Widely used in mechanics is the method of surface parameters investigation by indentation of some kind of penetrator into test surfaces and registration of the indentation/load dependence through the whole test duration. A small ball made of hardened steel or diamond pyramid, so-called Berkovich pyramid, is used for penetration. An actuator performing the indentation process is used for displacement enforcement as well as for load measurement. Mainly two types of devices are in use: based on piezoelectric effect or purely electromagnetic LVDT. Knowledge about the penetrator tip is essential for the proper evaluation of the measured parameters and knowledge about the actuation method is also desired for better identification of the whole system parameters when using DSP type algorithms at the stage of experimental data elaboration. In this paper we deal with some kind of DSP elaboration of the experimental data. Our attitude is based on successive digital filtration applied to the experimental data as well as to the intermediate stages of calculation, especially for compliance estimation. Different digital filters have been developed and applied to the experimental data. Some conclusions have been taken out due to the precision of the layer thickness estimation based on data obtained by indentation of the investigated surface with a Berkovich pyramid driven by a piezoelectric actuator. The Boussinesq/Sneddon theory has been used as the basis of our analysis. Titanium azide layers imposed on a magnesium alloy have been tested using PVD method. Obtained results especially due to the hardness/indentation plot allow evaluating the layer thickness, which should be also compared with thickness values evaluated by other methods.