Time measurement with photocells is a frequently used method in quantifying performance. Although this method has a high accuracy, it also has some limitations when performing a detailed temporal analysis of repetitive multiple movement cycles in a complex technical sport, such as alpine skiing. Therefore, the aim of the present study was to develop a new method for time computation from surveyed trajectories using a real time kinematics global navigation satellite system (GNSS RTK) and to compare this with traditional photocell measurements. Two validation experiments were performed with 1) a trolley and 2) running over a 10-m distance. An application experiment was performed on eight alpine skiers on a slalom run, in which the GNSS RTK system was compared to photocell time recordings. The validation experiment demonstrated small mean time differences (<.0015 s) with no systematic bias, with a scatter of time differences that were velocity dependent and were diminishing at higher velocities. In the ski experiment, the multiple gate to gate and lag times demonstrated that the GNSS enabled a detailed performance analysis. The measurements using GNSS RTK showed a high validity and potential as a tool for more specific analysis of performance in alpine skiing.