The invention relates to a device (1) projecting a reference line, having an electro-optical distance measurement unit that guides an optical reference beam (RS) along a defined reference path (RP), wherein at least one part of the reference path (RP) may be detected upon passing through by the human eye and/or detectors as a reference line. In conjunction with passing through the reference path (RP), a distance measurement occurs to at least one point (Pi) on the reference path (RP), particularly to a plurality of points (Pi), by transmitting a measurement beam that is parallel or coaxial to the reference beam (RS) or using the reference beam (RS) as a measurement beam. After receipt of portions of the reflected measurement beam, a signal is derived from said portions and a distance (Di) from at least one point (Pi) is determined from the signal, wherein the guidance along the reference path (RP) is repeated at least once more and, upon each instance of passing through the reference path (RP), a distance (Di) or distance-related variable is determined for each point (Pi).