The electric field in a silicon p-n junction has been measured using pixelated scanning transmission electron microscopy. By using a convergence angle of 3.2mrad, a spatial resolution better than 1nm can be achieved leading to a rigid shift of the transmitted beam as it passes through an electric field. By precessing the beam around the optical axis at an angle of 0.1 degrees, the effects of dynamical diffraction can be reduced. This leads to an improved measurement of the electric field from the shift of the transmitted beam. Different algorithms have been used to measure this shift, and template matching leads to a more accurate measurement of the electric field than the often-used center of mass method.