An experimental method is proposed to determine and remove the geometric component in charge pumping (CP) measurements. This method uses CP-current data of different gate length transistors (LG) with fixed gate width (WG) to obtain an empirical model for the remaining carriers in MOSFET channel after the switch off. This allows to investigate the geometric component (GC) as a function of device gate length. Using this approach, we have been able to extract CP-current without GC. To validate this procedure, we have explored the parasitic effect of GC in negative bias temperature instability (NBTI) and radiation degradations. We present, in this paper, the experimental evidence that GC increases after irradiation and during the NBTI stress, which is most likely caused by Coulomb scattering of created traps. This implies that the precision of radiation- and NBTI-induced trap estimation is affected as well as their creation dynamic. We also give the experimental results after removing the GC. They show a same power-law time exponent n for all transistors. This procedure is valuable to correct CP-based method data for degraded devices.