of guiding the railroad track positioning device of a track renewal and maintenance machine as the machine moves in the track working direction to this end the curvature of a track section to be worked upon comprised in a chord of predetermined length is measured and as a function of this curvature the direction of a second chord is measured one end of this second chord being coincident with the rear end of the section whereas its predetermined and constant length is so selected that its other end lies on the already renewed or maintained track section and shows the position of a point of this section before the renewal or maintenance works application_number US 47124383 A description in fig1 afbc denotes a circular arc showing the center line of the track or a rail or an equivalent arc lying at a constant and predetermined distance from the track a and b are two points of this arc lying on or corresponding to the old track section point p is the point where the track is treated and where the track undergoes a geometric deformation the arc pc is shown on purpose with an exaggerated deformation and illustrates the actual track position after the treatment maintenance or relaying while arc pc in dash lines is the.