1 Transformation from ITRF2000 to WGS84 (Case Study: Iranian Permanent GPS Network, IPGN) By: Azadeh Aghamohammadi a.aghamohammadi@ncc.neda.net.ir Hamid Reza Nankali h-nankali@ncc.neda.net.ir Yahya Djamour y-djamour@ncc.neda.net.ir National Cartographic Center of Iran Meraj Av. Azadi Sq. Tehran Iran Abstract: This document provides a practical solution to the transformation of International Terrestrial Reference Frame (ITRF2000) coordinates of Iranian permanent GPS Network into WGS84 system. WGS84 is geocentric coordinate datum most fit to geoid in Iran (±30m) and is used as a reference ellipsoid. IPGN coordinates are in ITRF2000. ITRF coordinates will in general differ from WGS84coordinates, for two reasons, tectonic motions and reference frame difference. Differences between the ITRF2000 coordinate reference frame and the WGS84 are at the several cm in magnitude. A standard 7-parameter transformation can adequately model these differences at the cm level. Two model have been tested, Bursa- Wolf and Molodensky transformation models. Between these two, Bursa Wolf had the better result and can be used as a better long-term practical solution to these coordinate transformations. Key Words: Transformation, ITRF, WGS84, IPGN, coordinates, GPS network Introduction Iran is situated in a region of collision between two major tectonic plates: Eurasian and Arabian plates with the convergence rate 2.5±2mm (Vernant etal.2004). National Cartographic Center of Iran started to build a GPS permanent network (IPGN) for crustal deformation monitoring and estimating geo hazard in Iran. The data of this network stations are in ITRF and closed to IGS stations, but all GPS stations in local and national networks have coordinates in WGS84. NCC as a center, which is GPS data provider in the country, has to support all users with precise and accurate GPS data. According to the