An integrated rotation-angle sensor unit in a measuring system for rotation angle determination, with a shaft that is rotatable about an axis of rotation with a transmitter, The sensor unit has a semiconductor layer with a top surface that can be arranged perpendicular to the axis of rotation and has a bottom surface, and two monolithic Hall sensor systems are implemented in the semiconductor layer. Each Hall sensor system has at least a first Hall sensor, a second Hall sensor, and a third Hall sensor, and the three Hall sensors of the first Hall sensor system are arranged on a first circle that is parallel to the top surface of the semiconductor layer and can be arranged concentrically around the axis of rotation.