We use a 3D test particle simulation evolved under a potential that includes a Galactic bar. The test particles are given the properties of the disc Red Clump stars in order to convolve with the Gaia errors and to generate a mock catalogue with the stars up to Gaia magnitude, G, 20. In this work, we work in the space of Gaia observables, that is, trigonometric parallaxes. Thus, we show first how the bar structure is mapped in the parallax cartesian space derived from (parallax, galactic longitude). Secondly, we show the effect of the magnitude cut and the introduction o the Gaia errors. Finally, we also consider other possible error sources, for instance from IR photometric distances.