Experiments have been conducted to study the impingement fiowfield, over a double wedge deflector, produced by the impingement of an overexpanded supersonic jet. The jet has an exit Mach number of 3.1 and an expansion ratio of 0.81. The distance between the nozzle exit and deflector apex was varied from 2 to 5 times the nozzle exit diameter. The experiment consisted of schlieren flow visualisations and measurements of pressure distribution. Load coefficient has been obtained by integrating the measured pressure distributions. Boundary layer thickness and skin friction coefficient on the deflector surface have been calculated by solving compressible turbulent boundary layer equations, using moment integral and moment-of-momentum integral equations in conjunction with the measured surface pressure distributions.