Measurement results of femtosecond laser pulses with the home-made collinear and non-collinear, large dynamic range, scanning third-order correlation technique are analyzed theoretically and experimentally. It is found that the dynamic range is low for the collinear scanning third-order correlation method because of the direct third harmonic generation of the fundamental light in air. While the non-collinear measurement does not have this problem and thus has a higher dynamic range, the non-collinear angle and spot size have a significant influence on the measured pulse duration. In particular, both theoretical simulation and experimental results show that the measured pulse duration increases with the beam angle and spot size in this latter case. Although both noncollinearand collinear approaches can help locate the weak satellite pulses, due to the artificial pulse broadening introduced in the non-collinear scheme, it will be difficult for using this method to resolve or distinguish the detailed structures around the main pulse or any closely located neighboring pulses.