A method of calibrating a camera (4, 22) disposed on a mobile support (21). The camera takes an image of a test object formed of at least three marks appearing in the field of the camera, and analysis of the image gives the initial position and orientation of the camera with respect to that of the test object, which are known in an application. The support (21) can then be moved towards an object (28) of which the camera takes images. As the movements of the support are measured accurately, analysis of the images of the object gives the precise position and orientation of the object with respect to the camera and with respect to the test object. One application is the recording of road signs (28) in order to compose databases for network management or for an on-board navigation system.