A sensor unit, in particular a sensor unit in or on a vehicle, for capacitively ascertaining the distance between the sensor device and an object, having an electrode for forming a capacitive system with the object and an apparatus for creating a signal proportional to the capacitance of the capacitive system. The sensor unit has a reference electrode for forming a capacitive reference system with the object, an additional apparatus for creating a reference signal proportional to the capacitance of the capacitive reference system, and an analyzer device for ascertaining the distance by forming a ratio of the signal and the reference signal, the reference electrodes having an electrode shape, which is different from the electrode shape of the electrode.