It is provided a method for determining when to trigger positioning of a portable key device used in access control for an electronic lock controlling access to a restricted physical space. The method is performed in a positioning determiner and comprises the steps of: obtaining movement data from a motion sensor of the portable key device, the movement data indicating movement of the portable key device; determining when the movement data indicates a stop in motion of the key device; and triggering positioning of the portable key device when a stop in motion of the key device has been determined.