Daniel Jeans improved the reliability of magnetic field mapping in the key4hep/k4geo repository by addressing a coordinate transformation issue in detector simulations. He corrected the calculation of magnetic field components by ensuring the x-component uses cos(phi) and the y-component uses sin(phi), aligning with standard conventions for extracting values from Br-Z field maps. This adjustment, implemented in C++ using Geant4 and physics simulation techniques, reduced potential systematic errors and enhanced calibration fidelity. Daniel’s work focused on a targeted bug fix rather than feature development, demonstrating careful attention to simulation accuracy and reproducibility within a complex scientific software environment.