47 Heßler, Christoph Robert Ohlig, Markus Reimann, Stephan Schuett, Petra OPE Proc. 14th International Particle Accelerator Conference 14th International Particle Accelerator Conference JACoW Publishing Geneva Venice, Italy 978-3-95450-231-8 10.18429/JACoW-IPAC2023-THPA123 English 4251-4254 The high-energy beam transfer lines at GSI serve numerous experimental stations such as HADES, HTC and HTD as well as the fragment separator FRS and the storage rings ESR and CRYRING with a wide range of different heavy ion beams from the SIS18 synchrotron. The large amount of experiments carried out during beam times under different beam conditions require frequent changes of beam optics and beam steering in the transfer lines. In the past, the online model tool 'Mirko Expert' was available for this purpose, which however is not compatible with the new control system infrastructure. Therefore, a new online model application based on the MAD-X beam dynamics simulation code and the JMad programming interface is under development in Java. This paper presents the concept and features of the new online model application, as well as possible future extensions. Efforts to overcome discrepancies in the present Mirko and MAD-X optics models are also discussed. Published by JACoW Publishing under the terms of the Creative Commons Attribution 4.0 license. Any further distribution of this work must maintain attribution to the author(s), the published article's title, publisher, and DOI. ; Proc. 14th International Particle Accelerator Conference ; 33, ; PUB:(DE-HGF)8, ; PUB:(DE-HGF)7, ; Accelerator Physics mc6-beam-instrumentation-controls-feedback-and-operational-aspects - MC6: Beam Instrumentation, Controls, Feedback and Operational Aspects mc6-t33-online-modelling-and-software-tools - MC6.T33: Online Modelling and Software Tools Contribution to a conference proceedings 2023 2023-05-07 - 2023-05-12 GSI-2024-00179 2023-05-07 - 2023-05-12 2023 https://repository.gsi.de/record/348133 https://doi.org/10.18429/JACOW-IPAC2023-THPA123