What is dipole-dipole array?

Layout the electrode as figure below and get the first point. The point lacates on the midperpendicular of BM.

Then keep the location of AB, move MN rightwards by one electrode spacing and get the next point. Do it again and again, you can get a rolling line.

After complete the last point of this rolling line, move A,B,M,N rightwards at the same time, by one electrode spacing, and do the measurement just like the first rolling line.

At last, you can get a section like the figure below: