Full-field measurement methods such as integrated digital image correlation bypass the need for post-processing the displacement data upon minimizing the gap between simulation and experiment. This paper discusses the validation of this method by comparing its results with an approach based on compliance values measured from crack mouth opening displacement and load data to calculate mode I stress intensity factors (SIFs) and crack tip positions. Tapered double cantilever beams are used as a test case to evaluate the quasi-brittle fracture response of PMMA. The results demonstrate the ability of the proposed technique to obtain accurate determinations of SIFs and crack length using the tapered geometry. Additionally, both methods yield consistent results, which validates the integrated approach against an independent method.