Some data from a 3-D marine survey are shown in Figure curtFig1. The top left panel shows part of a shot gather, and the top right panel shows a time slice through several shots from the same source and the same streamer. Marine 3-D data may be broken up into a set of 2-D surveys or treated as a single 3-D survey; more on that later. In this particular case, the data are fairly routine, but they can serve to illustrate the method. The bottom half shows the output of removing half the shots and then interpolating them.