The Arsac array has four probes but is placed linearly along locations 0 (zero), 1, 4 and 6 units of distance. There are a total of 6 combinations by pairing any 2 probes among the 4, but in the Arsac array, the separations of the pairing form a continuous sequence of distances of one unit to 6, with no gaps or redundancies. This means that with one setup of the 4 probes in the Arsac manner, the effective resistivities of 6 distances may be measured on the soil surface; this is in contrast with the resistivity of just one distance per setup using the standard 4-probe measuring methods of Wenner and Schlumberger. The Arsac 4-probe method may therefore be highly economical in terms of time saved.