Recently, GPS has become the most significant used survey instrument. The GPS performance is affected by the number of tracked satellites, so its performance is degraded in limited sky regions. Thus, one of the good solutions is adding other GNSS satellites and make combined solutions between GNSS systems to increase the number of satellites. In this study, there are two networks; the permanent and regional networks. In the permanent network, a comparative study using GPS, GLONASS and combined GPS with GLONASS has been implemented to investigate the advantages and disadvantages of combined solution. Data processing has been performed with different values of elevation cut-off angles. The regional network has been processed using different cases of combined satellite systems. These systems are GPS, GLONASS and BEIDOU. For the permanent network, in the condition of open sky view, the average coordinate errors for GPS, GLONASS and combined solution are respectively 16.5, 25.0 and 36.0 mm. The solutions by using GPS only are more accurate than other cases and there are no clear improvements from combined GLONASS with GPS observations. The significance of combined GPS and GLONASS solutions arise when the elevation cut-off angle was set to 40° and more which represent the extremely limited sky view such as urban and narrow canyons. For the regional network, the results indicated that combined GPS with BEIDOU is the best case because it achieved the smallest closure error with 19.50 mm. GPS only is better than GLONASS only, BEIDOU only, combined solution between GPS and GLONASS and combined GPS with GLONASS and BEIDOU.