Incorporating in the geometric calibration images in which the calibration chart is only partially visible can help to make calibration process much more efficient and more accurate. This is particularly true in the case of systems involving a larger number of cameras. A calibration tool developed by us that makes it possible to utilize also images in which only a part of the chart can be detected is described and the benefits of using such a tool compared to the traditional checkerboard chart calibration are demonstrated. Examples illustrating the implications of the requirement that all chart points must be detected in the image on the spatial distribution of the corner points used for calibration are shown and the impact of the resulting distribution on the accuracy of the calibration is analyzed, using both synthetic and real data sets.