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With the development of modern space technology, accurate point coordinates have been widely used since the official opening of CGCS2000 in China. High-resolution weather radar, with a range bin size of usually less than 100 meters, needs more precise coordinates to represent meteorological echo positions in today’s operational applications. For the availability of radar echo’s accurate coordinates in CGCS2000, a series of mathematical relationships have been established between the Earth ellipsoid and radar RPS (a reference positioning sphere of radar) and have been utilised to compute typical coordinates associated with radar echoes, such as geodetic coordinates, geocentric coordinates, radar reference coordinates and radar observation coordinates. The error analysis of the earth spherical approximation method shows that horizontal deviation is the main error expression and correlates with radar geographic position and echo’s radar observation coordinates. The deviation level of high-or-low-latitude radar is greater than that of middle-latitude radar. The maximum deviation increases with the radar detection range. The ratio of the maximum deviation to detection range from 50 km to 400 km is between 2‰ and 5‰. The error influences can be ignored in general but not in some high-precision computations.