For precision levelling works are now more often used digital levels and code-scale staffs. Advantages in (and problems with) their application to the regular line-levelling are well known and described. However, when using the digital levelling for measurements in specific local geodetic networks, monitoring networks and inside of buildings and underground spaces, new problems appear with the signalisation of the observed points, readability of the code (non-uniform illumination), temperature changes etc. The article informs about the application of two types of digital levels (Sokkia SDL-2, Trimble Zeiss DiNi 12T) in the experimental subterranean levelling network for the basement settlement monitoring of a ten-floor building; the solution of marking of the points, field calibration and the system calibration of digital levels.