Before conducting either a Geological Survey, or a Ground Survey, a grid needs to be created for the area under investigation. Control points are established which allow the site to be synchronized with the National Grid. First of all, a Baseline is established in the prevailing direction of the site. The ends of this are co-ordinated by Triangulation. This fixes the baseline to the surround area, usually by using tape, which is then broken up into suitable units marked by stakes placed in the ground. Once this has been completed points perpendicular to the baseline are set up, again using tapes. In large areas, Pythagorean theory is implemented (A2 + B2 = C2) but when the area being surveyed is smaller, the Pythagorean triangle system is best. All the corners angles of the grid must be at 90° (a square) so the square root of the two sides of the triangle can be calculated, a measurement necessary to determine the hypotenuse of the right angle triangle. The measurements are then used, once the tapes are situated at the two ends of the baseline (often referred to as A and B) so each square can accurately be constructed.

When using magnetometers, it is critical that the operator has no ferrous metal on their person. This includes metal zips, jewellery, shoelace eyelets and even certain metal surgical implants. The reason for this is that the readings are affected by the presence of metals so data can be inaccurate.