The Foerster Ferex 4.032 DLG used by Geophiz.biz is a multi sensor fluxgate gradiometer, with 4 sensors spaced 50cm apart. It is guided by a kinematic GPS system, and so it is unnecessary to set out a grid when using this system. Because of the sensor spacing, higher resolution data is collected, which has benefits both in the clarity of the imagery and in the ability to interpret the anomalies discovered. An added advantage is that topographic data is collected at the same time as the geophysical survey (click the link below to go directly to the Foerster website for more information).