GET created new loop of geometry modelling for ATLAS simulation packages. Methodology based on the implementation of CATIA as a hub for geometry descriptions existing in several sources – engineering database (SmarTeam); external CAD systems; XML data using for Muon systems; GeoModel C++ codes using for Calorimeter systems and Geant4 using for simulation. Having CATIA as a hub for all above mentioned sources permits to make different crosschecks of geometry descriptions using in several subsystems of ATLAS simulation. This is important task for the investigation of Data vs Monte-Carlo discrepancies. CATIA will use for generation of new descriptions as well – creation sketches, 3D models, assemblies and their export in XML or C++ code for Geant4 simulation. Methodology was discussed on meetings with ATLAS Simulation head Daniel FROIDEVAUX and CERN Geant-4 group leader John APOSTOLAKIS.Given research is part of the work GET executing according to agreement AA366/10 with ATLAS collaboration.