Calibration of object position-measuring apparatus

A method for converting coordinates of measurements obtained by an apparatus for determining the position of a remote object is disclosed. The method comprises obtaining a first position measurement of a first object located at a first position. The first position measurement is made by the apparatus and is expressed in a first coordinate system that is dependent on the position and/or orientation of the apparatus. The method further comprises obtaining a second position measurement of the first object at the first position. The second position measurement is made by a position-measuring device co-located with the first object and is expressed in a second coordinate system that is independent of the apparatus. The steps of obtaining first and second position measurements are repeated one or more times based on objects located at different positions. A determination is made of a transformation for transforming coordinates between the first and second coordinate systems based on the first and second position measurements.