The topographic survey of the cave has been performed using Suunto and Soviet "geological" compasses and clinometers. In addition, two Casio watch altimeters were used to control the depth by repeated incremental measurements. The depth of the lowest point in the cave was 1720m according to altimeters, but 1710m according to the clinometer measurements; the later figure has been eventually taken as an "official" one. In general, the resultant map and profile (Figure 4) correspond to the BCRA Grade 4.
In September 2000 the MRDE team made independent depth measurements up to -1410m point with two precise altimeters and found a coincidence within 5 meters with the depths estimates for various points previously made on the basis of clinometer survey.