Snapshot Proper Orthogonal Decomposition (SPOD) and Dynamic Mode Decomposition (DMD) have been used to study the flow features of oblique Shockwave Boundary Layer Interaction (SWBLI). Rainbow Schlieren Deflectometry (RSD) has been used to capture the flow data at 30,000 frames per second. The experimental setup produces a free stream flow of Mach 3.1. A 12° isosceles triangular prism attached to the roof of the test section generates the required oblique shock in the test section. The RSD pictures were used for data analysis to determine the transverse ray deflections at each pixel of the pictures. The analysis focuses on obtaining dominant flow regions in the flow and the corresponding modes at which they occur. This modal information is used to comment on the unsteadiness associated with the flow. © 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.