Patent ID: 7612872

Claim:
A method for measuring flatness of a foundation to which a structure, machinery or equipment is to be mounted, comprising the steps of: defining an x-, y-coordinate system; determining x- and y-coordinates within the coordinate system of positions at which mounting points are to be located and storing the coordinates in a reference table in a computer; generating and moving a laser beam in a horizontal plane in a manner which causes the laser beam to sequentially intercept each of the measurement points; generating signals from a respective position sensor located at each measurement point based on illumination of the sensor by the laser beam; determining coordinates of each of the measurement points from the signals generated by the respective position sensor and comparing the determined coordinates to the stored coordinates of the measurement points so as to match a height measurement obtained from a vertical position of impingement of the laser beam on the sensor at each measurement point with a particular measurement point; and determining the actual height of each of the measurement points from height measurements obtained as an indication of the flatness of the foundation; wherein the coordinates determining step comprises using a time difference between when a single laser beam first enters and then leaves a detecting area of the respective position sensor at each of the measurement points in a calculation to determine the distance of each measuring point from the laser based upon the length of the detecting area in said horizontal plane.