method and apparatus. It forms a log quality indication which indicates those occasions where the tool velocity is outside acceptable limits. The apparatus utilizes calibrated encoder wheels, preferably a redundant and duplicate pair, to form pulse trains indicative of surface wireline velocity. Additional measurements are made of wireline tension, and magnetic marks on the wireline are observed. All of this data is input to a CPU which determines the raw depth, and adjusts this value with depth corrections. The device calculates wireline stretch as a function of tension and total wireline in the borehole. This enables formation of output data as a function of depth including cable tension, tool speed, depth correction and log quality in the event that tool velocity is outside an acceptable range.