Ensuring geometric accuracy in precast concrete production is becoming increasingly critical, especially for modular, tolerance-sensitive designs. This is particularly evident in segmental structures with dry joints, where even minor deviations can significantly affect assembly and structural performance. Within this context, a demonstrator for Digital Twin (DT)–based quality monitoring is developed using a modular precast segmental pedestrian bridge as a test case. High-resolution geometric data for individual segments are acquired via structured-light scanning and linked to digital representations of the segments. These are subsequently integrated into a DT of the overall structure, enabling the combined consideration of design and as-built information. The demonstrator illustrates how scan-based data can support the identification of geometric deviations and contribute to quality-related decision-making during production. In addition, the integration of measurement data into a DT environment is outlined, highlighting opportunities for improved traceability and consistency across production stages.