D. N. Suzanskiy - Ph.D. (Eng.), Associate Professor, JSC «Concern «Vega»
V. Yu. Popov - Dr.Sc. (Phys.-Math.), Professor, Lomonosov Moscow State University, Financial Academy with RF Govemment
O. A. Ivanova - Ph.D. (Phys.-Math.), Engineer, JSC «Concern «Vega»

One of the possible ways of building an unmanned air vehicle (UAV) reference trajectory in the Nap of the Earth flight is considered in the work. The trajectory is based on a digital contour map for the vertical-plane terrain following. The possibility of obstacle approximating (in the vertical plane) with conics (semicircles and semiellipses) is the basis of the method. The hydrodynamic theory of incompressible ideal fluid-s plane irrotational motion, the complex variable theory and the conformal mapping method are also used for building the UAV reference trajectories. Two variants of description of a ground profile are suggested. The streamline functions for the irrotational flow of an ideal fluid past such obstacles are obtained. The differential systems describing the family of streamlines which can be used as reference trajectories are also obtained. Some results of the suggested approach modeling are also given.