Abstract: A method and a system are disclosed for maintaining accuracy of a photogrammetry system comprising a stereo pair of cameras and characterized by calibration parameters determined at initialization, the system for tracking one of a touch probe and a 3D sensor, the method comprising in use, continuously detecting a presence of a reduced number of 3D target points comprising at least one pair of 3D target points selected in a group comprising at least two 3D target points; measuring image position data associated with the at least one pair of 3D target points of the reduced number of 3D target points; computing at least one updated calibration parameter using the measured image position data and corresponding reference distance data associated with the at least one pair of 3D target points of the reduced number of 3D target points; and updating at least one calibration parameter of the photogrammetry system.

Abstract: In this system, three-dimensional objects (1, 5, 6) in an environment that may be very complex are discerned by identifying their simple contour shapes on images, and the geometric characteristics of these objects and their positions and orientations are then measured. Contours are defined by simple length, inclination, position parameters, etc. The acquired knowledge of the environment is used in each new image to refine the estimates, while introducing new object contours that have appeared, into the model.

Abstract: A tag equipped with markers and, notably, optical markers that also include an electronic label that is adhered and that transmits the relative positions of the tags, or other characteristics of the tags, to a measuring system using telecommunication. Confusion between various tags can thus be avoided, and a greater interaction between the measuring system and the tag can be obtained.

Abstract: In this system, three-dimensional objects (1, 5, 6) in an environment that may be very complex are discerned by identifying their simple contour shapes on images, and the geometric characteristics of these objects and their positions and orientations are then measured. Contours are defined by simple length, inclination, position parameters, etc. The acquired knowledge of the environment is used in each new image to refine the estimates, while introducing new object contours that have appeared, into the model.

Abstract: 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.

Abstract: An attempt is made to localize an object (1) with marks (3) in space, using a video camera (4). A search is made for traces of the marks (3) on the image, to deduce the directions of the marks (3) in the camera (4) view field and the position of the object (1). The algorithm used includes a step in which marks are approximately located by simple formulas, and then a step in which the estimate is improved by an error minimization calculation. Traces are modeled on the image to determine their position with high accuracy, better than the resolution pitch of the camera (4) which therefore does not need to give a very sharp image. The marks (3) are preferably passive marks and may or may not be reflecting, and do not emit any light. The system is not very sensitive to parasite lighting.