The acquisition and assessment of geotechnical data are integrated parts of subsurface and surface
construction works. Decisions about feasibility, design, and construction depend on predictions based
on the acquired data. Thus the quality of these data substantially influence construction work.

For an economical and safe construction of a tunnel a continuous adaptation of the excavation method is
required, which includes the quality and quantity of the used support according to the actual ground conditions.
The adaptations base on a continuous observation of the rock mass during excavation.

One essential part is the acquisition of geotechnical parameters of the rock mass, such as geometrical
properties of discontinuities and their spatial orientation.
Present practice is to acquire these data by manually sketching the rock mass and measuring certain
discontinuity orientations using a compass-clinometre device which requires manual access to the rock structures.
The resulting data have several drawbacks, they

• are incomplete
• have no metrics
• are inconsistent
• are not post-processible