Abstract: GNSS height transformation with high-precision is the hot issues in its theory and applications.and it is essential for the practical application of GNSS measurements. This article studies the interpola-tion algorithm by using the first boundary condition, construct the piecewise function of height anomalybased on the basic theory of cubic spline function. The data proved that piecewise function is feasible and effective when it is applied to linear GNSS height fitting.

Key words: piecewise function; GNSS height fitting, height anomaly function, interpolation