Geodetic support for construction and operation of high-speed railway lines is associated with the need for high-precision geodetic work at all the stages of the life cycle of such structures. Arrangement of a setting-out network requires special responsibility, calculating the accuracy of determining its points' heights is the subject of the article. The insufficiency and imperfection of the results of previously performed research on the topic is shown. It is proposed to carry out computations based on the design parameters of high-speed railway lines. The required density of benchmarks for establishing a set-out network was calculated. The demands set forth in the regulatory documents of various countries operating high-speed railway lines are outlined. The validity of the obtained result and the feasibility of achieving it with existing geodetic measurement methods are demonstrated. Potential directions for future research regarding geodetic support for high-speed railway construction are identified