GNSS jamming deployed as an electronic warfare tactic near active conflict zones poses a growing threat to civilian navigation systems. This paper presents a static measurement campaign conducted in Eastern Estonia during a real-world jamming event. During the campaign, synchronized raw In-phase and Quadrature (I/Q) data and Septentrio Binary Format (SBF) receiver logs were collected. Spectral analysis of the raw I/Q data identifies a dominant interference source, whose type and spectral properties are systematically characterized. Cross-layer analysis reveals that, although the observed interference does not cause a complete loss of receiver tracking, measurable degradation is evident in C/N0, tracking loop jitter, and code frequency deviation across affected signals, with a corresponding impact on positioning accuracy. The results further indicate that Galileo Open Service Navigation Message Authentication (OSNMA) is sensitive to the observed interference levels, as demonstrated by satellite-specific authentication failures and a drop in overall authentication availability during jamming episodes, even in the absence of spoofing signals. This finding suggests a previously understudied indirect vulnerability of the OSNMA service under moderate real-world jamming conditions. A multi-metric collaborative detection concept combining pre-correlation domain and receiver-internal features is also discussed to improve detection confidence over single-metric approaches. The complete dataset, including raw I/Q data and SBF logs, comprises recordings of interference observed near a conflict zone, is released as open data to support the development and benchmarking of GNSS interference detection and mitigation algorithms.