In diagnostics of existing road pavement structures, deflection measurements have fundamental meaning because of the ability to assess present stiffness (bearing capacity) of whole layered construction. During test loading, the reaction of pavement structure to applied load is measured in a central point or in a few points located along a straight line at a 1.5-1.8 m distance (i.e. Falling Weight Deflectometer) or in similar spacing equal to 20-30 cm.
Typical measuring techniques are productive and precise enough for the most common pavement structures such as flexible, semi-rigid, and rigid. It should be noted that in experimental research as well as in pavements in complex stress states, measurement techniques allowing observation of pavement deformation in 3D would have been very helpful. A great example of that type of pavement is a block element pavement structure consisting of paving blocks or stone slabs. Due to high stiffness and confined ability of cooperation of surrounding block elements in that type of pavement, fatigue life is strongly connected with displacement distribution. Unfortunately, typical deflection measurement methods forego displacement observations and rotation of single block elements like paving blocks or slabs. Another difficult problem is to carry out unmistakable analysis of cooperation between neighbouring elements.