The programme plots the time of flight versus the measurement depth. This plot is called a dromochronic. It usually appears as a couple of straight lines making an angle. The slope of the superior part (shallow depths) corresponds to the probe when located in front of the foundation, and that of the inferior part corresponds to the probe when located below the bottom of the foundation. The change of the slope takes place at the position if the bottom of the foundation, which can therefore be determined after a slight correction.

The top of the tube is the reference for zero depth. The length of the foundation is given between this tube top and the bottom of the foundation.

Two seismic velocity are calculated by the software : the seismic velocity in the foundation and the seismic speed in the ground under the foundation). They are meant to verify that the two slopes determined from the graph do represent the part in front of the foundation and that below its bottom.