For a given source, we have a limited range of receivers (perhaps 3-5 kilometers), and vice versa. Receiver positions are often sampled two or four times as densely as source positions. In marine data, both are evenly sampled relatively, but a spatial Fourier transform must pay attention to aliasing or edge effects from the short span. Land data will be much more arbitrarily sampled.

Define the coordinates of offset
and midpoint . Resorted data can be written as
*d*(*s*=*y*-*h*/2, *r*=*y*+*h*/2, *t*). The well-sampled midpoint coordinate covers
the entire span of the survey.

11/12/1997