Abstract: Up to now,various scales of national fundamental spatial data are available with ease,so it is very urgent to integrate so much data in a unified geographic coordinate system for social services.However,the traditional GIS functions are specially developed for local plane coordinates system,such as the calculation of distance and area.In fact,because of the quite different principles between the plane system and curve system,it is impossible to simply use the traditional methods for geometric measurements.In this paper,for the representation of geographic data in the referential ellipse's earth core geodetic datum,the calculations of two basic geometric measurements of distance and area are analyzed through experiments.First,the limitation of using plane surface instead of curve surface is analyzed concerning with different covering ranges and scales,then the geometric measurements on the curve surface are tested.