In this report, we present a photogrammetric system that can be used during welding operation with a robot. It should be able to give the position and the orientation of the Tool Center Point with a high accuracy (less than 0.5 mm). After a view on the historic of PosEye®, we describe its two different ways of working: using active or passive markers. We then explain one way to improve the accuracy of the sensor by taking in account the distortion of the image due to the projection. This part is followed by investigations on a so-called “flash collar” which permits to fix diodes when we use passive markers. We finish by some tests to have a better idea of the accuracy of the sensor. This accuracy is only available for the position, as it has been realized on a Coordinate Measuring Machine which is only able to give information on its position.