The authors describe theoretical and applied research of the magnetic field of the Earth in the Arctic region, carried out by the Geophysical Center RAS and aimed to solve the topical problem of ensuring accurate trajectory of directional oil/gas well drilling and underground positioning using magnetometer techniques. This technology is most efficient as magnetic deviation devices are sufficiently stable and can be used as bottom-hole navigation systems. However, at high latitudes of the Earth, underground positioning based on geomagnetic field in a well drilled at a high slope angle is obstructed due to specific structure of the geomagnetic field and powerful sporadic perturbations related with the solar activity. Geomagnetic perturbations during geomagnetic storms can cause intolerably high error in indications of downhole magnetometers and should be filtered. For monitoring of geomagnetic field alterations, a network of stations and observatories is being rapidly developed, including the highest standard INTERMAGNET. The Geophysical Center RAS takes an active part in arrangement of new observatories in Russia's Arctic. To have correct local magnetic maps, the deviation of the real-Time secular variations in the field intensity from the global statistical model is assessed and the trend of the deviations is followed. Based on the continuous measurements taken in the observatories, the amplitude and frequency of the sporadic perturbations of geomagnetic field due to magnetic storms are evaluated. In particular, the number of days when the amplitude of the perturbations exceeds threshold values set based on the standard accuracy of detection of the magnetic elements in a system of downhole magnetic measurements during drilling reaches a third part of a year and grows considerably in the period when the solar activity is maximum. In such periods, the sustention of the prescribed trajectory needs special correction to remove geomagnetic interference.