For heterogeneous wireless network, the use of positioning information with global navigation satellite system (GNSS) such as global positioning system (GPS), quasi zenith satellites system (QZSS) in Japan and the global navigation satellite system in Russia (GLONASS) has been very effective. In this paper, the quantitative relation of positioning accuracy on various GNSS and sky view factor are described. We propose the application of a concept of the sky view factor for position accuracy on GNSS, and achieve quantification of sky view factor by image processing. The relationship of positioning accuracy on GNSS and sky view factor are evaluated. At the point where sky view factor is 88.2%, the positioning accuracy is estimated lower than 1m using the multi GNSS receiver such as GPS+GLONASS or DGPS+GLONASS. At the point where sky view factor is 42.2%, the positioning accuracy is maintained lower than 1m. At the point where sky view factor is 11.1%, positioning accuracy is improved lower than 3m using DGPS+GLONASS receiver. Furthermore, as an advantage of QZSS compared to GPS at 11.1% point, the impossible positioning time in 30minutes is improved from 80seconds on GPS to 4seconds on QZSS. Presumption of the positioning accuracy by sky view factor is achieved. We conclude that sky view factor is very effective in presumption of positioning accuracy at mobile location.