1.2.2 Notes on using 3D data mode Why 3D? Certain types of noise are prevalent in one dimension and not in others. For example, swell noise may be present in multiple traces within a shot but may not be present in shots before or after. In such cases, a spatial filter in two dimensions results in better noise attenuation. In the shot domain, multiple shot gathers are read before processing starts for the first trace. For each trace, the median filter includes neighboring traces within its gather as wells as corresponding traces from neighboring gathers.