This article illustrates a method to measure, visualize, and statistically test tamping effectiveness on track geometry using and comparing two different measurement systems: an onboard system mounted on a regular passenger train and a specialized measurement train system. The proposed analysis method can be generalized to assess the impact of other track maintenance activities. Track quality variables, such as the longitudinal level, were measured to assess tamping effects on a 1250 m section of the Swedish Iron Ore Line in autumn 2022. The onboard system provided frequent measurements before and after tamping, capturing immediate to 3-month effects, while the regular system enabled a 21-month follow-up. The analysis segmented the tamped and comparative track sections into 100 m segments, employing t-tests for statistical analysis. For our studied section, tamping induced a direct improvement of track quality by significantly reducing the standard deviations of longitudinal level and alignment, decreasing maximum twist values, and increasing the composite track quality index (QS). The paper also compares the two measurement systems, highlighting their combined value in assessing tamping efficacy. Both measurement systems yielded comparable track geometry measures, highlighting the potential of combining frequent data from onboard-mounted systems with regular measurements for maintenance analysis and decision-making.