In a method for determining a 3D directional vector between a sending device and a receiving device, the receiving device comprises at least two antenna arrays that each comprise a plurality of linearly arranged antenna elements that are aligned to different orientations. The method comprises receiving, with the antenna arrays, a signal sent from the sending device, sampling, based on the received signal, outputs of each antenna element of each antenna array at a plurality of time instants, determining, for each antenna array, a Propagator Direct Data Acquisition, PDDA, pseudo-spectrum by performing a 1-dimensional PDDA, 1D-PDDA, based on the sampled outputs of the respective antenna array and on a plurality of steering vectors associated with the respective antenna array, determining a maximum of each PDDA pseudo-spectrum, determining an angular quantity () for each antenna array based on the respective maximum of the PDDA pseudo-spectrum, and determining the 3D directional vector based on the angular quantities () of each antenna array and on the orientations of the antenna arrays.