WASET
    Hyun-Gwang Cho and  Wan-Seok Yang and  Su-Jin Kim and  Jeong-Seok Oh and  Chun-Hong Park,  Error Factors in Vertical Positioning System.   journal   = {International Journal of Mechanical and Mechatronics Engineering}, [online]. World Academy of Science, Engineering and Technology.
    November 2011, vol. 59(11). 2223 - 2228
    [viewed 24 April 2024]. Available from: https://publications.waset.org/pdf/15233.