Accuracy Analysis of GNSS (GPS, GLONASS and BEIDOU) Obsevation For Positioning Khomsin, Ira Mutiara Anjasmara, Danar Guruh Pratomo and Wahyu Ristanto E3S Web Conf., 94 (2019) 01019 Published online: 08 May 2019 DOI: 10.1051/e3sconf/20199401019