GNSS navigation has become a part of the drilling and leading manufactures have this operator aid as an optional feature for their products. Its advantages in quarries and open pi mines have not known and understood widely so far. The objective was to find out if navigation systems improve borehole and drill pattern quality and whether it affects to production rates in mines and quarries. The measurements were committed in Talvivaara open pit mine in Finland. The drilling results of two similar drilling rigs, drilling similar holes, were investigated. The results showed that the drilling accuracy for the start points, compared to drilling plan, is more precise when GNSS navigation is used. To achieve the desired drilling depth is app. 2 times more accurate when the GNSS navigation is used. The drilling depth seems to be too short with a navigation system and it is caused partly or mainly from the hole curvature. The average shortage is only 27 centimetres whereas the holes drilled without the navigation are in average 32 centimetres too deep. The standard deviation of the depth of the holes causes more floorhumps when drilling without a navigation system and that increases the need to smooth the floor with blasted rock. At the target level the overall accuracy is also better for drilled squares when drilling with a navigation system. This too affects to floorhumps and decreases the needs of the filling as well. The marking of the boreholes and surface levelling is done before the drilling and using GNSS navigation assisted drilling this work phase is unnecessary. This saved time can be used to drilling operations and increases the production rates. The overall increase in production is found to be 12.9 % in Talvivaara scale of operation when typical parameters of DP1500i drilling rig are used. This means app. 3.1 million tons more ore per a year. Further use of true coordinates of the boreholes was limited for training purposes at the moment and satellite black-outs hadn’t been experienced in 24/7 operation so far.