Devico has now opened two test holes for borehole survey tools at their head office in Norway. The holes consist of a 250m long horizontal borehole for testing of non-magnetic instruments, and a 150m long hole for magnetic instruments.

Since the holes are horizontal and located close to the surface, a reference survey could be performed with a high accuracy GPS. The full borehole lengths were surveyed and the exact positions are known within an error margin of less than 5cm. The borehole trajectories include both straight and curved sections, with a maximum dogleg of 15° deviation over 30m.

Both holes consist of two sets of pipes where a winch pulls a wire through in a loop. Instruments of all lengths and dimensions up to NQ size can be attached to the wire and pulled back and forth throughout the length of the hole. An accurate depth encoder delivered by downhole surveys in Australia has been installed, allowing surveys to be performed at any given depth interval.