A surface processor uses an environmental profile to determine the sub-surface length of tubing disposed in a well bore. Information relating to tubing properties is stored in a memory module of the surface processor. The environmental profile includes data relating to well bore ambient conditions and the operating parameters of well equipment. Surface processor calculates the tubing elongation or length reduction corresponding to the environmental profile. Surface processor may repeat this process to develop a measured depth chart for a well. Logging operations performed in conjunction with the sub-surface length calculations allows formation data to be associated with the measured depth chart.