Resection can be used to measure the velocity of a glacier even where the co-ordinates of rock stations are unknown. The method is an adaptation of conventional semi-graphic resection and requires that the rock stations (targets) can be identified on a map. It can be extended to cover further points resected with the same targets even if there is no map. Stations whose velocities have been determined can then be used as control for detailed studies, thus avoiding the necessity to visit rock stations which, in rugged country, may be inaccessible.