Predicted Geodetic Reference System for Baghdad City with Aided International Terrestrial Reference Frame (ITRF08)

Historically, the mean Earth ellipsoid is obtained by fitting an ellipsoid of revolution to the geoid. Such an ellipsoid, however, does not necessarily best fit the physical surface of the earth due to the existence of topography outside the geoid. When the distance between geoid and ellipsoid is as low as possible, GPS measurements are accurate because it depends on the measurement on the ellipsoid surface. The ellipsoid is defined as the shape produced by rotating an ellipse about one of its axes, which is a more correct definition mathematically ( Deng, X., 2013). An ellipsoid satisfying the condition that the deviations between the geoid and ellipsoid (in a local sense) are minimized. In this paper, presented a purely geometrically defined earth ellipsoid that best fits the physical surface of the Earth so that the resulting geoid undulation (N) attains minimum in Baghdad city. Using orthometric height (H) and ellipsoid height (h), the size, shape, position of such an Earth ellipsoid have been from observation GPS, methods DGPS with (ITRF).The establishment of a new geodetic reference frame of Baghdad city based on ITRF system which is compatible with space positioning techniques. One of the fundamental objectives of geodesy is to accurately define positions of points on the surface of the Earth. It is important and necessary to establish an accurate geodetic reference frame for measurements and computations of points on the surface of the earth. Recently, this has seen the advancement of technology of using GPS for determination of a three-dimensional geocentric reference system.