“…Depending upon the required accuracy, the three-axis systems, based on laser gyros, fiber optical gyros or the specialized analytical gyro verticals with the reduced number of sensitive elements [18] can be used as SINS. The algorithms of measuring the basic geometry parameters of railway track, such as longitudinal level, cross level, curvature, inclination etc., were discussed in [19,20]; they can be realized in automatic apparatus [15,16]. The latter is not valid for procedures, providing identification of the rail rolling surface flaws.…”