An X-ray collimator has a collimation plate, and a shielding box made of a tungsten plastic composite, the shielding box having an opening on the top and the bottom thereof respectively, and a support part for supporting the shielding box. The guillotine preferably includes an angled blade in cross section such that when the needle is cut it is projected further through the diaphragm and into the device. This string of data is used to determine the velocity of travel for use in navigation operations.