Toward a successful 3D and textural reconstruction of urban scenes, the use of both single-row based telemetric and photographic data in a same framework has proved to be a powerful technique. A necessary condition to obtain good results is to accurately calibrate the telemetric and photographic sensors together. We present a study of this calibration process and propose an improved extrinsic calibration technique. It is based on an existing technique which consists in scanning a planar pattern in several poses, giving a set of relative position and orientation constraints. The innovation is the use of a more appropriate laser beam distance between telemetric points and the planar target. Moreover, we use robust methods to manage outliers at several steps of the algorithm. Improved results on both theoretical and experimental data are given.