Abstract: The article made the theoretical and empirical analysis and research on the applicability ofhigh-precision GNSS measurement projection deformation method in the construction of coordinate systemsfor water conservancy projects in high-altitude areas. It combines the example of the topographic mappingproject of the water conservancy interconnection project in high-altitude areas of Yunnan Province to analyze the causes and derive formulas for the influencing factors of projection deformation in engineeringmeasurement. The different combinations of projection surface and projection central meridian in projec.tion deformation calculation methods are analyzed and compared. Empirical calculation research showsthat in high-altitude areas, the project takes the average elevation of the measurement area as the projec.tion surface and calculates the central meridian in reverse. It sets up a projection with a central meridianminimizes projection deformation, and establishes the best coordinate system elfect.

Key words: high altitude areas, length distortion, projection, plane projection zone