In the Alboran Sea, west of the Straits of Gibraltar, the pycnocline depth has been assessed from the signature of a large amplitude internal wave (LAIW) captured by a synthetic aperture radar (SAR) image. First, the coefficients of the extended Korteweg–deVriès model were expressed using two different models of ocean stratification: an interfacial model and a continuously stratified ocean model. Then, via a backscattering model, the same extended Korteweg–deVriès coefficients were computed. This latter calculation was performed along several transects extracted from the LAIW surface signature and through an improved CARMA-derived method. Using the values of the coefficients for the ocean stratification model and those calculated from the SAR image, we obtained solutions for the pycnocline depth and thickness. This method was applied to an LAIW event on 1 October 2008, for which SAR data and stratification measurements by an in-situ experiment were available jointly. The results are that the interfacial stratification model provides only few solutions for the pycnocline depth, while the continuous stratification model allows an interval of solutions for the pycnocline depth and thickness. These models are nevertheless complementary. Extra applications of this method on other ocean regions would be of interest.