2006_04 Coordinate Reference Systems.ppt

School of Geodesy and Geomatics,WHU 4 Coordinate Reference Systems What is Reference Systems ? Why we need Reference Systems ? What is a Spatial Reference System? 2D Reference System 4 Coordinate Reference Systems 3D Reference System 4 Coordinate Reference Systems Refercnce coordinate systems in satellite geodesy are global and geocentric, because the satellite motion refers in the center of mass of the earth. Terrestrial measurements are local in character and are usually described in local reference coordinate systems. The relationship between both systems must be known with sufficient accuracy. Since the relative position and orientation changes with time, thc recording and modelling of the observation time also plays an important role. 4 Coordinate Reference Systems Note:The results of different observation methods in satellite geodesy refer to particular reference coordinate systems which are related to the individual methods. These particular systems are not necessarily identical because they may be based on different data and different definitions. Often the relationship between these particular systems is known with an accuracy lower than the accuracy of the individual observation techniques. Establish precise transformation formulas between systems is one of the most important tasks in satellite geodesy. 4 Coordinate Reference Systems reference system and reference frame reference system is understood as the conceptual idea of a reference system including the fundamental theory and standards reference frame means its practical realization through observations and a set of station coordinates. 4.1 Cartesian Coordinate Systems and Coordinate Transformations In a Cartesian coordinate system with the axes x, y, z，the position of a point P is determined by its position vector xp, yp, zp are real numbers 1.Rotation around the z-axis by the angle γ with identical origin ： can be realized through the matrix operation 2.Rotation around