This study presents the validation of a regional ionosphere model (TUWR) developed using multi-GNSS observation data, specifically GPS and Galileo. The model was assessed against well-established ionospheric models, including those from CODE and IGS, through ionospheric map evaluations, and station-specific performance analyses. The results indicate that the TUWR model provides highly comparable VTEC estimates, with average deviations of less than 1 TECU from reference models. The findings confirm that the integration of multi-GNSS data significantly enhances ionospheric modeling accuracy. Additionally, the TUWR model demonstrates its applicability for single-frequency GNSS users, offering a reliable approach for mitigating ionospheric effects in positioning applications. The results highlight the importance of leveraging multi-GNSS solutions to improve ionospheric corrections, ultimately contributing to more precise and robust satellite-based navigation.