Results of an experimental research by the shadow method and background oriented schlieren (BOS) method of the flow field in shock tube channel after initiation of the sliding surface discharge and the volume discharge of nanosecond duration are presented. Simultaneous registration of the flow field by two methods gives the capability of complete qualitative and quantitative description of the shock-wave processes arising from the interaction between the pulse discharge and a highspeed flow in the channel of the shock tube. Vector field of displacement between two images is evaluated using cross-correlation technique. The density is obtained by solving Poisson equation with special boundary conditions. It is shown that BOS method provides quantitatively reliable data for the structure of flow field corresponding to a classical shadow method. It provides good quantitative results for the shock waves propagating in the area of initiation of discharges.