In the presence of a gradient of sound propagation velocity in the location medium, the trajectory of sound rays deviates from straight lines perpendicular to the surface of the sound wave front. Refractive deflection of the rays occurs in the direction of the region of the medium with a lower sound propagation velocity. Obviously, the curvature of sound rays leads to a shift of the sonicolocation irradiation spot on the reflecting surface of the location object. This displacement determines the error of the sonicolocation measurement, and in some cases can lead to the formation of an acoustic shadow zone in which sonicolocation measurements are practically impossible.

The sonicolocation method of surveying control and surveying of mine workings is used in the practice of mining enterprises relatively recently. Currently, this method of distance measurement is used in the surveying of dredge ranges, deep open-pit ore dumps, inaccessible underground salt leaching chambers and underground storage of petroleum products, as well as mine shafts and boreholes, conducted by drilling.

When applying sounding equipment in surveying work naturally arises the question of its accuracy and, therefore, the possibility of using it to solve specific engineering problems. At the present time - in the period of development and formation of sounding method of measurements in surveying - this issue is of particular relevance.

Underground polygonometer courses are laid in order to create a system of points with known coordinates in mine workings and to solve mining engineering tasks. Since such runs are the basis for solving most of the surveying tasks, their quality and timeliness depends on the success of the surveying service of mining operations as a whole.

When designing, producing and evaluating surveying works, the question constantly arises as to what is the criterion of their necessary and sufficient accuracy. The rich practice of underground mining allows to assert that such criterion is technically correct and economically feasible solution of production tasks related to the field operation. Surveying works carried out at a mining enterprise are designed to provide it with the necessary mining engineering, mining geometry and geodetic data. Naturally, the volume and accuracy of these data should be determined by the production requirements, which are expressed in the values of production tolerances. Conducting surveying work without full consideration of the established tolerances can lead to a number of complications of the process of mining of minerals - to disrupt the normal operation of the enterprise. It should be said that overestimated accuracy of surveying works is as harmful for production as insufficient; both the first and the second lead to significant losses of time and money, to violation of normal surveying service of mining operations.